TransDEM Forum

I recommend 1:30000. With the scale factor left at the default of 10000 you won't lose any detail. The nominal scale is 1:24000. However, those maps were scanned with more dpi than necessary and we can save on memory by reducing resolution a bit.

I understand.

I used this because it gave me a very resolute map, probably a random choice selected on a "hit or miss" basis. I went to a 5% overlap and use horizontal and vertical poly lines to reduce the amount of files.

And yes, I watch Task Manager because it requires a metric-ton of memory...I'll try this your way.

Yet another source for USGS DRG topo maps 1:24k:

http://libremap.org/

They come as (ordinary) .tif files, but with a world file accompanying each image. TransDEM (2.2 required) will read and process the world file.

A few futile attempts to connect to the USA_MS_Research_Maps (Terra Server) site induced some sleuthing. A "Yahoo!" search of "Microsoft Research Maps" yielded "Web Site Shutting Down May 1, 2012. Microsoft Research Maps web site will permanently close on May 1, 2012." Attempts for more information from the URL: "msrmaps.com/About.aspx?n=AboutShutdown" yielded a spinning wheel on an empty browser page. They were not kidding!

It is now necessary to pay closer attention to procedures for the alternates like libremap and the USGS material. For now, some studying is in order, but be prepared for a barrage of questions about set-up for the other servers to get the same nice string of maps previously available from MS_Research_Maps.

George

The USGS gives the opportunity to download 7.5 minute quadrangle maps. These are georeferenced. However, because they are in *.pdf format, I do not think they are directly usable in TransDEM. There is, however, a work around using screen capture, editing in Windows Paint and then georeferencing in TransDEM.

Preparation of areas for screen capture employs an application the USGS website offers on its map download page. There, TerraGo Technologies offers "TerraGo GeoPDF" as a free download. One of the utilities in the application, GeoTracker, allows placement of a mark on the PDF map. It opens a small window giving coordinates of the mark. The user can choose from a large number of referencing systems, including UTM/WGS84 by zone for the coordinates.

Screen capture of the area, including the mark and the coordinates display window generates a bitmap. Repetition three more times around the rectangular area of interest generates three more bitmaps that can be merged into a single bitmap in Windows Paint or other similar program. Naturally, for best results, it is important the screen capture bitmaps overlap, (but not so the overlap covers the coordinate information).

With careful manipulation, the resulting raster map will have four marks near its corners with the WGS 84/UTM coordinates for each in a window nearby. Opening the raster map in TransDEM enables conversion to a georeferenced raster map that works with others.

This is quite a lot of work, but is one way to make this resource usable. Are there others? I apologize if I have repeated something on the board or made favorable reference to Dr. Ziegler's competition!

The USGS National Map WMS, launched a year to two ago, apparently has undergone some heavy overhaul. It's much easier to use now. The number of layers has been reduced dramatically and you no longer have to determine the UTM zone beforehand. It's now as simple as MS Research Maps / Terra Server used to be.

What it also seems to support is automatic zone transformation. I tried with the California coast and access zone 11 data from zone 10 and it just worked. That's now definitely ahead of MRM/TerraServer and a large step forward for the USGS National Map WMS.

G'day geophil,

Roland, your mention of the USGS, here, has prompted me to ask (although, perhaps, I should do so more properly in the 'Future Requests' thread), if it would be at all possible to 'tap' into the WMS function that I know the original web site offered and which might still be available for the data from this new source, thereby 'allowing' us to obtain DEM data (at the desired resolution) in a similar manner to the way we can now obtain high resolution topographic data (from MSRMaps, of course) using the route polyline method? This would 'revolutionise' (and streamline) the DEM data acquisition process considerably...

Jerker {:)}

Garry, do they actually offer raw DEM data via WMS? I have seen a few providers who have pseudo-DEM layers, often as a coloured shaded relief. While those images are based on the DEM, it would be very difficult to extract the raw data from the processed image. GeoTIFF is more or less the only suitable format for raw DEM data as raster image.

It would also require quite a bit of effort in TransDEM, since the work-flow for DEMs and raster maps is quite different at the moment.

G'day geophil,

I could not really say how the data was 'offered' - I merely noted that it was available and hadn't delved into the 'nuts and bolts' of the matter too deeply. However, when I tried to confirm my recollections (by opening the original site), my 'old' URL redirected me to the 'new' site, where, unfortunately, I could not find any reference whatsoever for WMS...

Jerker {:)}

Edit Dec 22, 2012: Outdated. See here instead.

Now, with the USGS Seamless Viewer retired, we have to cope with the National Map Viewer. It's different, but - in my humble opinion - not really more user friendly than before.

After starting the viewer, focus on the map window, don't bother with the overlay data layers on the left. You won't find "elevation" or "DEM" in there. Zoom in to the area of interest and click "Download Data". In the "Download options" pop-up, use "Click here" to download by current map extent. A new dialog pops up, presenting you an "Elevation" option for the first time. Select it and leave the format at the default "GeoTIFF". Click "Next".

That next dialog will show you the available products. You should find 1 arc sec and 1/3 arc sec. I recommend the "dynamic" type as that will indeed download by map extent. Select 1 or 1/3 arc sec (or 1/9 if available). Click "Next". Your selection will appear in the main window in the side bar on the left. Inspect your selection and click "Checkout". You will now have to enter your email address as you will get the download link by mail. I guess that's to keep demand and traffic down, but it's a cumbersome process. Click "Place order" (no charges). Unfortunately you get no information on the data size and the number of files at this time.

Check your email inbox. You should receive message from USGS.gov shortly with one of more links in it. Click the the link(s) (depending on your email/browser software). A new window will open in your browser. It's only now that your order will be processed. Once that is complete, your download finally becomes available. (These last steps are very similar to the Seamless Viewer procedure.)