Preserve scanned pixels

agmrb

Hello

Sorry this is probably a basic or stupid question!

Is it possible to georeference a scanned map yet preserve the pixels 1:1 when saving as a GeoTIFF? I don't want to change the image, just append the georeferencing information, yet GM always seems to warp it.

I understand the display will change depending on which projection I've chosen but I can't think of a way of specifying unprojected if you know what I mean.

(For comparison, MemoryMap works as I describe)

global_mapper

If you are providing control points to geo-reference it there pretty much has to be a warp unless your control points just define a 1:1 linear mapping with just two control points. If you change the resampling method on the Options menu of the rectification dialog to not use interpolation you shouldn't get any color blending, but I'm not sure how you would warp to your control points but not change the pixels at all in a general case.

Thanks,

Mike
Global Mapper Support
gmsupport@bluemarblegeo.com
http://www.bluemarblegeo.com

agmrb

Is it not possible to display the pixels without warping and use the calculated polynomial to show cursor position or when overlaying other images?

global_mapper

That would be kind of like defining a reverse projection where the original stays linear and the warp is defined by the projection and not transforming the image to fit the projection that you rectified in. Typically if your control points are specified in the native projection of the image when it was created and you are displaying it in that projection there wouldn't be any noticeable warp. It is only when the control points define a significant non-linear transformation or you are reprojecting that you would notice the warp.

Thanks,

Mike
Global Mapper Support
gmsupport@bluemarblegeo.com
http://www.bluemarblegeo.com