Raster to ASCII (Conversion)

Summary

Converts a raster dataset to an ASCII 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 ...

  NODATA_VALUE in the example above 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 Copy Raster tool also supports the origin as the center of the lower left cell.

• At ArcGIS AllSource 3.2 and later, the default tool output is an ASCII file with an .asc extension, not a .txt extension. For existing ASCII files with a .txt extension, renaming the file using the .asc extension is recommended.

Parameters

Dialog

Label	Explanation	Data Type
Input raster	The input raster dataset. The raster can be integer or floating-point type.	Raster Layer
Output ASCII raster file	The output ASCII raster file.	File

Python

arcpy.conversion.RasterToASCII(in_raster, out_ascii_file)

Name	Explanation	Data 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 1 (Python window)

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

import arcpy
arcpy.env.workspace = "c:/data"
arcpy.conversion.RasterToASCII("elevation", "c:/output/sa500.asc")

RasterToASCII example 2 (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

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

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

# Run RasterToASCII
arcpy.conversion.RasterToASCII(inRaster, outASCII)

Environments

Auto Commit, Cell Size, Cell Size Projection Method, Current Workspace, Extent, Geographic Transformations, Output CONFIG Keyword, Output Coordinate System, Scratch Workspace