TUTORIAL: Downloading DEM / SRTM terrain data

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TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby BoostedFridge » Tue Jan 10, 2017 1:41 am

The National Map viewer website has recently changed the way that you download the DEM/SRTM files which we use to generate real world terrain for Train Simulator routes. The tutorial below covers how to choose the DEM type, confirm availability for your area, and then download these files. After downloading, you can use the excellent tutorials by bnsfsubdivision to prepare, and import the files into Train Simulator.

The URL for the updated mapviewer is: https://viewer.nationalmap.gov/basic/

1) Click on the checkbox for 'Elevation Products'

USGS 1.jpg
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2) Ensure the button for 'Box/Point' is checked, then click a point on the map and drag your cursor to create a green rectangle that covers the entire route that you want to make. In this example I have positioned the rectangle to cover the BNSF rail line from Tacoma to Yakima. You want to make the rectangle slightly larger than the furthest points on the route you are making.

You can adjust the size and position of the rectangle after it is placed also by dragging the white squares on the corners of the rectangle.

USGS 2.jpg
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3) Check the availability for the type/quality of DEM files you wish to use in your route.

- 1 arc-second gridfloat is the highest resolution/quality DEM that you can import to Train Simulator without using the program ReDem. This is what I recommend for beginner and novice route builders, or those just looking to quickly make realistic terrain for their route.

- 1/3 arc-second and 1/9 arc-second IMG or gridfloat types can be imported if you use ReDem. This is a more complicated process, but gives you terrain this is more accurate in areas with sharp elevation changes. (eg: roadbed cut onto a rocky shelf, or in deep cuttings, etc) Note that 1/9 arc-second data is scarce in many areas.

In the picture below, notice that the background colour of the map has changed, and completely covers the area we have selected for our route.

USGS 3.jpg
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In the picture below, I have selected the higher accuracy, but rarer 1/9 arc/second DEM. Notice that the coverage area is limited in the area we have selected for our route. This would not be enough to generate the terrain we will need in just this DEM type.

USGS 3.5.jpg
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4) After selecting your DEM type, drawing the rectangle around your route, and checking DEM availability, you can now click 'Find Products'.

USGS 4.jpg
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(continued in post below)
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby BoostedFridge » Tue Jan 10, 2017 1:52 am

5) This is the list of each DEM file you will need to generate the terrain for the area you selected.

Click 'download' on each file. If you have a larger route, you will likely have to scroll down to see all of the files.

USGS 5.jpg
USGS 5.jpg (282.93 KiB) Viewed 10330 times



Once you have your files downloaded, use 7zip, Winzip, or Winrar to extract each folder.

The above steps replace pages 2-6 of bnsfsubdivision's excellent DEM terrain tutorial. You can follow through the rest of the process with that tutorial, available here: https://www.dropbox.com/s/t55mnj18alimvlh/Searchlight%20Simulations_Terrain_Import_01_05_17.rar?dl=0
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby imnew » Tue Jan 10, 2017 5:10 am

Nice.! Thanks for creating a updated tutorial on this subject. Much needed and very appreciated. !!*ok*!!
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby _o_OOOO_oo-Kanawha » Tue Jan 10, 2017 12:11 pm

Thanks.

Does this apply to other parts of the world as well, or is only the USA mapped in high definition?
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby TDHenderson » Tue Jan 10, 2017 12:49 pm

Thank you for this!! *!!thnx!!*
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby BoostedFridge » Tue Jan 10, 2017 1:10 pm

_o_OOOO_oo-Kanawha wrote:Does this apply to other parts of the world as well, or is only the USA mapped in high definition?


The USGS has been slowly updating the map to cover DEM for the rest of the world. I have confirmed that some parts of Canada, and Asia are added, but only with 1 arc-second DEM files.
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby TDHenderson » Tue Jan 10, 2017 1:15 pm

Been waiting years for 1/9 arc second terrain of the Black Hills to be released. Probably will be a few more years. The area with 1/3 terrain looks great, but would love them to get to 1/9th. Patience, grasshopper!
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby joeflint » Tue Jan 10, 2017 3:19 pm

Admins
Would it be possible to post this in the Learning Center? I would hate to see this excellent tutorial get lost.
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby Chacal » Wed Jan 11, 2017 1:19 am

I was thinking just that.
I posted it but for some reason no content is showing. I'll fix it later.
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby ErikGorbiHamilton » Sat Jan 20, 2018 11:16 pm

Sorry for the bump but I have run into a issue with this. From what I under stand you need to have a HGT file in order for it to show up. How ever, the only files I get when I use this way to get my DEM data are SHX, SHP, PRJ, and DBF. Do these work in the DEM>SRTM folder?
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby BoostedFridge » Tue Jan 23, 2018 3:05 am

ErikGorbiHamilton wrote:Sorry for the bump but I have run into a issue with this. From what I under stand you need to have a HGT file in order for it to show up. How ever, the only files I get when I use this way to get my DEM data are SHX, SHP, PRJ, and DBF. Do these work in the DEM>SRTM folder?


No.

You need extract the hgt files from the flt files as per the tutorial by BNSFsubsivision.
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby Dakota » Sat May 25, 2019 6:31 pm

By some miracle I found this online directory of the SRTM V2 (high-res 1 arcsecond) HGT data files. Forget wrestling with the National Map Viewer. Unzip, these are 25Mb (high-res) and work perfectly in the RailWorks/TS world editor as SRTM input. Much better than the default 3" ones!!

PS I was reading this page from the Developer Doc but the link leads to low resolution hgt data. The above is the highest resolution SRTM you can get.
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby BoostedFridge » Mon Jun 03, 2019 10:16 pm

Dakota wrote: The above is the highest resolution SRTM you can get.


As noted above, the much higher resolution 1/3 arc second and 1/9 arc second files are available, but need to be ran through the payware ReDem program in order for Railworks/Train Simulator to use them.
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby Dakota » Thu Jun 13, 2019 5:18 pm

ReDem is gone, or at least that's what everything I can find says. "Retracted". Furthermore, if you use the 1" SRTM in anything beyond a trivially small route, you will be TempDumped to death. I gave up eventually after maybe 50 TempDumps on 3x3 to 19x19. If the route is "small", i.e., you are DEMming within 20-30 miles of the reference Lat/Long, then the 1" data works great, very reliable. So it is not the data it is TS2019. Just an FYI.
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Re: TUTORIAL: Downloading DEM / SRTM terrain data

Unread postby DanSSG » Thu Jun 13, 2019 10:22 pm

Dakota wrote:Furthermore, if you use the 1" SRTM in anything beyond a trivially small route, you will be TempDumped to death. I gave up eventually after maybe 50 TempDumps on 3x3 to 19x19.


I can't confirm that. I have no problems importing DEM on my route. With about 135 miles and about 100 tiles west from the route orgin it's not that small *!!wink!!*
Are you working with the 32bit version of TS? Maybe you hit the 3.x gig RAM limit.
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