I have satellite image files with metadata generated from ArcGIS:

Raster Download Information

Coordinate system ID WGS84:  4326
Top edge WGS84:  35.0003681085064 Degree
Bottom edge WGS84:  34.991149768818 Degree
Left edge WGS84:  -80.4943741887217 Degree
Right edge WGS84:  -80.4841387811576 Degree

I want to map this back to Google map's lat and longtitude, so that I can have overlay of street on the image. I used topedge for lat and left edge for long, but get a different place. How can I find the transformation?

  • 3
    These metadata items are generated from the coordinate system the raster is actually in, in ArcCatalog go to the raster, right click and select properties then scroll down to where you see 'spatial reference', what value is there? According to stackoverflow.com/questions/1676940/… Google Maps is Spherical Mercator in WGS84 (docs.openlayers.org/library/spherical_mercator.html), you may need to project your raster to this. What coordinate system are your roads in? – Michael Stimson Mar 18 '15 at 22:20
  • The spatial reference is Geodetic Reference System 80. I haven't been able to figure out yet, what would be the Google map lat and long of the top left point? – Dzung Nguyen Mar 18 '15 at 23:08
  • 1
    Like spatialreference.org/ref/sr-org/grs80-korea-tm? There is a transformation from GRS80 to WGS84, which according to uvm.edu/giv/resources/WGS84_NAD83.pdf are identical. You will need to project the raster and select the transform model (should be like 0,0,0,0,0,0,0) or ArcGis will not do it properly - even though it's essentially identical. Your units, are they in DD, feet or metres? Is there an WKID: code? (look in the bottom box of the spatial reference), that would help A LOT. – Michael Stimson Mar 18 '15 at 23:28

@Michael is guiding you to the right directions. To extend his answer, The coordinate system of online maps such as Google Maps are Web Mercator.

ArcGIS fully supports this coordinate system. Exact name in ArcGIS is: "WGS 1984 Web Mercator (Auxiliary Sphere)"

To convert from WGS84 to this coordniate system, there is valid transformation in ArcGIS for Desktop:

WGS84 to WebMercator Conversion

The math behide the conversion is already answered here: Converting geographic WGS 84 to Web Mercator 102100


Base on comments, if the question asker wants to transform from GRS 1980 to WGS80, then a datum conversion must be applied, first. List of valid datum transformation are availabe from this knowledge base (datum) transformation when projecting between datums

  • That's a good answer except that the input data is not in WGS84 - that would be too easy. The only difference should be the geographic transformation (optional) perhaps should be filled out with GRS80 to WGS84 transformation, when I emulated the spatial reference ITRF_2000_TM_Korea_Central_Belt and projected to WGS84 it worked fine without it... So perhaps it's just GDA94/WGS84 that needs a 7 by 0 transformation. – Michael Stimson Mar 19 '15 at 2:40
  • If it is not WGS84, then the question should be edited, because I can see this line "Coordinate system ID WGS84: 4326". – Farid Cheraghi Mar 19 '15 at 3:07
  • maybe IGRS_To_WGS_1984_1 is a good fit here! downloads2.esri.com/support/TechArticles/… – Farid Cheraghi Mar 19 '15 at 3:15
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    That's from the metadata, the part where it converts the extent into WGS84 coordinates for easy indexing by a Metadata Service... at some point somebody had a good idea that everything should be rendered to WGS84 for indexing purposes... to save the metadata service having to convert every time it skims over the data, that definitely does not mean the data is in WGS84. – Michael Stimson Mar 19 '15 at 3:46

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