engleski

Determining Areas from Maps

Today, when most spatial data is in digital form, polygon areas can be determined from maps made in any map projection because the digital format allows projection distortions to be eliminated during measurement. When determining areas from Google Maps and Google Earth, distortion-free values are obtained. Some GIS software (e.g. QGIS, ArcGIS online, Global Mapper) give areas on the ellipsoid as a result of the measurement. In addition, QGIS enables area calculation in the map projection of the map without considering the projection distortion. CAD software (e.g. AutoCAD Map) and cartographic software (e.g. OCAD) as a result of the measurement give the area in the map projection without taking into account distortions caused by the projection. In each of the specified software, the area of Greenland is determined on a map downloaded from OpenStreetMap in the Web- Mercator projection. If the area is calculated in the map projection in which the map was made, even if it is an equivalent projection, the sides of the boundary polygon must be short enough so that the geodetic line can be considered as mapped as a straightline segment. In addition, projection distortions should also be considered.

map, area determination, map projections, Google Maps, Google Earth, QGIS, ArcGIS online, Global Mapper, AutoCAD Map, OCAD

nije evidentirano