Mosaic has no projection data

[jdstark]

I'm trying to mosaic several NAIP compressed county mosaics (.sid format) and clip them using an ESRI shapefile containing a single polygon. All of the mosaics as well as the clip file are in the same projection (UTM Zone 18, NAD83). The resulting mosaic looks OK, and the clipping function seems to work.

The problem is that the mosaic has no projection information. When I check properties in ArcMap, it says the projection is not defined. When I display it in ArcMap with other data, it shows up somewhere near the north pole, even though it's supposed to be near Philadelphia. The source mosaics all have world files and .aux files, and the shapefile has a valid .prj file.

I tried running it with the Reproject option, putting in the same projection for input and output, but I get an error saying that the clip file has no projection. And I couldn't find any place to enter a projection for the clip file.

Any suggestions?

[rparker]

In GeoExpress 7.0.3 you can take your mosaic and add it to the "Edit Metadata" tab. There you can add a coordinate reference system to the image without reencoding it.

[jdstark]

Thanks. That worked, though one would think that if all the inputs had valid projection data, Geoexpress should be able to read them and transfer them to the output file...

I am trying to automate this process in a Python script. What is the equivalent command line? There is a "-towkt" switch for the mrsidgeoencoder command, but the command line user's manual has it listed under reprojection switches. In this situation nothing needs to be reprojected. If I use the "-fromwkt" and the "-towkt" switches, both referring to the same ESRI .prj file, will they cancel out the reprojection process and just add the data?

I just want to add projection data to the file, and everything I've read about the mrsidgeometa command is vague, suggesting that it can be done, but not actually showing how to do it.

[rparker]

It's possible that the projection information is stored in an aux file which we do not read (instead of the metadata of the image).

The command line documentation for mrsidgeometa is available here:

C:\Program Files\LizardTech\GeoExpress 7\docs\Command Line\index.html

It contains specific examples to help get you started.