Maps Made Easy Drones Made Easy

Arbitrary DEM Preparation for use as a Custom Terrain Source

Tudor -

Bring your own Terrain.

This is an advanced user activity.

Map Pilot can use terrain model data that is created by processing imagery in Maps Made Easy. Every time a job is run in Maps Made Easy a digital elevation model (DEM) is created. From this DEM Maps Made Easy also creates a set of depth tiles that are optimized for use in making volume measurements. Map Pilot can also make use of these tiles as an elevation reference for Terrain Aware flight with a Custom Terrain Source.

You can read more about that here: https://support.dronesmadeeasy.com/hc/en-us/articles/360000745623-Custom-Terrain-Source-for-Terrain-Awareness 

Maps Made Easy is now capable of accepting externally hosted DEM files (TIF or IMG) in various projections for processing into a Map Pilot compatible Custom Terrain Source. 

You must have an active Maps Made Easy subscription to have access to this feature. For amounts beyond the subscription's terrain processing threshold, this processing is available 2 Maps Made Easy points per acre.

The acreage is measured from corner to corner of the entire file, not just active pixel area, so be sure to crop appropriately.  

Some users will create their own DEM files using LiDAR or other survey means, but there is also a bunch of publicly available data out there that is more recent and higher resolution than the SRTM data Map Pilot offers by default. Here is a quick example of how to prepare the data and trim it to a reasonable size for processing. 

Here is a general overview of the steps involved:

  1. Download DEM data.
  2. Open the data in QGIS.
  3. Crop the data to a reasonable size.
  4. Subscribe to Maps Made Easy. 
  5. Use the 'New Custom Terrain' link under the Map Pilot heading in the top menu. 
  6. Upload your TIF/IMG file.
  7. Wait for the processing to complete. 
  8. Use the newly created Custom Terrain Source as shown in the link above. 

 

NOTE: You can provide your own DEMs, they do not need to come from public data sources like they do in this example. When preparing your own data you can skip to Step #3. We require the data to be supplied in WGS84 EPSG:4326 data. Please make sure your elevation source data is in metric units. 

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1. Download DEM Data

Visit https://viewer.nationalmap.gov/basic/ and enter the location you would like to get data for. Most of the files are pretty big so don't worry about getting super close yet. 

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In the menu on the left side, check the types of data you would like to find for this location. 

 

Then click "Find Products" in the popup by the pinned location.

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Then click on 'Download' for files you want on the left. 

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Download the elevation data for the area that includes your area of interest. You can click on 'Footprint' to see the actual areas each covers on the map. The middle one was downloaded for this example since it is the one that included the intended flight area. 

This sample data is roughly 3m/pixel elevation data. The standard SRTM data is 30m/pixel.

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2. Open the data in QGIS.

Drag the .img file from the downloaded elevation zip file into the QGIS window.

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When you first drag it in the data won't likely be scaled properly to show the terrain. Right click on the file in the 'Layers' window and select 'Properties.'

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Then select 'Singleband pseudocolor' and enter some minimum and maximum numbers in the 'Generate new color map' area. Hit classify and then OK and the map will be colorized. It might take some experimentation to get the area you are interested in to be shaded properly. 

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This is what a properly elevation classified map will look like. 

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To aid in orientation it can be helpful to add a hillshade layer. To do this, select the layer in the 'Layers' window again and select 'Raster' -> 'Analysis' - > 'DEM' at the top. 

Enter a 'Output file' name with a valid path. Make sure 'Hillshade' is selected and hit OK.

The following layer will be added to the 'Layers' window. 

Screen_Shot_2019-01-16_at_4.58.21_PM.png

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3. Crop the data to a reasonable size

Now that there is a little more recognizable detail available, pan and zoom around to find the area you want to use as your Custom Terrain Source. Remember: You are paying for it so be efficient. Don't make a DEM that is way larger than you actually need. 

Go to 'Raster' -> 'Extraction' -> 'Clipper' to bring up the Clipper tool. Enter an output file name with a valid path (preferably a .tif file). This will be the name  of your output file that gets uploaded to your hosting. Make sure the DEM (not the hillshade) layer is selected. Then select the area you would like to crop to your new DEM. 

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Here you can see the my_clipped_dem.tif in the 'Layers' window. 

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The my_clipped_dem.tif file is ready for upload to your hosting. 

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4. Subscribe to Maps Made Easy

Terrain processing is included in our subscriptions. If you need more terrain processing than is included with your subscription you can use purchased points. Only purchased points are available to work with Custom Terrain Processing. You can get them here: https://www.mapsmadeeasy.com/buy_points

Maps Made Easy will charge 2 points for every acre that is represented in your Custom Terrain DEM file. The whole rectangle is counted. 

If there are not enough points in the account to process the DEM it will fail. 

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5. Upload your TIF/IMG file

Use the 'New Custom Terrain' page and upload your data. 

Or... You can use the API directly. (advanced users only)

Mac OS:  curl -H "Authorization: Token XXXXXXXXXXXXXXXXX" -H 'Content-Type: application/json' -X POST -d '{"url": "https://s3-us-west-1.amazonaws.com/YOUR_BUCKET/westside.tif"}' https://www.mapsmadeeasy.com/api/v1.1/new_dem/

Windows: curl -H "Authorization: Token XXXXXXXXXXXXXXXXX" -H "Content-Type:application/json" -X POST -d "{ \"url\": \"https://www.dropbox.com/s/fjeiafojei/westside.tif?dl=1\"}" https://www.mapsmadeeasy.com/api/v1.1/new_dem/

Your Access Password comes from your Maps Made Easy account's Profile page. 

Dropbox works. FTP works. Web file servers work. Google Drive does not work. This system requires a link that directly downloads the file without redirection. 

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7. Wait for the processing to complete

You will receive an email when the processing starts and when it finishes. 

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8. Use your new Custom Terrain Source

Done! (this one is slightly larger than the example above)

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You can see this map in with the rest of your maps in your Maps Made Easy Dashboard. 

Read more here about how to set it up to use it in Map Pilot:

https://support.dronesmadeeasy.com/hc/en-us/articles/360000745623-Custom-Terrain-Source-for-Terrain-Awareness 

 

 

 

 

 

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