3

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

  • 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. – user3461 Nov 10 '12 at 11:21
  • 1
    If you don't get an answer here, you may want to ask at 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 1 '12 at 11:33
  • Can you check the geometry and at least see if it is likely projected(meters or something) or geographic(degrees)? – user10353 Dec 31 '12 at 15:46
3

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

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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