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#1
Hans van der Maarel

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I'm trying to figure out the coordinate system used by Mapquest tilesets, but I'm having a bit of a hard time...

It's documented as:
"The type of projection used for the custom tile layers is the Lambert Equirectangular projection with a standard parallel of 37.5 degrees and a spherical earth (km= 6378.160187 & mi=3963.205). The closest known Datum that lines things up on our actual output is Australia 1984."

Unfortunately there's only 4 references to "Lambert Equirectangular" found in Google (the first one being me asking this question on the Global Mapper forum, #2 and #3 coming from the Mapquest documentation PDF which I quoted above). I think, but I'm not even sure, they're referring to the Lambert Cylindrical Equal Area projection, using WGS4_Spherical as a datum, or simply unprojected lat/lon (which is sometimes referred to as equirectangular).

Any help would be highly appreciated.
Hans van der Maarel - Cartotalk Editor
Red Geographics
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#2
christine.skl

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I'm trying to figure out the coordinate system used by Mapquest tilesets, but I'm having a bit of a hard time...

It's documented as:
"The type of projection used for the custom tile layers is the Lambert Equirectangular projection with a standard parallel of 37.5 degrees and a spherical earth (km= 6378.160187 & mi=3963.205). The closest known Datum that lines things up on our actual output is Australia 1984."

Unfortunately there's only 4 references to "Lambert Equirectangular" found in Google (the first one being me asking this question on the Global Mapper forum, #2 and #3 coming from the Mapquest documentation PDF which I quoted above). I think, but I'm not even sure, they're referring to the Lambert Cylindrical Equal Area projection, using WGS4_Spherical as a datum, or simply unprojected lat/lon (which is sometimes referred to as equirectangular).

Any help would be highly appreciated.



The only other reference I found to your question is confirming your suggestions. I don't know how much this would help, but here's the link:


http://www.ga.gov.au...-projection.jsp

And the quote:
"Equirectangular projection
Otherwise known as geodetic, geographic, rectangular, plate carre or unprojected map, the equirectangular projection can be used with any of the available datums, AGD66, GDA94 or WGS84."

If this gives any suggestions I am glad.
Christine

#3
Hans van der Maarel

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If this gives any suggestions I am glad.


Well... it does seem to confirm my suspicion.

Then again... the docs do mention a standard parallel. And unprojected lat/lon doesn't have standard parallels...
Hans van der Maarel - Cartotalk Editor
Red Geographics
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