Mosaicing ortho photos

[MattWeldy]

I downloaded some .img ortho photos off the national map viewer. The images are displaying well as individual tiles; however, for workability I would like to mosaic them.

I converted the .img files to grid and then in catalog load>load data  I used the mosaic tool. and keep getting this error
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Error 999999 error executing function

Failed to open raster dataset

Failed to execute mosaic
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I am new to this please tell me what I'm doing wrong.


Thanks,
Matt

Thanks

[JeffreySwain]

Depends on your 'conversion' step, if you wanted to put them all together, you could have simply used the mosaic to new raster or depending on your version of ArcMap use a Mosaic Dataset.  If the 'conversion' did not involve the Copy Raster tool or export, then you might have invalidated the rasters in the process.  If you want more specific help, then  I recommend contacting Esri Support.

[EricRice]

Just adding to Jeff's response.  There is no need to convert .img to GRID before running mosaic.  You can mosaic the .img's directly. 

Best,
Eric