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Gridding/Tiling Operations into Smaller Chunks

Updated

Gridding/Tiling Operations into Smaller Chunks

The following parameters apply to export and other commands that support breaking the operation up into regular tiles of some size rather than generating just a single output:

  • GRID_TYPE_CELL_SIZE - specifies that the export should be gridded into multiple tiles with each tile having the given size in the export projection. The value should be specified as cell width,cell height. For example, if you are exporting in a metric projection and want to tile the export into cells that are 10,000 meters wide by 5,000 meters tall, you would use GRID_TYPE_CELL_SIZE="10000.0,5000.0".
  • GRID_TYPE_PIXEL_SIZE - specifies that the export should be gridded into multiple tiles with each tile having the given size in pixels/samples. The value should be specified as cell pixel width,cell pixel height. For example, if you want to tile the export into cells that are 800 pixels wide by 600 pixels tall, you would use GRID_TYPE_PIXEL_SIZE="800,600".
  • GRID_TYPE_PIXEL_SIZE_MAX - specifies that the export should be gridded into multiple tiles with each tile having the given maximum size in pixels/samples. This works by calculating the number of rows and columns needed to hold cells of the given pixel dimensions, then shrinking those pixel dimensions down so that the tiles exactly cover the exported bounds. The value should be specified as cell pixel width,cell pixel height. For example, if you want to tile the export into cells that are at most 800 pixels wide by 600 pixels tall, you would use GRID_TYPE_PIXEL_SIZE_MAX="800,600".
  • GRID_TYPE_ROWS_COLS - specifies that the export should be gridded into multiple tiles with a given number of rows and columns of tiles. The value should be specified as number of rows,number of columns. For example, if you want to tile the export into a grid of 8 rows each 4 tiles across, you would use GRID_TYPE_ROWS_COLS="8,4".
  • GRID_OVERLAP - specifies how much to overlap tiles when gridding an export into multiple tiles. This is a percentage value from 0 to 100 and only applies when on of the GRID_TYPE_* parameters is used. For example, to make your grid tiles overlap by 5% of the grid tile size, use GRID_OVERLAP="5.0". The default value is 0.0, meaning that the tiles do not overlap.
  • GRID_OVERLAP_NUM_PIXELS - indicates whether or not the value specified in GRID_OVERLAP should be interpreted as a number of pixels instead of a percentage. Use GRID_OVERLAP_NUM_PIXELS=YES to specify that the value specified in the GRID_OVERLAP parameter should be interpreted as a number of pixels. Use GRID_OVERLAP_NUM_PIXELS=NO or omit this parameter to specify that the value is a percentage.
  • GRID_KEEP_CELL_SIZE - specifies that the size of the grid cells should be maintained over sample spacing. This means that if you specify a grid of 4 rows and 5 columns, each grid cell will be exactly 25% of the total export height and 20% of the total export width. The sample spacing may be slightly smaller than what is specified in order to achieve this. By default, the sample spacing is exactly maintained and each grid cell may be slightly larger than specified to maintain an integer number of exported cells. Use GRID_KEEP_CELL_SIZE=YES to enable.
  • GRID_NAMING - specifies how to name tiles when gridding an export into multiple tiles. The value should be SEQUENTIAL for sequential numeric naming starting at 1, SEPARATE for separate prefix appending by row and column, or SEPARATE_COLS_FIRST for separate prefix appending by columns and rows. For the SEPARATE options, use the GRID_NAMING_COLS and GRID_NAMING_ROWS parameters to specify the details of how to name the rows and columns. The value will be appended to FILENAME specified in the EXPORT command. If no GRID_NAMING parameter is supplied, the last selected grid naming options selected in the user interface will be used.
  • GRID_NAMING_COLS - specifies how to name the column portion of grid cell names when using the GRID_NAMING=SEPARATE or GRID_NAMING=SEPARATE_COLS_FIRST parameter. The value of this field is a comma-delimited list with the following field values:
    • Naming type. Can have the following values:
      • NUM - name using numbers in ascending order
      • NUM_REVERSE - name using numbers in descending order
      • ALPHA - name using letters in ascending order
      • ALPHA_REVERSE - name using letters in descending order
    • Starting value for numbering or lettering (i.e. '1', or 'A'). If the naming type is numeric you can also specify %left% or %right% as the starting value to use the left or right coordinate of the cell bounding box. For row naming you can use %top% or %bottom%.
    • Prefix string to use before the numeric or alphabetic value.
    • Step value for numeric naming (default is '1')

    You can leave values blank if they don't apply or you want to use the default. As an example, to do numeric naming starting at the number 100, increasing by 10 each time with a prefix of DEM, you would use GRID_NAMING_COLS="NUM,100,DEM,10".

  • GRID_NAMING_ROWS - specifies how to name the row portion of grid cell names when using the GRID_NAMING=SEPARATE parameter. See the documentation for the GRID_NAMING_COLS parameter above for details on the format.
  • GRID_NAMING_PREPEND_ZEROES - specifies whether or not to prepend zeroes to the start of grid column/row names. Use GRID_NAMING_PREPEND_ZEROES=NO to disable the prepending of zeroes.
  • GRID_NAMING_SEPARATOR - specifies the separator string to use between pieces of a grid name. The default is an underscore (_).
  • GRID_CREATE_FOLDERS - specifies that a separate folder should be generated for each row (or column if GRID_NAMING=SEPARATE_COLS_FIRST is specified) of the export rather than placing every output file in the same folder.
  • Tiling to Polygons/Areas - If you would like to tile your export to a series of polygons/areas, use the POLYGON_CROP_FILE and POLYGON_CROP_USE_EACH parameters. Click the link for details.

Built-in Variables

For any command that breaks up an operation in to multiple pieces using gridding, you can use one of the special character sequences below in a parameter of the command to use a piece of information about the grid cell being exported in the export (i.e. parts of grid cell filename). The examples of what the values will be based on a current grid filename of 'C:\path\to\my\data\my_file_A1.dem' are listed:

  • %TILE_DIR% - full path to current file (value is 'C:\path\to\my\data\')
  • %TILE_FNAME_W_DIR% - full path and filename of current file (value is 'C:\path\to\my\data\my_file_A1.dem')
  • %TILE_FNAME% - filename of current file (value is 'my_file_A1.dem')
  • %TILE_FNAME_WO_EXT% - filename of current file without extension (value is 'my_file_A1')

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