Tell me more ×
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It's 100% free, no registration required.
up vote 2 down vote favorite

I have saved Google Maps image (not Google Earth) of area at latlon(17.692437,83.218689) by some method in jpeg format. It is an exact snapshot of the Google Maps. Now I need to geo-reference it to use it as base map for my digitization. What projection or coordinate system shall I use? Some says its WGS-84 Mercator projection. But I see no Mercator projection in GCS list in ArcGIS. Please help! I am confused.

I want to georeference it by assigning exact latlon values to the points as in google maps.

Extend : Now I got another question. Is Google Maps in Projected Coordinate system or Geographic Coordinate system. Though it displays LatLon values, I think it is projected coordinate system. Am I right?

Extend

I set the projection of ArcMap Dataframe to Projected Coordinate System ( Web Mercator) and changed the display values from Meters to Decimal Degrees. Then I added the Google Map with no geo-referenced data to dataframe. Then I took some common control points in my ArcMap image and Google Maps, set the Latitude and Longitude values from Google Maps in ArcMap image points, After assigning latlon values to 4 points, I click on update georeferencing. Then my image is transformed very strange. Is the procedure I did correct?

share|improve this question
2  
Are you sure what you are doing is legal? Google's TOS may prohibit this. See question 8 on this page: google.com/permissions/geoguidelines.html – blah238 Feb 18 at 17:41

1 Answer

up vote 2 down vote

Google uses WGS 84 Web Mercator as its coordinate system. In ESRI it is under geographic coordinate systems.

share|improve this answer
But Web Mercator is Projected Coordinate system? – Jeevan Patnaik Feb 18 at 16:37
1  
Yes, it is projected, with their own method ;-). They display lat/lon coordinates, but a map in lat/lon would look rather distorted if you come north. If you zoom to world extent, you see that Greenland is much too big. Thats typical Web Mercator. – Andre Joost Feb 18 at 18:03
1  
Internally Google Maps is using a projected coordinate system (spherical Mercator), but when you query for or pass in coordinates, the API returns lat/lon. – mkennedy Feb 19 at 17:09

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.