# Additional information, curiosities and glossary of terms

## GPS (Global Positioning System) and others global positioning systems

Global positioning systems are systems that allow locating an object on Earth with high precision.

More information in this link Global positioning systems

## Geographical 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.

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## Waypoint (point of reference)

It is a specific position of a point on Earth defined by geographical coordinates. It is identified by a name and usually includes an icon or graphic symbol and other additional information such as a comment, date, altitude.

## Notation systems: sexagesimal degrees and decimal degrees

The sexagesimal system is used to express measurements of time and angles using three groups of values: degrees, minutes, and seconds. It is based on the number 60 and is the system traditionally used in paper maps.

Time: 1 h 60 min 60s

Angle: 1º 60’ 60”

In the case of geographical coordinates, for latitude the hemisphere to which they belong is usually indicated, north (N) or south (S), and for longitude, whether they are east (E) or west (W).

Example: 39°49'51.8"N 3°46'49.2"W

North hemisphere: Latitude between 0° and 90 °

South hemisphere: Latitude between 0° and -90°

To east of Greenwich meridian: Longitude between 0° y 180°

To west of Greenwich meridian: Longitude between 0° y -180°

In computer applications, the decimal system is usually used, in which minutes and seconds are transformed into a decimal number.

39°49'51.8"N 3°46'49.2"W = 39.831045, -3.780322

For the manual conversion of sexagesimal degrees to decimal degrees, the sum of:

Degrees + minutes divided by 60 + seconds divided by 3600:

Example:

39°49'51.8"N = 39 + (49/60) + (51.8/3600) = 39.8310

3°46'49.2"W = 3 + (46/60) + (49.2/3600) = 3.7803

To carry out the conversion there are multiple applications and calculators on the internet.

## Unevenness and slopes

The unevenness, 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.

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## 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.

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## Basic notions on map interpretation

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).

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## Magnetic declination

The magnetic field generated by the Earth is not immutable, on the contrary, it constantly varies both in its position and in its intensity and also periodically (in cycles of thousands of years) it is reversed. Currently, he travels about 100 meters a day. Since a compass will always indicate the magnetic north pole, it is convenient to know the relationship or difference between the north indicated by the compass and the true or geographic north. This concept is magnetic declination. Magnetic declination (“variation” in aeronautical navigation) is the angle between true (geographic) north and magnetic north, that is, it is the difference angle between geographic north and the north that a compass will mark.

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## Navigation concepts. course and heading

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.

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## Types of maps

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

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## Cartographic 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.

More information in this link Proyecciones cartográficas

Clouds

Clouds can give us valuable information, we are going to review the different types of clouds that we can find on our outings.

More information in this link Cloud types

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