TransDEM Forum

Roland (or anybody who would like to),

Could you please check these historical topo maps in TransDEM 2.4?

Here are 3 geoPDFs of a topo called "Harrisburg West" from central Pennsylvania. They are historical topos from 1947.

http://ims.er.usgs.gov/gda_services/dow ... id=5931237
http://ims.er.usgs.gov/gda_services/dow ... id=5953037
http://ims.er.usgs.gov/gda_services/dow ... id=5324410

They seem to load OK in TransDEM 2.4 and I can get the Transparent Margins highlighted OK:



But when I go to Convert to UTM, the results aren't as expected:



Either I'm doing something wrong, or these topo maps are defective. The 1943 "New Cumberland" topo map just south of this one loads and converts just fine. I thought maybe it was right on the edge of the UTM zone, but it is still a map or two to the west.

Thanks for your assistance.

Andrew

G'day Sharknose,

Andrew, I believe there may be a problem with the files. Following the instructions, I obtained the identical results to you. However, after a applying a little "thinking outside the box", I was able to obtain the following result, by manually cropping the image (using the Transparent Margin as a guide)...




...but if you look carefully, you will see that TransDEM has 'automatically' geo-referenced the file with the Equator (0°N, right at the very bottom of the map) somewhere around the middle (or southern outskirts) of Harrisburg, which is not how I remember it being the "last time I was there"...

Jerker {:)}

Thanks for the confirmation, Jerker! I kind of figured that the 3 files were goofy in some way. When I am ready to use these, I guess I'll have to do a manual georeferencing on them.

Yes, there is an error in the map meta data. You can correct it yourself.

Proceed to the step where TransDEM displays the map, but do not convert to UTM.

Now go to the TransDEM temp folder which is usually located at C:\Users\<your user name>\AppData\Local\TransDEM\temp
(You may need to activate the "Show hidden files an folders" option in Windows Explorer.)

Use a text editor to open and edit PA_Harrisburg West_461755_1947_24000_geo.png.aux.xml (for the first file in the series).
Find and replace with Save.

In TransDEM, open C:\Users\<your user name>\AppData\Local\TransDEM\temp\PA_Harrisburg West_461755_1947_24000_geo.png and proceed normally including conversion to UTM.

That's got it! Thanks, geophil! I'll print this set of instructions out...

Just an FYI:

Nine of the 1947 Historical PDFs in and around Patchogue, Long Island, New York also have the above problem. They can also be fixed using the above method.

Edit: Must be a 1947 thing...

Andrew