OpenTopography.Org

This data was mostly collected with funding from the National Science Foundation for research programs.  You can get similar data from other locations.

 

Global DEMs: Bulk download gets the original files (except perhaps that the overlap top row and right column will be trimmed out); the cookie cutter option will be reprojected and reinterpolated for the higher latitudes.  Bulk download is overkill as you must get the entire data set, but it is simple if you have the bandwidth and required storage,  You could also figure out how to download just what you want or need, but programmer time is more expensive than bandwidth or storage.

Connect to http://www.opentopography.org/ and pick the "Get data" option.

Preferentially get the red symbol data sets, which are on the OpenTopography web site.

Two ways to pick data:

  • Graphically on the map
  • Search by location
With search by location, you will see a list of surveys.  Use the "Get data" button for the one you want. 
   
With graphical selection on the map, use the blue "Select a region" button to pick a survey, and then pick the "Get data" button.

To see the more complete metadata, use the "More" selector.  This is the only way to see the projection used for the data.  You want to avoid state plane coordinates to the maximum extent possible.  You might want to save this metadata for later review.  
The page for a data set has abbreviated metadata.  It will give the following key information:
  • Survey date (pay attention to the season, as leaf on and leaf off are very different in terms of the lidar characteristics)
  • Survey area size
  • Point density.  Early surveys were often <1 pts/m; current surveys can be > 15 pts/m.  This number will be an average; vegetation has a higher density because each pulse can have multiple returns in the vegetation canopy.

The full metadata option includes the projection.  You want to avoid state plane coordinates to the maximum extent possible.

Use the blue "Select a region" button to pick the region.  Watch the status window below the map, which will tell you approximately how many points are in the region.   You must keep reducing the area until you get under you point limit.  If you really need more data, you should register for an account.
When you have reduced the number of points sufficiently, set the terms of the download:
  1. Get all return classifications.
  2. Request the point cloud in LAZ format, which will be about 10% of the size of the alternatives but requires that you have LAStools (read license carefully).
  3. If you want local gridding, change the grid format to GeoTiff. Alternatively MICRODEM can generate a grid from the point cloud.
  4. If you want DEM generation via TIN, change the grid format to GeoTiff.  You can create your own grids in MICRODEM
  5. Do not get derivative DEM or TIN products; MICRODEM can generate these rapidly on the fly.
  6. Do not get Visualization.
  7. You can get Hydrologic terrain analysis products from TauDEM, which require some of the optional grids.

Enter a job description and title.

Enter you email.

Submit the job.

 
You can stay on the page and watch the progress, or wait for the email which will have download links.

When done, you can download your files.  Note the file names "points" and "dems" are used for every download, so insure you do not mix them on your hard disk.  Put each area in a separate directory.

The point cloud will be in the format you requested; use LAStools to uncompress the LAZ file.

If the points file is really large, you can split it into smaller sections.  This will make the display of subsets of the data much faster.

If you do not wait for you downloads to be prepared, you will get an email, which will direct you back to the page above.
Notes on global DEMs  

AWS Bulk downloads.  There is an option to do bulk downloads after you have selected an OpenTopography data set.  You should only do this if you have to download a very large area.

  • Install  https://docs.aws.amazon.com/cli/latest/userguide/install-cliv2-windows.html
  • The popup window when you pick the bulk download for a data set gives the command you want, which will be something like:
    •  aws s3 cp s3://pc-bulk/NAPA_2014/ . --recursive --endpoint-url https://opentopography.s3.sdsc.edu --no-sign-request
  • Files will be downloaded to the directory from which you run the DOS command, so plan accordingly and have lots of free disk space (100s of MB is not out of the realm of possibility).
  • Enter that command in a DOS command prompt.  If this is not in your PATH,  add the path and enclosing the EXE name (aws) in quotes because of the space in "program files", as in
    • "C:\Program Files\Amazon\AWSCLIV2\aws" s3 cp s3://pc-bulk/NAPA_2014/ . --recursive --endpoint-url https://opentopography.s3.sdsc.edu --no-sign-request
  • At an initial period of inactivity, the command prompt window will show you the progress of the downloads. The anticipated file size and number of files remaining is likely to creep upward (perhaps by an order of magnitude or more, so what starts out looking like a 10 GB download balloons to 120 GB) while the download progresses, so multitask or take a break and don't watch too closely.
  • The lidar files will be in LAZ format, which you must uncompress to use
  • There may also be LAX indexed files, which MICRODEM does not use but some software might.



Last revised 1/26/2022