Monday, March 9, 2020

Using Saga GIS' Terrain Analysis Swath Profile (interactive) function

Saga GIS has a couple of interactive terrain profiling functions, a single profile and a swath profile. This post shows how to use the interactive swath terrain profile command.

Load a grid file such as a USGS SRTM file
  1. Run Saga GIS. Select Geoprocessing | File | Grid | Import | Import USGS SRTM Grid.

    The Import USGS SRTM Grid dialog box appears.
  2. Click the Browse button in the Files field. Choose an SRTM file e.g. N21E093.hgt.

  3. Click Open.

  4. Click Okay.

    The SRTM file is loaded and shown in the Data tab.
Start the swath profile command
  1.  Under the Data tab, mouse right click on the loaded grid file e.g. N21E093.
  2. In the pop up context menu, choose Add to Map.

    The grid file is displayed in a map window.
  3. Select Geoprocessing | Terrain Analysis | Profiles | Swath Profle [Interactive].

    The Swath Profile dialog box appears.
  4. In the Grid system field, choose the loaded grid file's system e.g. 0.000833; 1201x 1201y; 93x 21y option.
  5. In the DEM field, choose the loaded grid file, e.g. N21E093.
  6. Optional. Change the Swath Width if necessary.

    The message Interactive tool execution has been started is displayed in the Messages pane.
Digitize the swath profile
  1. In the Toolbar, click the Action icon (that looks like a black NW arrow).
  2. In the map window, click a few points to draw the swath profile.

  3. To complete the drawing, press the mouse right button.
  4. To exit the interactive command, select Geoprocessing | Swath Profle [Interactive].

    The Tool Execution prompt appears.
  5. Click Yes.

    The message: "Interactive tool execution has been stopped" is shown in the Messages pane.

    Note: This may take a while as the command will sample the terrain to calculate the points.
Display the swath profile graphically
  1.  In the Data pane, mouse right click on the newly created profile points e.g. Profile [N21E093].

  2. In the pop up menu, choose Attributes | Diagram.

    The Properties dialog box appear.
  3. In the X Axis Values field, choose D (for Distance).
  4. In the X Axis Label field, choose D.
  5. In the Attributes field, toggle on Z, Z [min], Z[max].
  6. Set other options if necessary.
  7. Click Okay.

    The profile line(s) are displayed.

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