Agisoft Photogrammetric Software: Basic Training - Performing Measurements on the DEM/Ortho View

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DEM/Ortho View

  • Agisoft Photogrammetric Kit for Topcon also supports DEM-based point, distance, area, and volume measurements, as well as generating cross-sections for a part of the scene selected by the user.
  • Additionally, contour lines can be calculated for the model and depicted over DEM and Ortho views.
  • Measurements on the DEM or Ortho view are controlled with shapes: points, polylines and polygons.

Point Measurment

 

  • The DEM or Ortho views allow the user to measure coordinates of any point on the reconstructed model.  X and Y coordinates of the point indicated with the cursor as well as height of the point above the vertical datum selected are shown in the bottom right corner of the view.
  • Using the Point utility icon found in the toolbar, a point shape can similarly be created with the coordinates being displayed after right-clicking and selecting Measure…

Distance Measurments

Distance measurements can be done within the DEM by the use of the ruler utility or with shapes.

  • Measure distance with Ruler
    • Select the Ruler icon from the toolbar
    • Click on the point of the DEM where the measurement should be started.  Upon the second click, the distance between the indicated points will be shown within the Ortho view. 
    • To complete the measurement press Esc key on the keyboard.  

 

  • Measure distance with shapes
    • In the DEM or Ortho view, use the Draw Polyline utility from the toolbar
    • Clicking within the view will create vertices for the polyline, Double click on the last point to indicate the end of the line.
    • With the line selected, Right-click and select the Measure… command

 

  • In the Measure Shape dialog box inspect the results.
  • Under the Planar tab, the Perimeter value equals the distance that has been measured.
  • In addition to polyline length value, coordinates of the vertices are displayed.

Distance measurements can be done within the DEM or Ortho views by the use of the ruler utility or with shapes
 

Measure distance with Ruler:

  • Select the Ruler icon from the Toolbar
  • Click on the point of the DEM where the measurement should be started from.  Upon the second click, the distance between the indicated points will be shown within the Ortho view.  
  • To complete the measurement press Esc key on the keyboard.  


Measure distance with shapes:

  • Connect the points of interest with a polyline.  This can be done using the Draw Polyline tool
  • Double-click on the last point to indicate the end of the polyline.
  • Right-click on the polyline and select the Measure... command from the context menu.
  • The results are then displayed in the Measure Shape dialog, where the Perimeter value equals to the distance that was measured.

Surface Area and Volume Measurements

  • Draw a polygon on the DEM or Ortho using the Draw Polygon instrument to indicate the area to be measured.
  • With the polygon selected, Right-click on the polygon and select Measure... from the context menu that is displayed.
  • In the Measure Shape dialog, the results are displayed. 
  • For volume, select the Volume tab.  This will be calculated from a base plane, which by default is set to a Best fit plane. 
  • However, using the drop down list within this tab, the base plan can be changed to a mean elevation level or a custom level.

Cross Sections

  • To calculate cross sections:
    • Shapes are used define the plane parallel to the
    • Z-axis.  The program will calculate profiles along all the edges starting from the first vertex.
    • Indicate a line to make a cut of the model using Draw Polyline / Draw Polygon tool(s)
    • With the shape created, right-click and select Measure...
    • Results are displayed within the Profile tab

Contour Lines

  • To generate contours
    • Select Generate Contours... command from Tools menu.
    • In the Generate Contours dialog, set values for minimal and maximal altitudes, as well as the interval to be used.  All values should be indicated in meters.  Click OK once finished.
    • When the procedure has completed, a contour lines label will be added to the project file structure shown on the Workspace pane.
       
  • Contour lines can be shown over the DEM or orthomosaic within the Ortho View.
  • Use the Show contour lines tool (shown in diagram oulined in red) located in the toolbar to toggle the view on and off.
  • Contour lines can also be deleted using Remove Contours command from the contour lines label context menu on the Workspace pane.