"기술정보와 궁금한 것들"에 관련된 조항

This procedure will affect every recorded route, but not the already existing ones, which have to be transferred manually. This last manual method will be explained further at the end of this article.

Scheme of the main screen of Oruxmaps with the most remarkable elements.

Go to Settings → Integration → Upload automatically → Check box Oruxmaps/SICAMI

It’s indispensable to have the corresponding accounts, otherwise either the information will be requested or it will be indicated so through a message.

The step-by-step procedure would be as it follows:

Tap on the “Sidebar” icon (three horizontal lines at the top left corner of the screen). This option is also accessible from “Configure the app” (icon with three dots at the top right corner of the screen.)

Go to “Global settings” tapping on the gear icon.

Scroll down until you find ‘Integration’. Whether all the options are visible or not will depend on the screen resolution of the phone.

Tap on "Integration".

Tap on "Upload automatically".

Check the corresponding box for the app you want to link.

In case the account isn’t configured, the corresponding information for the account on SICAMI will be requested. For Strava, you will need to log in through the pop-up window.

Configure the privacy of automatically-uploaded routes and whether you want the related pictures to be uploaded along them.

These settings can be configured later by accessing ‘Integration’ and selecting the linked app.

Manually upload routes to Sicami or Strava

Routes can also be transferred or uploaded to Sicami or Strava.

In order to do so, you will need to follow these steps:

1. Access the Tracks/Routes list.
2. Tap in the one you want to transfer.
3. Tap on “Properties” on the pop-up window.
4. Tap on the Configuration panel (three horizontal lines) at the bottom left corner of the screen.
5. Select "Upload to".
6. Check "SICAMI" or Strava.

Next, the following steps are shown in a video and various screenshots.

Tap on the NAVIGATION icon. It is also accessible through the “Tracks” button on the right side buttons.

Go to “Manage Tracks/Routes”.

Tap on the desired track/route to open the contextual menu.

Go to “Properties”.

Tap on the configuration panel on the left corner.

Tap on “Upload to”.

Select SICAMI, Strava or the desired app.

##publi##

Energy, Work and Power, some physical definitions

Energy, Work and Power are closely related physical quantities.

Energy

Energy is the capacity of a system to produce work. A system that has a certain energy will not do any work until that capacity is converted into motion. For example, an apple on a tree has a potential energy, but it does not do any work until it falls.

Its unit in the international system is the Joule (joule) which is the work done by a force of one newton whose point of application is displaced by one meter in the same direction.

Work

Work consists of a transfer of energy between systems. In the case of a force acting on a body, its work is equivalent to the energy required to move it. A force acting on a body is then said to do work when it causes a displacement of the body in the direction of the force. Therefore, in a mechanical system, if there is no displacement, the work is zero. This conclusion is not valid for thermodynamic systems, where heat transfers are considered as energy transfers.

Only the component of the force acting in the direction of displacement is considered to do work, in the case of the figure above it would be the horizontal component of the force F.

Work has the same units as energy.

Power

we can define power as the amount of work or energy use we perform in a given time. It is the speed at which we perform work or use energy.Units: watts.One watt of power is generated when work is done that consumes 1 Joule of energy during 1 second of time.. 1 w = 1 joule/ 1 segundo

Graphical interpretation of energy in the power chart

Graphically, energy is the area under the graph of power as a function of time:

Orientation methods. Orientation by watch.

First of all, it is essential that the watch is on solar time or that we carry out the process by mentally setting the hour hand to the corresponding solar time. The official time will depend on the country and the season of the year and usually varies by one or two hours from solar time.

This method is not applicable in the area between the tropics as the result will vary according to the time of year and at certain times the position of the sun will be practically vertical, casting no shadows. Something similar occurs in summer in the central hours of the day and the closer to the tropics.

If we are in the northern hemisphere

If we are in the northern hemisphere, we will proceed as follows: we will keep the watch in a horizontal position, we will point the hour hand at the sun. Next we will imagine a line that passes through 12 and 6 o'clock. The bisector of the angle that the hour hand forms with that 12-6 line will indicate south. Remember that the bisector of an angle is the line that divides that angle into two equal parts.

In the opposite direction you will find the north. To find the east and west we will position ourselves facing north, to our right will be the east and to our left the west.

If we are in the southern hemisphere

If we are in the southern hemisphere, we should point to the sun with the number 12, instead of the hour hand, and in this case the bisector of the angle formed by the line 12-6 with the hour hand will mark the north.

South will be in the opposite direction.

If we don't have a needle clock

If you don't have a clock with needle but you know the time, you can always draw it on a piece of paper, on the ground or using twigs.

In 1687 the English physicist Isaac Newton published three laws or principles to describe the motion of bodies in an inertial reference system, relating force, velocity and motion of bodies.

These three laws are the following

- First law or law of inertia.

- Second law or fundamental law of dynamics.

- Third law or principle of action and reaction.

 

Newton's First Law: Law of Inertia

The first law or law of inertia postulates that a body at rest or moving in a straight line with a constant velocity will remain in that state unless an external force is applied.

In case more than one force acts, if the sum of the forces acting on the body is equal to zero, then the change in its velocity will also be equal to zero. That is, its velocity will not change.

This principle had already been observed earlier by Galileo Galilei.

We are quite familiar with the effects of this law because we perceive them daily, for example, when we travel in a vehicle that brakes we notice how our body tends to continue at the speed at which we were traveling or when it takes a curve it tends to continue in a straight line. It is also responsible for falls when we stumble while walking, running or pedaling.

Newton's second law: fundamental law of dynamics

F = net or resultant force of all the forces acting on the body.
m = mass of the body in kg.
a = acceleration in m/s2 (meter per second squared).

That is, the greater the force applied to a body, the greater its acceleration and, on the other hand, the greater the mass of a body, the greater the force required to accelerate it.

Newton's third law: action and reaction principle

Newton's third law or principle of action and reaction states that every action in one direction generates a reaction of the same intensity, but in the opposite direction.

The force of body A on body B, F(A-B), which we will call the action force, is equal to the force of body B on body A, F(B-A), which we will call the reaction force. The reaction force will have the same direction and intensity as the action force, but in the opposite direction.

With the effects of this law we are also quite familiar in our daily life, for example, when we move any heavy object by pushing it, i.e. applying force on the object to move it, we perceive a resistance of the object which is the reaction force of this object on us.

 

The law of Universal Gravitation or law of gravity

This law describes how two bodies with mass interact and attract each other, and states that the intensity of the force of attraction between these two bodies is proportional to the product of their masses and inversely proportional to the distance between them squared.

In other words, the stronger the mass of the bodies and the closer they are to each other, the stronger the force of attraction will be, and the stronger the force of attraction will be, decreasing with distance.

The formula is as follows:

Where::

F is the value of the force exerted between the two bodies along the line joining them.

m1 is the mass of the body 1

m2 is the mass of the body 2

r distance between the centres of mass of the two bodies

G is a constant, the universal gravitation constant, and its value is

The value of G is obtained experimentally and, as we can see, it is really tiny.

Calculate the force with which the Earth attracts you

If you want to know how strongly the earth attracts you, you need to know your mass in kilograms, the mass of the earth and its radius, which is the distance that separates you from the centre of mass of the planet.

If your weight is 75 kilos:

Approximate mass of the Earth: 5.98 × 10^24 kg

Average radius of the Earth: 6.37 km = 6,370,000 metres

Torque of force on the pedal

When pedaling our force is applied to the pedal and transmitted to the axle through the crank, which acts as a lever. The application of the force will cause a rotation with which we will observe a "torque" or "torque".

We can define torque as the ability of a force to rotate an object when applied to it.

The value of the torque of a force can be calculated as the product of the value of the force applied at a point, multiplied by the distance from that point to the torque axis. Its unit is the newton per meter.

T = F · d

F = force on the pedal

d = distance to the center of rotation (distance pedal axis - crank axis)

Tangential and radial components of pedal force

But this would only be valid for forces applied perpendicular to the distance. Since the force can be applied at different angles, depending on the thrust position, we will extend the formula as follows:

T = F · d · sen (a)

Where a is the angle of application of the force with respect to the line joining the point of application and the center of rotation. The angle whose value is less than 90º will always be taken. This is equivalent to decomposing the force exerted on the pedal into two components:

• a tangential component Ft, which is tangent to the circumference drawn by the pedal Ft = F sin (a)

• a radial component, Fr in the direction of the connecting rod. Fr = F cos (a)

The tangential component will always be perpendicular to the connecting rod and is the one that produces useful torque. The radial component Fr will only compress or stretch the connecting rod.

Pedalling efficiency and effectiveness

The "useful" force will therefore depend on the angle of application of the force on the pedal and this in turn depends fundamentally on the position of the cranks.

Assuming that we pedal pushing down vertically, if the crank is also in a vertical position at "12-6 o'clock", the Ft component perpendicular to the distance line will be zero and the applied force will not cause any rotation.

Mathematically:   T = F · sin (0) = F · 0 = 0

At the other end, if the connecting rod is horizontal at "3-9", the perpendicular Ft component will coincide completely with F and all the applied force will cause torque and therefore rotation.

Mathematically:   T = F · sen (90) = F · 1 = F

From all of the above we can conclude that the greatest efficiency in pedaling would be obtained by applying the force on our pedals always describing the tangential direction (perpendicular to the crank) which would generate 100% efficient torque, although this seems physiologically complex and would require control of the motricity of both legs beyond the reach of a standard human being.

In this article we discuss navigation concepts and look at the differences between course and heading.

Course, true course, magnetic course y desired track

We will call course the trajectory to follow, it is the planned or desired route between two points A and B. It could be identified as the straight line that joins both points.

The true course (TC: True Course) would be the angle in degrees between the true or geographic north and the course. It is measured from the geographic (or magnetic) north in a clockwise direction.
Since the meridians on a map all point to true north, they can be used as 0 degree references to measure angles to true north.

Since the geographic north and the magnetic north pole do not coincide (see the article "Magnetic declination" in the "Additional information, curiosities and glossary of terms" section of this site) we will also define the magnetic course (MC: magnetic course) as the angle in degrees between magnetic north and the course. It is measured from magnetic north and also clockwise.

In this case, the meridians cannot be used as references of 0 degrees, instead we will use the compass.

In some environments, the Desired Track (DTK) refers to the true course and the magnetic course interchangeably , depending on the north used as reference (geographic or magnetic).
 

Heading, true heading, magnetic heading, drift y drift correction angle

We will call heading (Heading) the angle formed by the north (geographic or magnetic) and the longitudinal axis of the aircraft (in the case of an airplane it would be where its nose points). It will be called true heading (TH: True Heading) if the angle is taken with respect to geographic north and magnetic heading (MH: Magnetic Heading) if it is taken with respect to magnetic north.

The heading does not necessarily coincide with the course since the aircraft or ship can change its orientation to counteract a crosswind or water currents. In the case of airplanes it is usual that, to maintain a constant course, the aircraft turns its nose slightly towards the wind.
##publi##
The angle formed between the desired course and the heading of the aircraft will be called the drift correction angle (WCA: Wind Correction Angle) since, by definition, drift is the deviation of a ship from the established heading, for effect of wind, sea or current. 

It's basically the difference between where the ship is pointing and where it's actually moving. This angle is usually calculated by the flight computer. If the wind comes from the left, the correction angle will be negative. If it comes from the right it will be positive.
 

Spokes on wheels with disc brakes and rim brakes

There is an immediate visual difference between road bike wheels that use disc brakes and those that use rim brakes and it is not only in the pads or the discs, would you know which of these pairs of wheels (same brand and model) ) corresponds to a disc brake and which one to a rim brake?

The difference is evident and it is in the distribution of the spokes of the front wheel.

Traditionally the spokes of the rear wheel have been placed with a different crossover than the front wheel. In many cases, the spokes of the front wheels had an exact “radial” layout, that is, they went from the center of the wheel (the hub) outwards and reached perpendicular to the rim.

Mechanical stresses on the wheels

The reason for this is that the mechanical stresses to which the front and rear wheels are subjected are different, especially the stresses on the transmission. Specifically, the rear wheel must transmit to the ground the torque (moment) of the force of the chain on the sprockets, which in turn is transmitted to the hub and from the hub to the rim and tire through the spokes. So the spokes are the “pillars” that transmit the spin from the axis of the wheel to the ground.

As the ground opposes resistance to the advance and rotation of the wheel, mechanical stress is generated on the spokes.

Mechanical stresses on wheel spokes

The main stresses to which a spoke is subjected will be compression-traction and bending, but how do these affect the mechanical behavior of the spokes? Compressive/tensile stresses act in the same direction as the major axis of the radius and will tend to shorten it (compression) or lengthen it (tensile). Bending stresses are the result of forces that act perpendicular to the main axis and will tend to bend it, so they are the ones that will have the greatest effect on the radius bending. We must consider that the ends are not free because in this case they will produce rotation and/or translation movements. We can imagine that the radius is "momentarily" fixed at the point of contact with the ground and imagine it as a rod fixed at that end. The axle-hub of the wheel is applying a force on that radius in the opposite direction.

If we think about how much force is necessary to deform a rod of any metal, we surely conclude that it will almost always be easier to break a pencil by holding it by the ends and bending it than by resting it on the table and pressing on one of the ends.

Let's see how the radios are affected by these forces according to their disposition.

A spoke that is perpendicular to the ground at the point of contact will be subjected to forces in the opposite direction at each of its ends that will almost exclusively cause bending stresses, which are those that have the greatest effect on the spoke bending. In the case of a “crossed” radius, at the moment of contact with the ground, the force applied by the bushing has a bending component and an axial compression component, with which part of that total force will be absorbed by the material. Compressive forces have a much less significant bowing effect on a rod.

Another of the forces that act on these same planes of a wheel are the braking forces and let's not forget that effective braking occurs at the point of contact of the wheel tire with the ground. In the case of a rim brake, the force applied to stop the wheel is applied to the rim and this transmits it to the tire, located very close, so it is the rim that supports almost all the efforts with very little repercussion on the wheels. spokes. However, in the case of disc brakes, the braking force is applied to a disc attached to the hub, so this force must be transmitted to the rim and tire, the spokes being those force transmission elements. This is one of the reasons that today the front wheels of road bikes that mount disc brakes have abandoned the radial arrangement and adopted the traditional crossed spoke arrangement of the rear wheels as well.

Could this be the real reason for the broken spokes on Wilco Kelderman's disc brake wheel at the 2022 Giro d'Italia, when he lost almost 11 minutes on the descents? Some attributed it to the "heat" of the spokes due to the disc brake, although it seems difficult that so much heat could be transmitted from the disc to the spoke and that it would destroy it. Perhaps those spokes simply couldn't withstand the intense and repeated flexing stresses of hard, long downhill braking.

Wheelbase. Influence on the character and behaviour of the bicycle.

The distance that exists between the axes (hubs) of the wheels, measured from their center, is also called "battle", in English wheelbase and is a very determining element in the character of the bicycle. The shorter the wheelbase, the more reactive, mousetrap in curves and nervous the bike will be, also more rigid and therefore less comfortable, while longer wheelbases will make the bike more stable and comfortable, especially on straight terrain and at higher speeds. but also slower in their reactions. The wheelbase directly influences the maximum turning radius of the bicycle

The wheelbase obviously depends on the rest of the elements of the bicycle and its general geometry, although some of the most determining elements are the size, the angle of the steering and the advance of the fork or arrow. The following image shows how a offset fork (top image) will increase the wheelbase while a straight fork will decrease it.

The wheelbase of road bikes is noticeably shorter than that of mountain bikes. In the latter, the battle is longer in order to be able to ride better on more demanding terrain. This difference in length can be 100 mm. or more.

##publi##

There are many more elements that determine the behavior of a bicycle and their influence is not individual, it already depends on the rest of the components, including the cyclist, and in any case, it would be the result of the combination, not necessarily the sum, of all of them. Let's take into account that the bicycle, unlike a car or motorcycle, has a much smaller total mass but, and this is very important, the distribution of these masses is very different. The element with the greatest mass in the bicycle-cyclist set is the latter which, together with its position, will cause the center of mass of the set to be at a higher relative height than in automobiles or motorcycles.

Let's not forget that the vertical distance from the vehicle's center of mass determines the moment of the forces exerted on the vehicle, including its "rolling moment". These moments are all the greater the greater the distance from the center of mass to the ground. This is one of the reasons why it is advisable to lower the position of the body when taking curves, because stability and security will be gained, being able to trace at a higher speed.

Regarding the geometry of the bicycle, the "bottom bracket offset", also known as "bottom bracket offset" is the one that determines the position of the center of gravity to a greater extent. This is the vertical distance between the horizontal of the bottom bracket and the horizontal of the hubs of the wheels. But we will talk about this parameter in another article.

The rope

Guide to useful knots If there is an element that can truly be useful when we move in natural environments, that element is, without a doubt, the rope. Throughout our extensive experience playing sports in natural environments, we have encountered circumstances on multiple occasions in which it was necessary to use ropes to solve any eventuality. Obviously when climbing or progressing via ferrata it is an essential element and its knowledge and management is a matter of maximum safety. But it has also proven useful in many other conditions, especially in emergency repairs or simply to secure items to prevent loss.

You can always find somewhere to go well equipped.
 

Warning! some sports activities require knowledge and mastery of the specific technique, please do not assume unnecessary risks and seek advice from an expert professional who knows the risks and techniques of the activity
 

The knots

But for a rope to be really useful it is necessary to modify its shape properly, for this we will use knots . By definition, a knot (from the Latin nodus) is a loop that tightens and closes so that with difficulty it can be released on its own, and the more one pulls on either of the two ends, the more it tightens.

The main characteristics that a knot must meet are: that it be easy to make, that it be easy to undo after use with a load, that it be resistant and that it serves the purpose that we are going to give it.

Rope and knot parts

First, some definitions...

Cape: A cape is another name for a rope.
Chicote: it is the end of the rope, the tip.
Sign:is the rest of the rope with respect to one of its whips.
Sine: it is a loop, loop or fold of the rope. It also occurs when crossing the whip on the firm.
 

Cordino: We will call the strings of smaller gauge, 4-8 mm.

Some common knots

Eight knot

It is the most used knot in climbing to join the harness to the rope. It is a very safe and resistant knot, easy to execute and easy to untie when it has been under load. There are two ways to build it that will be used according to the case. The basic form is built as shown in the figure:
 

Knot of eight per sine

It can be used as long as the anchoring element allows its opening, as in the case of carabiners, maillons, etc. since we will start from a closed loop. To do it we will make a simple knot but giving an additional turn.
In the first step we will make a loop or trough that we will pass over and around the pavement, going around behind it, so that another loop will be created, in this case formed by a double rope. Subsequently we pass the end of the loop through the interior of the formed sinus. It only remains to tighten and "comb" so that it remains as shown in the last figure.
 

Knot of eight by whip

We will use this method when it is necessary to pass the whip through the anchoring element when it is closed, as in the case of the harness, rings, etc. For its construction, we start from the basic figure-of-eight knot and we will pass the whip through the ring, harness... Next, we will follow the route of the base knot in the opposite direction with the whip.
 

Bowline knot

Another of the most used knots in climbing and rescue, also for lifting loads. It is a knot that does not slip and is easy to make and undo. This knot should only be used under load as it stays open as soon as the tension is removed.
It begins by making a simple loop, in the lower figure we have passed the free end over the firm. Next, pass the whip through the loop from the bottom up and go around the firm from behind. Pass the whip through the loop again, but this time from top to bottom. Tense. To increase the security of the knot, preventing it from coming undone easily when it is without tension, it is advisable to finish off the excess end with an additional simple knot.
 

The usual thing is that the anchor point is closed, as in the case of a ring, or that the open part is inaccessible, as in a tree, a high pole, etc... so it is convenient to practice the execution by whip such as is shown in the following figures.
 

Clove hitch knot

It is usually used to secure the rope to a pole, bar or another rope, which is why it is widely used for tent supports. It is a knot that will tend to loosen if it is subjected to stresses from different directions.
 

As in previous cases, if the anchor point is closed or the ends are not accessible, it will be necessary to apply the whip construction method.
 

Double fisherman's knot

We will use it to join two ropes together or to close a rope or cord in the shape of a ring. The latter will be essential to be able to make some of the knots that we will mention later.
 

Skylark knot

Very simple knot for direct anchoring on rings or posts. It is usual to do it with a loop closed in a ring.
 

Although it is also possible to do it with an open end. It is advisable to secure in a knot by passing the excess short end inside.
 

Roman knot

It is a knot in which the ropes will come out in opposite directions creating a directional loop aligned up or down with respect to the main rope line. It has application in hoisting, hoists, rope tensioning, stirrups, ….
 

Figure-of-eight knot

Similar to the Roman knot, but in this case it is based on a figure-of-eight knot. The strings will also come out in opposite directions creating a directional loop aligned up or down from the main string line. The application will also be in hoisting, hoists, rope tensioning, stirrups, ….
 

Prusik knot

It is a self-locking knot for which a cord is used in a closed ring loop. It is used on another main rope with a larger diameter. The knot slides easily when not under load, but locks as soon as it is under tension as it pinches the main rope. It is used as a method of self-belaying in rappelling, to go up on a rope, descend equipment... It is built by surrounding the rope as shown in the figures, successively passing one of the ends under the main loop. It is very important to fit the knot on the rope well before using it. Being a symmetrical knot it acts in both directions.
 

Machard's knot

It is another self-locking knot for which a cord will also be used in a closed ring loop. It is used on another main rope with a larger diameter. The knot slips easily when not under load, but locks as soon as it is put under tension by pinching the main rope. It is used as a method of self-belaying in rappelling, to go up on a rope, descend equipment... It is built by surrounding the main rope as shown in the figures to finish passing the lower end through the upper loop. It is very important to fit the knot on the rope well before using it. This knot, unlike the Prusik, only acts in one direction.
 

The diversity of existing knots is immense and would give rise to a specific treatise that is not the objective of this site, we invite you to delve into this exciting subject.

GPS (Global Positioning System)

It is a system that allows to locate an object that is on Earth with high precision. To do this, the receiving device locates at least four satellites from the satellite network placed in orbit, from which it receives signals that indicate the identification and the time of the internal clock of each satellite. With this information the distance to the satellite is calculated. Knowing the distance to these satellites and by the "trilateration" method, the GPS device can determine the position on the Earth's surface.

With three satellites, the device is capable of determining the latitude and longitude of its position, that is, its position in two dimensions. By adding a fourth satellite, it will also be able to calculate the altitude, obtaining the position in three dimensions. The signals emitted by each satellite form a sphere with the satellite in the center, the point of intersection of all the spheres is what determines the position where the GPS receiver device is located.

As a curiosity, the satellites transmit on three different frequencies of the radio frequency L band (1000 – 2000 MHz) of the electromagnetic spectrum.

Other Global positioning systems

There are currently four major global positioning systems:

GPS : The best known and currently used is GPS, which is a system owned by the United States Department of Defense and consists of three parts: orbiting satellites, base stations and receivers. Its coverage extends to the whole world. Its real name is NAVSTAR (Navigation Satellite Timing and Ranging).

GLONASS (GLobalnaya NAvigatsionnaya Sputnikovaya System): It is Russia's state-owned positioning system and also has worldwide coverage.

Galileo : Galileo has been developed by the EU as an alternative to GPS and GLONASS.

BeiDou : It is the system created by China and has worldwide coverage although it offers greater precision in Asia and the Pacific. BeiDou means Big Dipper in Chinese.

There are also other systems, although their coverage is only regional, such as the NavIC system in India or the QZSS system in Japan.

Geographic coordinates

Spherical angular coordinate reference system to represent locations on earth. At least three values ​​will be needed to represent a location: one for the horizontal position, one for the vertical position, and a third indicating the distance to ground level, which is identified as sea level. The values ​​of horizontal and vertical position are usually given in sexagesimal degrees, since these are angles whose center is the Earth.

Meridians and parallels

The terrestrial sphere is divided with imaginary lines called meridians and parallels . 

Meridians

Meridians are lines that run from the North Pole to the South Pole. The prime meridian, zero meridian or Greenwich meridian is the imaginary line that joins the north and south poles passing through the town of Greenwich in England, the rest of the meridians take this as a reference. To the east the meridians are taking positive values ​​up to 180º while to the west the values ​​taken are negative.

Parallels

Parallels are lines from east to west, are perpendicular to the north-south axis and are parallel to the Equator. The equator is parallel "0".

Latitude y Longitude

Latitude

The latitude of a point on the earth's surface is the angle between the plane passing through the equator and the line passing through the point and the center of the earth. All points with the same latitude form imaginary circles that are "parallel" to each other and parallel to the equator, which is the larger of the "parallels."

Longitude

The longitude of a point on the earth's surface is the angle between the plane passing through the Greenwich meridian and the plane of the meridian passing through the point. All points with the same length form semicircles that pass through the poles similar to the segments of an orange.

Representation of geographic data in two dimensions, contour lines

Isolines are used to represent the distribution of a variable (temperature, atmospheric pressure...) on a surface. The isolines are lines that join points with the same value on the surface, the value can be the one that is chosen, temperature (isotherms), pressure (isobars), precipitation (isohyets).

The isolines that join points of equal altitude of the terrain are known as "contour lines" and allow the representation of the terrain surface in two dimensions.
 

Types of contour lines

On cartographic maps we will find two or three types of contour lines represented, normally in brown.

Contour lines

Are the thinner lines.

Master contour lines

Are thicker lines.

Auxiliary contour lines

Are thinner Dashed Lines

Additional numerical information

Master curves display a number that represents the absolute value of altitude along that line. The numbers are oriented so that the top of the number indicates which way the altitude value increases.

If between two master lines, for example 900 and 950, we find four level curves, these will divide the space into 5 parts and we will interpret them as the intermediate values ​​between 900 and 950, that is: 910, 920, 930 and 940.

If a master line does not have an indication with a number, probably due to lack of space in the visualization, we will interpret that it follows the same interval as for the rest of the master lines.

The summits or tops are the points of the terrain of maximum relative altitude and are also shown on the map. In the following example we can see that there are several summits (indicated by a dot and numbers in black) of 999, 984, 883, 887, 1051... meters.
 

More information

The gradient

The gradient or degree of variation of the altitude is always perpendicular to the contour. When the lines are very close to each other, they indicate that the altitude variation is very fast, which means that the altitude increases or decreases sharply.
The distance between contour lines will depend on the scale of the map and is usually between 50 and 100 meters for the main lines and between 10 and 20 meters for the intermediate (thinner) lines.

The scale

the scale of a map indicates the equivalence between the real distance and the distance represented on the map. For example, a scale of 1:10,000 means that one meter on the map equals 10,000 meters in reality, or that one centimeter on the map equals 10,000 centimeters in reality. Larger scales will cover more of the terrain but the detail will be less.

The legend

If the map has a legend or documentation of the symbols used, it is convenient to review it as it will provide us with a lot of information about the units of measurement used, the colors, orientation, scale and elements represented.

In the map of the previous image we can see that there are some non-permanent streams or rivers marked with a broken blue line.
 

also an olive grove on the left bank, below (at a lower altitude) a leafy area and scrub areas.
 

Types of maps. Classification criteria

Maps can be classified according to different criteria, in our case we will classify them according to the content and mode of representation.

Maps by content type

Depending on the mode of representation of the terrain we can distinguish between

Raster maps

Raster maps consist of georeferenced images, that is, it is an image file to which coordinates are assigned so that it is displayed in the correct location when opened with an application. They can be built with standard image formats (jpg, bmp...) accompanied by a calibration file, although there are specific formats for digital cartography
 

Maps of this type can take up a lot of space in memory, so they are usually available as mosaic maps in which the entire map is divided into smaller pieces (tiles) to handle only the parts of the map corresponding to the area to be viewed. use.

Vector maps

This type of map is composed of vector objects such as polylines, polygons or points that contain additional information such as color, labels, type of terrain. These elements and other information will be arranged in layers that will be displayed based on the display options setting or zoom level. These maps may contain information that allows an application to automatically calculate routes.
 

DEM: Digital Elevation Model

They are maps that contain only information about terrain altitude. They will normally be used in combination with another map to render it in 3D and assign altitude to route points and waypoints. (See section "Information on data calculation methods" on this site)

Maps according to the mode of representation of the terrain

Depending on the way the terrain is represented, we can distinguish between:

Topographic maps

Raster or vector map that represents the terrain using contour lines, colors and graphic symbols to show information about the area such as geographical features, roads, trails, sources...

Orthophoto

They are raster maps consisting of aerial images of the terrain with orthogonal projection (perpendicular to the surface). To avoid distortions due to the point of view of the camera, the aerial photographs are rectified to adapt them to the shape of the terrain.
 

Road maps

These are vector maps especially oriented to urban and interurban navigation. Useful elements for the motorist or road user are highlighted.
 

Carthographic projections 

A map is a two-dimensional representation of the earth, which has three dimensions, the transition from a three-dimensional representation to two dimensions is known as a projection.

In order for there to be a correspondence between the points on the curved surface of the earth and those on the flat surface of a map, a grid is used with x and y coordinates obtained from the longitude and latitude coordinates through different mathematical calculations. This causes that there is inevitably a deformation when making the projection, so it will be depending on what parameters we want to read (distances, surfaces or angles) that one or another of the available projection systems will be used, making a projection that correctly represents impossible. all three simultaneously.

Based on this we can distinguish three types of projection

Projections according to conservation of distances, surfaces or angles

Equidistant projection: 

where distances are preserved

Equivalent projection: 

where surfaces are kept

Conformal projection: 

where the shape or relationship of angles between points is preserved.

To improve the result of the projections, geometric surfaces can be used that will later be lowered in the plane. Let's see some of the most common:

Projections on geometric surfaces

Cylindrical projection. 

It is obtained by placing a tangent cylinder to the terrestrial sphere at Ecuador. The Mercator projection is the best known cylindrical projection. The meridians and parallels will be perpendicular in the projection, the distance between the parallels will increase as the latitude increases. This will produce a larger deformation the further away the north or south position is from the Equator. The Equator will be the only line where the scale will be preserved. The territories and countries located further north will appear larger than life and the poles are not represented as they would be at infinity. Although this system causes the areas near the poles to be greatly distorted, it is useful for navigation since it is a type of "conformal" projection, that is, it preserves the angular relationship between points.

The Transverse Mercator projection

The Transverse Mercator projection is a variant of the Mercator projection where the meridians are expanded to the east or west of the Greenwich meridian. The meridians are represented by curved lines parallel to each other and convex towards the equator. In this case, the distortions are greater the further away the position is from the Greenwich meridian and this will be the only line where the scale will be preserved.

The Universal Transverse Mercator Projection (U.T.M.)

The Universal Transverse Mercator Projection (U.T.M.) is another projection system, based on the transverse projection, which divides the globe into 60 sectors or zones along the Equator (each sector covers 6 degrees of longitude). Each zone has a central meridian and the intersection of this central meridian with the Equator is established as the "x" and "y" origin of the zone.

Conical projection

Meridians and parallels are projected onto a conical surface tangent to the vertex of the cone on the axis formed by the poles. The meridians will become straight lines starting from the pole and the parallels will become concentric circles centered on the poles.

Types of clouds according to their shapes, colors and altitude.

High clouds (above 6,000 meters)

Cirrus clouds:

White, somewhat transparent, do not have interior shadows or cast a shadow on the ground. They form long, thin filaments, sometimes aligned like tufts of hair. They are formed mostly by ice crystals and usually produce halos with the sun or moon. With few and fine cirrus clouds, the weather will be stable, but it will probably tend to get worse if they begin to acquire volume and density.

Cirrocumulus:

Similar to cirrus clouds but more dense, forming an almost continuous layer with rounded shapes. They also do not have interior shadows and are completely white. They usually anticipate the arrival of a cold front. They can also form halos.

Cirrostratus:

Appears as a white and transparent layer like a veil that covers part of the sky without a clear structure. They usually present elongated striations of a certain width. They form halos. They usually appear before a large increase in cloudiness and worsening weather.

Medium clouds (between 2,000 and 6,000 meters)

Alto cumulus:

They are white and bluish gray. With inner shadows. They are made up of water and ice. They are denser and more compact and have a varied appearance, lenticular, globular, stratiform. They do not produce precipitation, but anticipate the arrival of bad weather due to storms.

AltoStratos:

Forms a translucent gray or bluish sheet with dense clouds mixed with finer areas. They allow the passage of the sun that will appear as a luminous disk. They are usually a harbinger of fine rain and a drop in temperature.

Nimbostratus:

Dark gray in color with more or less opaque areas. They block the sun completely. They give precipitation with a high probability of light or moderate character, both rain and snow.

Low clouds (between 0 and 2,000 meters)

Stratocumulus:

White in color with gray areas of different intensities. Large size and notable vertical development. These types of clouds do not usually cause precipitation.

Strata:

Gray in color and poorly defined, it looks like fog since they are low above the ground and can cause a light drizzle.

Cumulonimbus:

They are clouds of great vertical development, being able to cover from the lowest level to the highest. They are dense and their upper part sometimes extends into a large plume, the lower part being dark in colour. It usually produces showers and electrical storms. It is made up of large water droplets and ice crystals on top.

Cumulus:

Large in size, flattened at the base and with large bumps at the top. White color with abundant leftovers. They tend to be typical in stable and sunny weather and do not present a risk of precipitation although they can grow to form cumulonimbus clouds when there are strong updrafts and high humidity.

Altitude, Height and Elevation

It is common to use the terms altitude and height interchangeably to refer to a location. Next we will recall the definition of these terms.

Height is the vertical distance of a body from the earth's surface (the ground or the sea).

Altitude is the vertical distance of a body from sea level, regardless of whether the object is on the earth's surface or above it (plane, drone, ...)

Elevation is the vertical distance to sea level of a point that is on and in contact with the Earth's surface.

In the following graph, we see that the green point is located at a certain altitude and at a certain height, while the yellow point on the ground surface is at a certain altitude, but its height is zero since it is touching the ground. The land on which it is located is at a certain elevation.

In certain cases the values ​​may coincide, although we will be referring to different concepts. For example, for the yellow dot the elevation matches the altitude and if the body were flying over the sea, its altitude would match its height.

Unevenness and slopes of a route. Positive, negative and accumulated unevenness.

The difference in level, by definition, is the difference in height between two or more points. The zero level point will be the point where we start the route, regardless of the height of that point at sea level.

The accumulated difference in altitude will be positive if the final height is greater than that of the starting point (we have accumulated meters by ascending) and negative if the final height is less than that of the starting point (we have accumulated meters by descending). If the starting point and the end point coincide, the accumulated difference will be zero.

Strictly speaking, to calculate the accumulated gradient of a route, we will add the positive gradient and the negative gradient. For example, on a circular route that climbs a 500-meter pass and has the same departure and arrival point, the positive difference in altitude will be 500 meters and the negative difference in altitude will be another 500 meters, so the accumulated difference in altitude will be 1000 meters. On any route with the same starting and finishing point, the positive accumulated gradient will be equal to the negative accumulated gradient.

As the routes usually do not usually only go up or down, but there are concatenated ascent sections and descending sections, the positive accumulated difference will be the sum of all the height gains and the negative one will be the sum of all the height losses. Therefore, it will not coincide with the height gained or total altitude gain, which is the difference between the highest level and the lowest level of the route.

Example: We leave point A with an altitude of 500 meters above sea level and end at point F with an altitude of 600 meters above sea level, passing through intermediate points B, C, D and E.

We add all the altitude gains in the ascending sections:
A-B: 600-500 = 100
B-C: 1000-600 = 400
D-E: 1300-700 = 600
Positive cumulative difference: 1,100 meters

We add all the altitude losses in the descending sections:
C-D: 700-1000 = -300
E-F: 600-1300= -700
Negative accumulated gradient: -300 – 700 = -1,000 meters

Total accumulated slope: 1,100-1000 = 100 meters.

In cycling, when we talk about “accumulated slope”, we usually refer to the positive slope, as it gives a better idea of the difficulty of the route.

Slopes of a track

To determine the difficulty of a route, as important as knowing the unevenness is knowing the slopes of the different ramps. The slope is the relationship between the distance ascended vertically and the horizontal distance traveled to ascend it. A quick and simple formula to calculate the average slope of a section would be the following as long as the vertical distance and the horizontal distance to the point of ascent are known:

Slope (%) = Vertical distance x 100 /Horizontal distance

According to known data: distance traveled, elevation angle, vertical distance, etc. There are other methods in which trigonometric calculations are applied.

Weigner's Law or principle of supercompensation

When we do physical exercise or any type of continuous and repeated efforts over time, our body undergoes a series of adaptations that will produce an improvement in our strength and performance. It is the way in which you will prepare to face similar or greater efforts in the future while minimizing possible damage.

This process is not instantaneous, it requires a repair and regeneration time. When applying a stimulus, effort or workload we will suffer an initial decrease in our performance or effort capacity as a consequence of the tiredness and fatigue of our muscle fibers. After the rest, essential in any training plan, there will be a recovery process that will not only return us to the level of performance prior to the exercise, but will also increase it. If the effort is not repeated, the level of performance will drop again since our body will always tend to save energy.

Graphically we could represent it as follows:
 

Obviously, a specific effort will not be enough for any improvement to take place and it will be necessary to repeat the efforts (training) so that the state of fitness acquired is not only not lost but also improved. In short, the accumulation of stimuli is necessary to achieve performance improvement.
The principle of supercompensation or Weigner's law shows us how our physical condition would evolve with the accumulation of training.
 

On the other hand, the training must increase its intensity and/or duration so that there is no stagnation of evolution.

Another obvious conclusion in view of the graph is that rest and correct recovery are essential to obtain the desired results, allowing the body to repair damaged tissues and the necessary physical and metabolic adaptations.

Curve and power profile in cycling

The power profile in cycling is a graphical representation of the average power values ​​obtained by the athlete during certain periods of time making an effort.

By average power we understand the arithmetic mean of the power generated in a period of time and it will be obtained by dividing the watts of the entire session by the time spent. Normally it is a data that will automatically provide the potentiometer.

In general, certain certain or critical periods of time are used because they will provide information corresponding to different physical capacities that we will develop in another article, the most characteristic are:

Power in 5 seconds: indicates the capacity for maximum efforts or maximum anaerobic capacity.
Power in 1 minute: indicates the anaerobic capacity.
Power in 5 minutes: indicates the Maximum Aerobic Power (MAP) or maximum oxygen consumption (VO2max)
Power in 20 minutes: indicates the power in the vicinity of the anaerobic threshold
Power in 60 minutes: Also known as Functional Threshold Power or FTP. It is an indicator of the maximum power that we would be able to develop during a period of one hour.

Without going into describing the energy systems used by the body to supply energy to the muscles, we will limit ourselves to briefly describing some of the concepts mentioned:

Aerobic and anaerobic effort

We will call it an aerobic effort to that effort of prolonged duration in time and that is carried out at a moderate or low intensity and therefore sustainable. The circulatory system is capable of providing sufficient oxygen for energy-producing cellular chemical reactions.

On the other hand, an effort of an anaerobic nature is known as one that has a high intensity and that is carried out during a short period of time. Because this effort is very intense, the oxygen available to the cells is limited by exceeding the supply capacity of the circulatory system, so the energy production system in the cells will be different. These efforts will only be sustainable for short periods of time. 

Maximum Oxygen Volume

VO2max is the "Maximum Oxygen Volume" and represents the maximum amount of oxygen in milliliters that a person consumes each minute and for each kilogram of body weight (ml/kg/min) and gives an idea of ​​the efficiency with which our body uses the Oxigen. It is therefore a measure of our aerobic capacity and the resistance of our cardiovascular system. It is a value that has a great genetic dependency although its improvement is possible within certain limits.

Returning to the subject of the power curve, there is specific software for training that automatically provides this curve and there is also abundant literature about its interpretation, the methods for obtaining the data, etc. On this occasion we only want to expose what is the basis for the elaboration of the power profile in a manual and simple way so that you know its fundamentals.

It is necessary to point out that, in order to correctly compare the curves of different athletes, or your own over time, the correct thing would be to have the power data based on the individual's body weight since it is not the same to develop 300 watts weighing 50 kilos than developing 300 watts weighing 80 kilos, especially when it comes to ascents, in the case of the heaviest athlete, his ascent speed will be less for the same power developed. This power per kilo is obtained simply by dividing the absolute watts by the kilos of the athlete's weight.

Elaborating a cyclist's power profile

To create a power profile, it will be enough to obtain the average power developed in the different measurement time intervals.

Example: We will create a table with the average power values ​​obtained in the different time intervals.
 

We will build the graph where on the x axis we will represent the time and on the y axis the power.
 

In order for the graph to show in a more detailed way the values ​​for smaller time intervals, 1 second, 5 seconds... that are very stacked, it will be convenient to represent the x-axis on a logarithmic scale.
 

In another article we will make a more detailed analysis of the information provided by the power profile about the athlete's abilities and, above all, the areas where improvement is possible depending on their objectives.
 

BCD or bolt circle diameter of a bicycle chainring

BCD bicycle chainrings The BCD (Bolt Circle Diameter) or bolt circle diameter of a bicycle transmission chainring is the diameter of the imaginary circle that passes through the center of the bolt holes, provided they are arranged following a circular and equidistant pattern.

Common measurements in mountain biking are BCD 104 and BCD 94 and BCD 96 and they come with four or five holes.

When the chainring has four holes, getting your BCD is as simple as measuring the distance between the centers of two opposite holes.

When the plate has five holes, the process will be somewhat more complicated, but not excessively. In this case we will take the measurement, in millimeters, of the distance between the centers of two adjacent holes and we will carry out the following calculation:

56 x distance-centers / 32.9.

For example, if the measurement is approximately 55 mm (it will be difficult to find the exact center of the hole), we will have: .

56 x 55 / 32.9 = 93.6 which we can round to 94, with which the BCD will be 94.

Mathematical foundations and calculation method for any distribution

For those who are curious about where the previous formula comes from and who also want to be able to calculate the BCD of any regular distribution and circular of screws, bolts or their holes, it is not necessary more than the application of basic trigonometry.

Knowing that the circumference has 360º, if the plate has 5 equidistant holes, the angle formed between any two of those holes will be the one that results from dividing 360 by 5, that is, 72º

Observing the following figure we see that we can obtain all the necessary elements for our calculation:

On the one hand we have the radius of the circumference, taken from the center of the disc to the center of the hole. We will use this segment as the hypotenuse of the right triangle.
On the other hand we have the angle alpha formed between two holes. The bisector of this angle (line that divides it into two equal parts) will define the contiguous leg of the right triangle and will form an angle with the hypotenuse of alpha / 2.
And finally, we see that the distance between the centers of the adjacent holes d is also divided by two by the bisector, so there we will have the opposite leg that we needed to complete our right triangle and its length will be d / 2.

With these data and knowing that, in a right triangle, the sine of the non-right angle is equal to the opposite leg divided by the hypotenuse, we can perform the calculations shown:

sin ( angle / 2 ) = ( distance-centers / 2) / radius.

radius = (distance-centers / 2) / sin ( angle / 2 ) .

diameter = 2 · radius .

diameter = 2 · radius = 2 · (distance-centres / 2) / sin ( angle / 2 ) = distance-centres / sin ( angle / 2 ).

If we assume that the measurement taken between centers has been 55 mm. we can substitute "distance-centers" for that measure:

Diameter (BCD) = 55 / sin (36º) = 55 / 0.5878 = 93.57 approx. 94.

The quick formula that we saw previously (56 x distance-centers / 32.9 ) is based on a proportional relationship derived from the smallest anchor sizes that are usually found in bicycle chainrings, which are those corresponding to BCD 56, and with distance between adjacent holes of 32.9, but if you look at the quotient 32.9 / 56 = 0.5878, which is precisely the sine of 36º.

In the event that there are six holes, the angle between them will be 60º (360º / 6 = 60º) so in our calculations for six holes we will use sin(30º) (60º / 2 = 30º), instead of the of 36º

and the BCD will be obtained from: BCD = distance-centers / sin(30)