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GENERATE_BREAKLINES

Marius Lazar
Updated

GENERATE_BREAKLINES

The GENERATE_BREAKLINES command allows for the generation of breaklines from any or all currently loaded elevation data. The following parameters are supported by the command.

  • FILENAME - filename of the loaded terrain layer(s) to find breaklines in. If an empty value is passed in, all loaded terrain data will be used. This parameter can be listed more than once to specify multiple input files, like FILENAME="FILENAME_1" FILENAME="FILENAME_2".

  • LAYER_DESC - specifies the name to assign to the generated breakline layer. If no layer description is provided, a default name will be used based on what was last used on the Breakline dialog

    • METHOD – specifies the method/algorithm used to find the breaklines. Supported values are:

    • SLOPE_EDGES – find breaklines at the edge of flat regions. Use the MAX_FLAT_SLOPE parameter to define what is considered ‘flat’.

    • CURVATURE_EDGES – find breaklines at the edge of regions with little to no curvature (i.e. no change in slope). Use the MAX_FLAT_CURVATURE parameter to define what is ‘flat’.

    • CANNY_EDGES – find breaklines wherever there is a significant change in the curvature (or slope if selected)

  • ELEV_UNITS - specify elevation units to save with the breakline vertices. The elevation values will be pulled from the terrain layer(s). The default is ELEV_UNITS=METERS.

    • FEET - US survey feet

    • METERS - meters

  • SPATIAL_RES_METERS - specifies spatial resolution to use in meters. The calculations will always be done based on samples/cells that are the same number of meters on each side. If not specified, the default resolution for the data set will be used.

  • MIN_BREAKLINE_LEN – specifies the minimum length (in meters) of breakline to keep at the end of the process. Any breaklines shorter than this length will be marked as deleted.

  • GAUSSIAN_BLUR_SIZE – specifies the size of Gaussian Blur to perform on the terrain data before calculating slope or curvature grids. A blur size of 3, 5, or 7 is supported. Use a value of 0 or 1 to disable the blur.

  • SMOOTH_FEATURES – smooth the generated breaklines. Use SMOOTH_FEATURES=NO to disable smoothing

  • MAX_FLAT_SLOPE – specifies the maximum slope (in degrees) that is considered ‘flat’ when using METHOD=SLOPE_EDGES. The default is MAX_FLAT_SLOPE=1.0.

  • MAX_FLAT_CURVATURE – specifies the maximum curvature (in radians / meter) that is considered ‘flat’. These values tend to be very close to 0. The default is MAX_FLAT_CURVATURE=0.005.

  • GAP_FILL_SIZE – specifies how large of a gap in the slope / curvature data that will be filled. The default value is GAP_FILL_SIZE=2. Use GAP_FILL_SIZE=0 to disable gap filling.

  • MIN_FLAT_CELL_COUNT – specifies the minimum number of cells that must be connected in a ‘flat’ area to treat the edge as a breakline. Applies when using METHOD=CURVATURE_EDGES. Any connected flat regions with less than this value will be ignored.

  • CURVATURE_TYPE – specifies the curvature algorithm to use for the CURVATURE_EDGES and CANNY_EDGES methods. The default is CURVATURE_TYPE=STANDARD. The following values are supported:

    • PROFILE

    • PLANFORM

    • STANDARD

    • LONGITUDINAL

    • CROSS-SECTIONAL

    • SLOPE – edges will be found in a slope grid rather than a curvature grid

  • EDGE_THRESHOLDS – specifies the edge thresholds for the CANNY_EDGES method. This value consists of 2 comma-separated numbers, in the format EDGE_THRESHOLDS=”detect_threshold,connect_threshold”. The detect_threshold controls how significant an edge needs to be in order to be treated as an edge. Smaller numbers mean more less significant edges will be found. The connect_threshold specifies how significant non-edge pixels need to be in order to connect pixels that are >= the detect_threshold. The default value is EDGE_THRESHOLDS=”250,100”

 

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