Contour (Spatial Analyst)
Summary
Creates a line feature class of contours (isolines) from a raster surface.
Usage
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Contours do not extend beyond the spatial extent of the raster, and they are not generated in areas of NoData; therefore, adjacent contour inputs should first be edgematched into a continuous feature dataset. As an alternative to edgematching, you can merge the adjacent rasters before computing contours.
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Contours can be generated in areas of negative raster values. The contour values will be negative in such areas. Negative contour intervals are not allowed.
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Smoother but less accurate contours can be obtained by pre-processing the input raster with a Focal_Statistics operation with the MEAN option or the Filter tool with the LOW option.
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A base contour is used, for example, when you want to create contours every 15 meters, starting at 10 meters. Here, 10 would be used for the base contour, and 15 would be the contour interval. The values to be contoured would be 10, 25, 40, 55, and so on.
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Specifying a base contour does not prevent contours from being created above or below that value.
Syntax
| Parameter | Explanation | Data Type |
in_raster |
The input surface raster. | Raster Layer |
out_polyline_features |
Output contour polyline features. | Feature Class |
contour_interval | Interval of contours. This can be any positive number. | Double |
base_contour (Optional) |
Base contour value. Contours are generated above and below this value as needed to cover the entire value range of the input raster. The default is zero. | Double |
z_factor (Optional) |
Number of ground x,y units in one surface z unit. The z-factor adjusts the units of measure for the z units when they are different from the x,y units of the input surface. The z-values of the input surface are multiplied by the z-factor when calculating the final output surface. If the x,y units and z units are in the same units of measure, the z-factor is 1. This is the default. If the x,y units and z units are in different units of measure, the z-factor must be set to the appropriate factor, or the results will be incorrect. For example, if your z units are feet and your x,y units are meters, you would use a z-factor of 0.3048 to convert your z units from feet to meters (1 foot = 0.3048 meter). | Double |
Code Sample
This example creates contours from an ESRI GRID raster and outputs them as a shapefile.
import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
Contour("elevation", "C:/sapyexamples/output/outcontours.shp", 200, 0)
This example creates contours from an ESRI GRID raster and outputs them as a shapefile.
# Name: Contour_Ex_02.py
# Description: Creates contours or isolines from a raster surface.
# Requirements: Spatial Analyst Extension
# Author: ESRI
# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *
# Set environment settings
env.workspace = "C:/sapyexamples/data"
# Set local variables
inRaster = "elevation"
contourInterval = 200
baseContour = 0
outContours = "C:/sapyexamples/output/outcontours02.shp"
# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")
# Execute Contour
Contour(inRaster, outContours, contourInterval, baseContour)