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How do I use the seamless server?


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#1 ctempire

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Posted 29 January 2010 - 08:21 PM

Hello. I'm curious about seamless.usgs.gov. How do I get the best dem available for free? I'm tired of using the 1:25000 dem available.

#2 Hack

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Posted 29 January 2010 - 10:53 PM

There might be a tutorial on this on Steam4Me, but it appears to be down atm. I believe most of the info you seek can be found on the USGS site, however.

Cheers!
Marc

#3 old_codger

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Posted 30 January 2010 - 06:16 AM

In the mean time. this link may help.

http://forums.uktrai...b13392#p1167740

#4 charlie

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Posted 30 January 2010 - 06:57 AM

How do I get the best dem available for free? I'm tired of using the 1:25000 dem available.

This is a procedure that I originally wrote for the UKTrainSim folks who came to DEMEX late (see "old codger's" link above). Edited to fit the USA...

1) If you have not registered DEMEX

Before you start, in the RGE, using cursor position, identify the Lat/Long extents of the download that you wish to have. Add a tenth of a degree or two all around if you're uncertain.

If you use this procedure, you don't even have to wait for the map to load. From here, http://seamless.usgs.gov/index.php, just click on the United States Data area and proceed as follows. This seems to always work, no zooming required or waiting for the map.

At the Seamless page, on the right side under "Layer Extent", For the USA select the Elevation that you want (as in NED 1/3 arc sec for 10 meter resolution or NED 1 arc sec for 30 m). You'll see a colored overlay of the DEM coverage.

On the left side under "Downloads", select the middle button on the top row for a download by Lat/Long coordinates. This will let you enter your Lat/Long coordinates directly. When the new window pops up, click on "Switch to decimal degrees", and then enter your Lat/Long coordinates.

At the "Request Summary Page", click on "Modify Data Request" and scroll down to make sure that the set you selected is ticked (either National Elevation Dataset (NED) 1 Arc Second or National Elevation Dataset (NED) 1/3 Arc Second).

Change the data format to GeoTIFF.

Scroll down to save changes and return to the Summary Page. Press the Download button. Unzip the archive, select the route in DEMEX, then point DEMEX to the *.tif file. That's it...


2) If you have registered DEMEX

Install the Open Beta "demexbeta02.zip" for DEMEX from, http://www.digital-rails.com/files/.

At "Route" on the menu bar, choose "Select route...". After the quad tree is displayed, at "DEM Management" on the menu bar, choose "Seamless NED 1 sec " or "Seamless NED 1/3 sec" (for the USA).

At "DEM Management" on the menu bar, choose "Retrieve DEMs", and you will bypass the USGS site "front end" and directly have the "Request Summary Page". This download is exactly tailored to the needs of your quad tree.

With registered Demex, here's what really happens for std tiles after you've selected "Seamless NED 1/3 sec" (10m) and then "Retrieve DEMs". You almost instantly get a pop-up USGS download page that's the start of a simple jigsaw puzzle that has rectangular parts. Depending on the shape of your quadtree, there may be one or more downloads on the first USGS page.

At the same time, a little pop-up window appears in Demex. I never press OK on that pop-up until I have safely obtained the downloads from first USGS page. When you do press OK, you'll get the next USGS download page. Continue this repetitive process until Demex tells you that you have all of the DEM's.

You're not forced to use the download folder path that Demex suggests in the little pop-up window. Since the GeoTiff file names are an 8 digit numerical and you can't tell where in the Universe they fit from the number alone, I use a sub-folder under NED10 (or NED 30 for DM's) that is named for the route. Once all of the zips are collected, unzip then so that Demex can get at the *.tif files. I always tick Delete Buffers, Fill Seams and Retain Data first. In Demex, navigate to your download folder and begin. At the File menu use Open DEM... for the first, then Merge Dem... to assemble the rest. Remainder of the procedure is as above.

Pretty simple...

As a side note, the DEMEX Beta can take over the former duties of the RGE in terms of adding or deleting tiles in the quad tree. You actually need only one standard tile present that was generated by the RGE to get started. DEMEX can do everything else, including the distant mountains quad tree.

regards,
charlie

#5 FSSARNO

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Posted 12 October 2011 - 02:14 PM

Hello Charlie! I use your above item to do my distance mountains,but have a problem with this time after time i download all files for my route Alaska_RR from usgs Geotiff and i install this in demex,always there is part missing in the route,what i'm doing wrong. i follow the notes from your forum. I even tried to use this with a download from a specific location-lat and lond still there is same part missing or failed to get any DM to this area,what is wrong??? I know my english is not very good. Please help. Thanks Charlie! fssarno Arno

#6 charlie

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Posted 13 October 2011 - 06:23 AM

....for my route Alaska_RR....in demex,always there is part missing in the route,what i'm doing wrong.

Hi Arno,

For Alaska you must be careful to modify the data request to match the type of DEM for which there is coverage. If you are trying NED Shaded Relief (1/3 arc second) or NED Shaded Relief (1 arc second), you are probably out of luck for most places.

However the Seamless Viewer shows complete Alaska coverage with NED Shaded Relief (2 arc second) DEM's. I don't know what else to suggest.

EDIT: Another thought occurs. If you are asking DEMEX to go get the DEM's, you routinely get several download pop-ups in a sequence to complete the pieces needed to fit your route's quadtree. Any of the pop-ups can have more then one download link in it. Make sure you leave such pop-ups open until you have all of it before you close it and go on to the next...

Charlie

#7 FSSARNO

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Posted 13 October 2011 - 03:17 PM

Hi Arno,

For Alaska you must be careful to modify the data request to match the type of DEM for which there is coverage. If you are trying NED Shaded Relief (1/3 arc second) or NED Shaded Relief (1 arc second), you are probably out of luck for most places.

However the Seamless Viewer shows complete Alaska coverage with NED Shaded Relief (2 arc second) DEM's. I don't know what else to suggest.

EDIT: Another thought occurs. If you are asking DEMEX to go get the DEM's, you routinely get several download pop-ups in a sequence to complete the pieces needed to fit your route's quadtree. Any of the pop-ups can have more then one download link in it. Make sure you leave such pop-ups open until you have all of it before you close it and go on to the next...

Charlie

Thanks Charlie!

fssarno
arno