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Change Map

Using the Change Map analytic is a convenient way to compare and analyze two different time-series DSMs, from successive aerial surveys, of a same location in order to reveal and measure change in the site configuration.

It is especially useful as a component of quarries and open pit mines production and management, for extracted material follow-up, waste dump, or again in construction activities. 

Representing a cross-section, the color chart is :

  • Negative (Cut) values are displayed in red scale
  • Positive (Fill) values are displayed in blue scale


1. What are the required inputs ?

Your Site (i.e. one of your project within one of your companies) shall contain at least two DSMs of the same location, in two separate surveys, to compute the change over time from this same geographical scene.


2. Running a Change Map calculation

a. Select a Survey within your Site that contains a DSM (in case you select a survey without DSM, you will be prompted for this at next steps). Go to Analytics from the left panel :

b. Scroll down to Change map section and then press Run :

c. Then select the DSMs to be compared :

d. Press Launch change map button :


3. How is it displayed ?

Go to Base Layers section in the left panel Select and click in the Change Map generated raster to open the right panel:

On the map and in right panel:

  • Negative (Cut) values are displayed in red scale
  • Positive (Fill) values are displayed in blue scale


4. Change Map Exploration

4.1. Elevation difference range adjustment

It is possible to adjust the range of visible elevation difference computed between the two surveys. It will update the change map displayed and the Cut and Fill volumes indicated. Using either the slider bars on Cut and Fill or a manually input value :

4.2. Value at Point

Use “Value at point” feature to request the raster value (elevation difference) clicking in any point of the map :


4.3. Extraction from a Point annotation

You may use an annotation point to extract all raster values under the point and compare the DSM values.

Open the point annotation right panel, go to Info section then press Extract data :


5. Deliverables

Three files are generated as deliverables, and can be exported if necessary from the Downloads section :

  1. A vector geojson file containing the polygon vectorized from the raster result in terms of Fill (positive values)
  2. A vector geojson file containing the polygon vectorized from the raster result in terms of Cut (negative values)
  3. A raster tif file representing the height difference between both DSMs compared


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