Google maps measure distance1/7/2024 The farther away from the Equator you get, the more distorted your measurements will be. In cylindrical projections like this, errors are minimized along the standard parallel(s), and in the case of the Mercator projection, this standard parallel is at the Equator. If you perform measurements in the Mercator projection or the Google/Bing/ArcGIS Online variation thereof, your results will likely be much larger than you intended. This is evident from the enormous dimensions of Greenland and Antarctica relative to land masses closer to the Equator: The projection sacrifices some accuracy because it is based on a perfect sphere (the earth is better approximated by a spheroid), but the biggest problem is the heavy vertical and horizontal stretching at extreme latitudes. This projection fit the entire globe (well, most of the latitudes anyway) into a square area that could be covered by 256 x 256 pixel tiles. Instead, it was engineered for convenience in working with cached map tiles. The modified Mercator projection used by Google, Bing, and ArcGIS Online is not designed to minimize distortion at all. Other projections (such as UTM and State Plane) are designed for focused areas of the globe in order to keep the distortion minimal. Some projections such as Robinson or Winkel Tripel attempt to minimize distortion across the world through some compromise of all those factors. Why is the Google/Bing/ArcGIS Online projection not acceptable for measurements?Įvery map projection causes distortion of shapes, areas, directions, and/or distances. You should instead re-project user-submitted geometries into a more appropriate coordinate system before you perform a measurement. If you use the new ArcGIS Online services, avoid the temptation to perform measurements of polylines and polygons in Web Mercator. Recently, ArcGIS Online services became available in the same “Web Mercator” projection used by Google Maps and Bing Maps.
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