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Shapefile offset when overlaying a shapefile in WorldWind/Google

Topics: General Topics
Mar 9, 2009 at 6:10 PM
I am using SharpMap to read a shapefile and then display this shapefile as a layer in WorldWind. The shapefile is unprojected, and has no specified datum. I am using a common "countries.shp" shapefile showing countries of the world. When I load this into WorldWind I am seeing a easterly shift of about 15-20 km in the shapefile boundaries compared to the WorldWind map. I have tried converting the datum to wgs84 but I am not sure of the datum of the shapefile. I have converted the shapefile to KML and I see the same offset in Google Earth. It seems that I am not taking into account some datum/conversion but I do not know which conversion I should be applying. I have used MapWindow to convert the datum of the shapefile but have not figured out what is causing the offset. Any help would be greatly appreciated. Thanks.
May 13, 2009 at 9:00 PM

I'm having a similar problem. Did you find a solution?

May 15, 2009 at 4:59 AM

No. I had this problem with this one particular shapefile. This shapefile loads with an offset in WorldWind(with sharpmap) and it shows the same offset in Google Earth after converting to KML. I also loaded this same shapefile into Arcmap and it again shows the exact same offset.

I had no luck fixing the offset by converting to WGS84. The offset seems too large, and in the wrong direction to be NAD27, but I tried converting to WGS84 anyway.

All of the other shapefiles I have load correctly. In fact I have a similar shapefile to the "bad" shapefile that loads fine. Our customers gave us this shapefile and it exists on the internet. I do not know how it got created.

Since this is the only file I had a problem with, and since Arcmap loads the shapefile exactly the same as I do, I quit looking at trying to see what the exact problem is.

----- Original Message -----
From: BradMartin
To: [email removed]
Subject: Re: Shapefile offset when overlaying a shapefile in WorldWind/Google [SharpMap:49634]
Date: 13 May 2009 13:00:50 -0700

From: BradMartin

I'm having a similar problem. Did you find a solution?

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