[Xastir] Starting with a scanned USGS 7.5" paper map....

[Jim Tolbert]

I am collecting the USGS topographic maps for  my area and I am 
fortunate in that all except one were on Libre Map.  The one that was 
missing, The good folks at UW Madison Geography Library had the paper 
map and scanned it for me.  So now I have a 454MB scanned image in tif 
format.

Setting aside the fact that for one map, I would probably be better off 
just buying the proper Geotiff map files............  How do I go from 
this scanned image to a georeferenced digital file?  Can I get there 
from here?

Looking at the other fdg files in the set, it seems that they indicate 
that the USGS 7.5" maps are reduced to 250dpi.  When I do that, my files 
are ~3X the other geotif files in the set (10MB vs 3.7 MB). 

Using GeoTiffExaminer  
(http://www.mentorsoftwareinc.com/FREEBIE/FREE0699.HTM ), it would seem 
that I could convert a scanned tif image into a Geotiff file if I knew 
what georeferencing info to give it.

In trying to understand README.MAPS, it seems that those instructions 
assume that you are starting with a GeoTiff map of some extraction.

Many thanx............. jt

-- 
Jim Tolbert
RiverRidge Consulting, LLC
PO Box 536
Webster, WI 54893

715-866-4398 home office
715-349-8993 fax

RiverRidge at CenturyTel.net