====== Map 3D Measurements ======


The main toolbar Measure function can be used for measuring positions, distances, polylines, areas and volumes inside  the Orbit [[111:orbitgis:map:index|MapCanvas]]. \\ 
The measure results are expressed in the units used by the [[111:technologies:crs:crs_orbit#Mapcanvas CRS|MapCanvas Coordinate system]]. 

<note>The functions to measure on the Map 3D are similar to the functions to [[111:mobile_mapping:desktop:core:use:measure|]]. We will update the documentation on measuring inside the Map 3D very soon.</note>


===== Different measure results depending the used CRS =====

A measurement in metric units is always calculated in an projected Coordinate Reference System. Consequently you will have a different result for the same object measurement in different Coordinate System. The measurement depends of the properties of the projection in the measure area.
\\ \\
For example the Mercator projection conserves the angels, not the distances between different points. The distance increases closer to the poles. Have a look at the size of Greenland for example. It is about the same size as Saudi Arabia, about 2 million square kilometres.
\\ \\
{{:orbitgis:mapcanvas:selection:crs_mercator.png?nolink}}\\
(c) Source image : http://www.heliheyn.de/Maps/GallPeters/GallPeters_E.html
\\ \\
Read more about the Coordinate reference systems and the supported systems here :
  * [[111:technologies:crs:crs_orbit|]]
  * [[111:technologies:crs:crs_theory|]]