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:
| Parameters | Description | Requirements |
| NCOLS | Number of columns | Integer greater than 0 |
| NROWS | Number of cell rows | Integer greater than 0 |
| XLLCENTER or XLLCORNER | X coordinate of the origin (by center or lower left corner of the cell) | Match with Y coordinate type |
| YLLCENTER or YLLCORNER | Y coordinate of the origin (by center or lower left corner of the cell) | Match with X coordinate type |
| CELLSIZE | Cell size | Greater than 0 |
| NODATA_VALUE | The input values to be NoData in the output raster | Optional. Default is -9999 |
For the cell value data after the header information: