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Using the Recast function on the LAS function

When a mosaic dataset is created with a LAS function, it is created with specified LAS return types, class types, aggregation, and void filling parameters. To view data with a different set of parameters, use the Recast function to dynamically request the variables with the values that you want to see. This way you can prototype different surface views by adding the Recast function and changing the parameters.

LAS dataset parameters

This section reviews all the parameters of the LAS functions. These are the parameters that you can change.

The variable names used in the LAS function are as follows:

ReturnTypes can be one value from zero to 15 or an array such as [0,1]:

  • 0—First

  • 1—Second

  • …

  • 14—Fifteenth

  • 15—Last

ClassTypes can be one value between zero and nine, or an array such as [3,4]:

  • 0—Never Classified

  • 1—Unclassified

  • 2—Ground

  • 3—Low Vegetation

  • 4—Medium Vegetation

  • 5—High Vegetation

  • 6—Building

  • 7—Noisy Low Point

  • 8—Model Key Point

  • 9—Water

CellAggregationType can be one value between zero and four:

  • 0—Maximum

  • 1—Minimum

  • 2—Mean

  • 3—Sum

  • 4—Mean Distance Weighted

VoidFillMethod can be one value between zero and four:

  • 0: None

  • 1: Simple

  • 2: Plane Fitting/IDW

CellWidth is the pixel size specified as a floating point value.

Triangulation is a value of between zero and one; however, for the LAS function, only 0 (linear) is available.

Use the Recast function to change parameters in LAS functions

Below is a set of steps to use the Recast function to temporarily change parameters, when displaying your LAS Dataset.

  1. Create a mosaic dataset with the LAS raster type and set the Return Types to beLow Vegetation, Medium Vegetation, and High Vegetation.
  2. Use the Add Function tool within the Image Analysis window to open the Function Template Editor.
    1. Click the Windows menu and click Image Analysis.
    2. In the Image Analysis window, highlight the LAS mosaic dataset in the Layer List.
    3. Click the Add Function Add Function button.
  3. Right-click Identify, point to Insert Function, and choose the Arithmetic Function.
  4. Choose the Minus operator. Keep the other parameters as the defaults and click OK.

    In your Function Template Editor window, there is now an Arithmetic function with two inputs. These two inputs are currently both pointing to the mosaic dataset.

  5. Highlight and right-click the first input, point to Insert Function, and click Recast Function.
  6. Set the ReturnTypes value to 0.
    1. Click the Add Item button.
    2. In the Name field, type ReturnTypes.
    3. In the Value field, type 0.
    4. Click OK, to accept the arguments you have set.
  7. Highlight and right-click the second input, point to Insert Function, then click Recast Function.
  8. Set the ReturnTypes value to 15.
    1. Click the Add Item button.
    2. In the Name field, type ReturnTypes.
    3. In the Value field, type 15.
    4. Click OK, to accept the arguments you have set.

    Your Arithmetic Function now has a Recast argument that will be subtracted from another Recast argument.

  9. Click OK on the Function Template Editor window to calculate your result.

The result will be the tree height information from the LAS mosaic dataset.

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