re-projecting .tif's

[dstapp]

I am using MAP2005 and have inserted images of USGS topos in UTM NAD27. When I query the image corners I get Lat/Longs that match the data printed on the map. However, when I use map to query it into UTM NAD83 and query the the same points, they are slightly off by 200'-600'. Is this correct and am I wrong to expect the Lat/Longs at the image corners to read correctly after they have been re-projected?

Thanks,

[jim.dahl]

It sounds like you know what you are doing. I have done this about 5 years ago and did not have time to test it now. But if you have the image correct in a defined source DWG of NAD 27 and query into defined DWG of NAD 83, it should be OK. Depends on what part of country you are from, but up in Minnesota and ND the shift was several hundred feet between 27 and 83, mostly in North-South direction. If need more help please let us know.

Just curious on your source of the DRG and if it really had a world file for NAD 27 (or georef if a GEOTIFF).


Jim

[dstapp]

Thanks Jim - I think I sorted this out. I am confidant the reprojected DRG's are ok now that I found some with NAD83 ticks to verify. I purchased the files on line from MapMart and I'm pretty sure they have world file's and are not GEOTIFF's.