Saturday, July 28, 2007

More on what projections and datums are used in Google Earth and Virtual Earth

For all the discussions about the map projections used in these online mapping systems, I hadn't found any documentation on the MSDN site or the Google API site. I finally found a few documents on both sites that confirm the fact that they both use the Spherical form of the Mercator projection and that latitude and longitude values are assumed to be in a WGS 84 based datum. Virtual Earth. In this document about the Virtual Earth Tile System, there is a ton of information regarding the projections, datums and calculations used in VE map system. (Latitude and Longitude values are assumed to be in the WGS84 datum.) Google Earth. In A Note About Projections and Datums, the GE team confirm that the spherical mercator projection is used. (which is also called "Lat/Lon WGS84" projection) In What is a Datum?, they confirm that the WGS 84 datum is used. The above information is all collated into the following document "Importing your data into Google Earth"

No comments: