ArcMap

Raster to ASCII

Summary

Converts a raster dataset to an ASCII text file representing raster data.

Usage

  • The input raster dataset can be any valid raster dataset.

  • The structure of the ASCII file consists of header information containing a set of keywords, followed by cell values in row-major order.

    The format of the file in general is:

        NCOLS xxx
    NROWS xxx
    XLLCORNER xxx
    YLLCORNER xxx
    CELLSIZE xxx
    NODATA_VALUE xxx
    row 1
    row 2
    .
    .
    row n

    The definitions of the keywords are as follows:

    • NCOLS and NROWS are the number of columns and rows in the raster defined by the ASCII file.

    • XLLCORNER and YLLCORNER are the coordinates of the lower left corner of the lower left cell.

    • CELLSIZE is the cell size of the raster.

    • NODATA_VALUE is the value that is to represent NoData cells.

    • In the data stream of cell values, row 1 of the data is the top of the raster, row 2 is just under row 1, and so on.

  • An example of an ASCII raster file is:

        NCOLS 480
    NROWS 450
    XLLCORNER 378922
    YLLCORNER 4072345
    CELLSIZE 30
    NODATA_VALUE -32768
    43 2 45 7 3 56 2 5 23 65 34 6 32 54 57 34
    35 45 65 34 2 6 78 4 2 6 89 3 2 7 45 23 5 ...

  • The NODATA_VALUE is the value in the ASCII file that will represent cells that are NoData in the input raster. This value is normally reserved for those cells whose true value is unknown.

  • The end of each row of data from the raster is terminated with a carriage return character in the file.

  • Both integer and floating point rasters can be converted to an ASCII raster file.

  • This tool only writes the origin as the lower left corner of the lower left cell. The ASCII to Raster tool also supports the origin as the center of the lower left cell.

Syntax

arcpy.conversion.RasterToASCII(in_raster, out_ascii_file)
ParameterExplanationData Type
in_raster

The input raster dataset.

The raster can be integer or floating-point type.

Raster Layer
out_ascii_file

The output ASCII raster file.

File

Code sample

RasterToASCII example (Python window)

Converts a raster dataset to an ASCII file representing raster data.

import arcpy
from arcpy import env
env.workspace = "c:/data"
arcpy.RasterToASCII_conversion("elevation", "c:/output/sa500.asc")
RasterToASCII example (stand-alone script)

Converts a raster dataset to an ASCII file representing raster data.

# Name: RasterToASCII_Ex_02.py
# Description: Converts a raster dataset to an ASCII file representing 
#    raster data. 
# Requirements: None

# Import system modules
import arcpy
from arcpy import env

# Set environment settings
env.workspace = "C:/data"

# Set local variables
inRaster = "elevation"
outASCII = "c:/output/elevation.asc"

# Execute RasterToASCII
arcpy.RasterToASCII_conversion(inRaster, outASCII)

Environments

Licensing information

  • Basic: Yes
  • Standard: Yes
  • Advanced: Yes

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