COMBINE_TERRAIN

The COMBINE_TERRAIN command generates a new terrain (gridded elevation) layer by combining two loaded terrain layers through some operation, like addition, subtraction (difference), average, min/max, etc. The new terrain layer can then be operated on just like any other terrain layer.

The following parameters are used by the COMBINE_TERRAIN command:

  • LAYER1_FILENAME - full path and filename of the first loaded terrain layer to use. You can also pass in the full description of the loaded layer to use in case you want to use a layer not loaded from a file. If you are using one of the combine operations that works on multiple layers in a single list, like ADD, AVERAGE, MINIMUM, MAXIMUM, or COUNT_VALID, you can leave this blank and have all loaded layers examined.
  • LAYER2_FILENAME - full path and filename of the second loaded terrain layer to use. You can also pass in the full description of the loaded layer to use in case you want to use a layer not loaded from a file. You do not have to provide this for those operations that work on multiple layers in a single list, like ADD, AVERAGE, MINIMUM, MAXIMUM, or COUNT_VALID.
  • COMBINE_OP - defines the operation to perform when combining the layers. The following operations are supported:
    • ADD - adds the values from the first layer to the second
    • SUBTRACT_SIGNED - subtracts the values of the second layer from the first and saves the signed result.
    • SUBTRACT_UNSIGNED - subtracts the values of the second layer from the first and saves the magnitude of the result.
    • AVERAGE - saves the average of the values from the first and second layers.
    • MINIMUM - saves the smaller of the values from the first and second layers.
    • MAXIMUM - saves the larger of the values from the first and second layers.
    • MULTIPLY - multiplies the values from the first and second layers. If one or both of the values is missing, the sample is marked as invalid.
    • DIVIDE - divides the value from the first layer by the value in the second layer. If one or both of the values is missing or if the second value is 0, the sample is marked as invalid.
    • FILTER_KEEP_FIRST - saves the first layer value if the second layer value is valid.
    • FILTER_KEEP_FIRST_IF_SECOND_INVALID - saves the first layer value if the second layer value is invalid
    • FILTER_KEEP_FIRST_IF_GT_SECOND - saves the first layer value if the second layer value is valid and the first layer value is greater than the second layer value.
    • FILTER_KEEP_FIRST_IF_LT_SECOND - saves the first layer value if the second layer value is valid and the first layer value is less than the second layer value.
    • FILTER_KEEP_FIRST_IF_SECOND_GT_VAL - saves the first layer value if the second layer value is valid and the second layer value is greater than the value provided with the COMPARE_VAL parameter
    • FILTER_KEEP_FIRST_IF_SECOND_LT_VAL - saves the first layer value if the second layer value is valid and the second layer value is less than the value provided with the COMPARE_VAL parameter
    • COUNT_VALID - counts the number of layers that have a valid sample at each grid location. This works with both raster and elevation data.
  • COMPARE_VAL - provides a numeric value to compare against for some of the combine operations above.
  • LAYER_DESC - specifies the name to assign to the newly generated terrain layer. If no layer description is provided, the default name of "Combined Elevation Grid" will be used.
  • ELEV_UNITS - specify elevation units to use in new terrain layer
    • FEET - export in US feet
    • DECIFEET - export in 10ths of US feet
    • METERS - export in meters
    • DECIMETERS - export in 10ths of meters
    • CENTIMETERS - export in centimeters
  • SPATIAL_RES - specifies spatial resolution. Defaults to the minimum spatial resolution of the two layers if not specified. Should be formatted as x_resolution,y_resolution. The units are the units of the current global projection. For example, if UTM was the current global projection and you wanted to export at 30 meter spacing, the parameter/value pair would look like SPATIAL_RES=30.0,30.0. You can also specify as a percentage of the default resolution by adding a percent. For example to get half the detail your double the spatial resolution value, so you would use SPATIAL_RES="200%,200%".
  • SPATIAL_RES_METERS - specifies spatial resolution to use in meters. The value in meters will automatically be converted to the current view/export projection units. For example, to do an export at 2.0 meter spacing (or as close as you can get to that in the current units), use SPATIAL_RES_METERS=2.0, or to do an export at 1.0 meters in X by 1.5 meters in Y, use SPATIAL_RES_METERS="1.0,1.5".
  • FILL_GAPS - specifies that small gaps in between and within the data sets being combined will be filled in by interpolating the surrounding data to come up with an elevation for the point in question. This option is off by default, specify FILL_GAPS=NO to turn off.

  • See also Specify Bounds for Operation

    • GLOBAL_BOUNDS - specifies the combine bounds in units of the current global projection. There should be 4 values in a comma-delimited list following the parameter name. The values should be in order of minimum x, minimum y, maximum x, maximum y.
    • GLOBAL_BOUNDS_SIZE - specifies the combine bounds in units of the current global projection. There should be 4 values in a comma-delimited list following the parameter name. The values should be in order of minimum x, minimum y, width in x, width in y.
    • LAT_LON_BOUNDS - specifies the combine bounds in latitude/longitude degrees. There should be 4 values in a comma-delimited list following the parameter name. The values should be in order of west-most longitude, southern-most latitude, eastern-most longitude, northern-most latitude.
    • LAYER_BOUNDS - specifies that the operation should use the bounds of the loaded layer(s) with the given filename. For example, to export to the bounds of the file "c:\test.tif", you would use LAYER_BOUNDS="c:\test.tif". Keep in mind that the file must be currently loaded.
    • LAYER_BOUNDS_EXPAND - specifies that the operation should expand the used LAYER_BOUNDS bounding box by some amount. The amount to expand the bounding rectangle by should be specified in the current global projection. For example, if you have a UTM/meters projection active and want to expand the bounds retrieved from the LAYER_BOUNDS parameter by 100 meters on the left and right, and 50 meters on the top and bottom, you could use LAYER_BOUNDS_EXPAND="100.0,50.0". You can also specify a single value to apply to all 4 sides, or supply 4 separate values in the order left,top,right,bottom.
    • SNAP_BOUNDS_TO_MULTIPLE - specifies that the top-left corner of the bounding box for the operation should be snapped to a multiple of the given value. For example, using SNAP_BOUNDS_TO_MULTIPLE=1 will snap the top-left corner to the nearest whole number. The values will always go smaller for X/easting/longitude and larger to Y/northing/latitude so you always get at least what is requested.
    • SNAP_BOUNDS_TO_SPACING - specifies that the top-left corner of the bounding box for the operation should be snapped to a multiple of the resolution of the operation. For example, if you are exporting at 5 meter spacing, the top left corner will be snapped to the nearest multiple of 5. Use SNAP_BOUNDS_TO_SPACING=YES to enable or SNAP_BOUNDS_TO_SPACING=NO to disable. If not provided, the global setting for snapping exports to the nearest sample spacing boundary from the Advanced section of the General tab of the Configuration dialog will be used.
    • USE_EXACT_BOUNDS - specifies that the exact bounds that were defined in the command should be used. Generally, when the bounds specified in a command are not the same as the data bounds, the command uses the intersection between the two. When USE_EXACT_BOUNDS=YES is specified, the command will use the bounds as specified, instead of the intersection.

  • See also Cropping Operations to Polygons/Areas

    • POLYGON_CROP_FILE - specifies the full path and filename or loaded layer description of a vector file/loaded layer containing one or more polygon features to which the operation should be cropped. If multiple polygons are found in the specified file the polygon which has the largest intersection with the data to be combined will be used as the crop polygon (see POLYGON_CROP_USE_ALL or POLYGON_CROP_USE_EACH for exceptions).
    • POLYGON_CROP_FILE_PROJ - specifies the projection to use for the POLYGON_CROP_FILE. Use if the file doesn't have an associated projection file. See special Projection Specification for instructions.
    • POLYGON_CROP_NAME - specifies the name of a polygon shape previously defined using the DEFINE_SHAPE command to which the export should be cropped. The coordinates in the shape need to have been provided in whatever projection the new terrain layer will be in (i.e. the current projection). If you want to crop to any area features that are selected with the Digitizer Tool in the user interface rather than a defined polygon, use POLYGON_CROP_NAME="SELECTED".
    • POLYGON_CROP_USE_ALL - specifies that if a POLYGON_CROP_FILE is specified that contains multiple polygons, the operation will be cropped to all polygons in that file rather than just the best-fit polygon.
    • POLYGON_CROP_USE_EACH - specifies that if a POLYGON_CROP_FILE is specified that contains multiple polygons, the operation will generate a separate export for each polygons in that file rather than just the best-fit polygon. See the POLYGON_CROP_BBOX_ONLY and POLYGON_CROP_NAME_ATTR options for naming and other options when using this parameter. Use POLYGON_CROP_USE_EACH=YES to enable. This parameter also works with FEATHER_BLEND_EDGES. Use POLYGON_CROP_USE_EACH=YES with FEATHER_BLEND_POLY_FILE or FEATHER_BLEND_POLY to feather the edges of multiple polygons.
    • POLYGON_CROP_EXCLUDE - specifies that the crop areas are actually regions to exclude from the export rather than include. If you add POLYGON_CROP_EXCLUDE=YES to the command the results will contain everything outside the crop areas but within the full export bounds.
    • POLYGON_CROP_COMBINE_DUPS - specifies that if a POLYGON_CROP_FILE is specified that contains multiple polygons and POLYGON_CROP_USE_EACH is set, whether or not polygons with duplicate values for the attribute used for filenaming will be combined into a single export or split into separate exports. The default is POLYGON_CROP_COMBINE_DUPS=YES.
    • POLYGON_CROP_BBOX_ONLY - specifies that if the POLYGON_CROP_USE_EACH parameter is specified that each export should just be cropped to the bounding box of each polygon rather than the actual boundary of the polygon. Use POLYGON_CROP_BBOX_ONLY=YES to enable only cropping to the bounding box.
    • POLYGON_CROP_GRID_ONLY - specifies that any crop polygon(s) are used only to determine which tile/grid cells will be exported. For each tile/grid cell that intersects a crop polygon, the full tile/grid cell will be exported. Use POLYGON_CROP_GRID_ONLY=YES to enable.
    • POLYGON_CROP_INT_DATA_BOUNDS - control how the bounding box for the export is determined if a crop polygon is specified. If this option is disabled, the export bounds will be the bounds of the crop area(s), even if they extend outside the data bounds, unless you explicitly specified a bounding box in the other parameters (i.e. LAYER_BOUNDS, GLOBAL_BOUNDS, etc.). If the option is enabled, the export bounds will be the intersection of the crop area bounds and the non-cropped bounding box (i.e. full data bounds or specified bounds in other parameter). This parameter is enabled by default, use POLYGON_CROP_INT_DATA_BOUNDS=NO to disable.
    • POLYGON_CROP_NAME_ATTR - used to control the filenames generated when cropping to multiple polygons using the POLYGON_CROP_USE_EACH parameter. See special Attribute Name parameter details. This value will be appended to any filename specified in the EXPORT FILENAME parameter. If no value is provided, the exported files will be sequentially numbered.
    • POLYGON_CROP_FOLDER_ATTR - used to control the filenames generated when cropping to multiple polygons using the POLYGON_CROP_USE_EACH parameter. See special Attribute Name parameter details.
    • POLYGON_CROP_FILENAME_SUFFIX - specifies the text to insert in the output filename just before the file extension when cropping to polygons. For example, if you add POLYGON_CROP_FILENAME_SUFFIX="_out", the original FILENAME was "my_file_.dem" and the value from the polygon was "A1", you would get an output filename of "my_file_A1_out.dem".
    • POLYGON_CROP_COMPARE_STR - specifies a compare string to use to filter out the areas in the polygon crop file. See the COMPARE_STR parameter for the EDIT_VECTOR script command for details.