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 Post subject: Polymask problem
PostPosted: 13 Aug 2021 03:48 
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Joined: 10 May 2011 04:39
Posts: 26
I am trying to prepare a historic raster map using the Polymask tool. I first did Reduce Image, next cropped the edges, next used the polygon mask tool to pick the edges of the map. When I click the polygon tool again I do not get a message box asking for
confirmation to apply transparency? Also the raster map I'm using is not tilted.

Dave


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 Post subject: Re: Polymask problem
PostPosted: 13 Aug 2021 18:29 
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Joined: 05 Jan 2011 16:45
Posts: 1463
Quote:
When I click the polygon tool again I do not get a message box asking for
confirmation to apply transparency?
I think it's automatic. Once you have completed the georefencing points and click "Convert to UTM", the polygon mask will be applied during the conversion.

(With a USGS GeoPDF source, where TransDEM recognizes the projection, you don't enter georeferencing points, of course, and go straight to "Convert to UTM" after clicking the polygon mask tool the second time - and the margin has become semi-transparent.)

The behavior may been slightly different in earlier versions of TransDEM, but I am not sure.


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 Post subject: Re: Polymask problem
PostPosted: 13 Aug 2021 18:50 
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Joined: 10 May 2011 04:39
Posts: 26
OK from the USGS should I use GeoTiff or GeoPDF?


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 Post subject: Re: Polymask problem
PostPosted: 13 Aug 2021 19:29 
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Joined: 05 Jan 2011 16:45
Posts: 1463
You have to try, I'd go for GeoPDF first. For several years it was the only option for raster maps anyway. The GeoPDF format has the advantage that it can incorporate the so-called "neat lines" which then become the pre-set for the TransDEM margin mask. I don't think GeoTIFF can do that. But GeoPDF is slower to read, because it's two-pass procedure.


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