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I have a bunch of maps that are output from a land use model in .asc format, but none have a projection file associated. The person who originally ran the LU model is long gone, so I don't have access to the files that were the original input to the model. I've gone through http://spatialreference.org and ad-hoc tried to fit my data to all the projections that looked remotely worth trying, as suggested here and in links within.

Details: Using ArcInfo 10.0. Data is for China. Gauss-Kruger projections came close to looking correct (after on-the-fly projecting on top of my known reference data), but were still several hundred km off in places and somewhat distorted. I think my only recourse is to manually project these projectionless shapefiles - which really sounds like a non-solution to me. Anyone have thoughts on a better fix?

Here's the extent info Top: 5924000 Left: -2638000 Right: 2210000 Bottom: 1870000

Thanks

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bertastic
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  • I'd try the most common ones:
    • WGS84 - EPSG4326
    • Google Mercator - EPSG900913, EPSG3857

    And I assume it's the 2. one. ;)

     – Styp Nov 10 '12 at 11:05
  • The data sounds fairly old, considering the history and ASC format. I would not assume the projection is Google/Web Mercator, or any related reference such as EPSG:4326. –  Nov 10 '12 at 11:21
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    If you don't get an answer here, you may want to ask at http://lists.maptools.org/mailman/listinfo/proj - a lot of experts are subscribed. I had good success in the past there guessing e.g. WWII coordinate systems. – markusN Dec 01 '12 at 11:33
  • Can you check the geometry and at least see if it is likely projected(meters or something) or geographic(degrees)? –  Dec 31 '12 at 15:46

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I agree with @Kevin, I don't think it would be projected in Google Mercator, as it sounds too old-school, and that's never been considered a serious projection by the science community.

If you know approximately where the data should be in China, I would recommend trying the most-appropriate UTM projection for the given area. If the data straddles a zone boundary, start with the zone that it spills into the most.

This map of UTM zones might be helpful: http://www.dmap.co.uk/utmworld.htm

elrobis
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