InfoDrainage can import surface data from Esri ASC files. 

The *.ASC file extension denotes an Esri ArcGIS geographic information system output file. This contains comma-delimited data in ASCII text format which defines map surface data. 

The ASC file structure contains the header information at the start of the file, followed by the cell value data. 

The following defines the ASC file Header parameters: 

ParametersDescriptionRequirements
NCOLSNumber of columnsInteger greater than 0
NROWSNumber of cell rowsInteger greater than 0
XLLCENTER or XLLCORNERX coordinate of the origin (by center or lower left corner of the cell)Match with Y coordinate type
YLLCENTER or YLLCORNERY coordinate of the origin (by center or lower left corner of the cell)Match with X coordinate type
CELLSIZECell sizeGreater than 0
NODATA_VALUEThe input values to be NoData in the output rasterOptional. Default is -9999

For the cell value data after the header information:

  • Values should be comma-delimited
  • Since the NCOLS parameter defines the number of columns, it's not necessary to have a carriage return to start the next row