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GA Layer To Contour

Available with Geostatistical Analyst license.


Creates a feature class of contours from a geostatistical layer. The output feature class can be either a line feature class of contour lines or a polygon feature class of filled contours.


  • For data formats that support Null values, such as file geodatabase feature classes, a Null value will be used to indicate that a prediction could not be made for that location or that the value should be ignored when used as input. For data formats that do not support Null values, such as shapefiles, the value of -1.7976931348623158e+308 is used (this is the negative of the C++ defined constant DBL_MAX) to indicate that a prediction could not be made for that location.

  • The output polygon or polyline features will contain slightly different geometry depending on the number of CPU cores of your machine. This is due to a different number of tiles that will be used in the contour algorithm (more cores allow for more tiling and, hence, more refined contours in the output). For reproducible results on machines with different numbers of CPU cores, use the Parallel Processing Factor environment to control the number of cores that the tool is allowed to use.

  • If the Input geostatistical layer represents a 3D interpolation model, you must specify the elevation of the contours that you want to export using the Output elevation parameter.


GALayerToContour_ga (in_geostat_layer, contour_type, out_feature_class, {contour_quality}, {classification_type}, {classes_count}, {classes_breaks}, {out_elevation})
ParameterExplanationData Type

The geostatistical layer to be analyzed.

Geostatistical Layer

Type of contour to represent the geostatistical layer.

  • CONTOUR The contour or isoline representation of the geostatistical layer. Displays the lines in either draft or presentation quality.
  • FILLED_CONTOURThe polygon representation of the geostatistical layer. It assumes for the graphical display that the values between contour lines are the same for all locations within the polygon. Displays the lines in either draft or presentation quality.
  • SAME_AS_LAYERUse the current renderer of the input geostatistical layer.

The output feature class will either be a polyline or a polygon, depending on the selected contour type.

Feature Class

Determines the smoothness of contour line representation.

  • DRAFT The default Draft quality presents a generalized version of isolines for faster display.
  • PRESENTATIONThe Presentation option ensures more detailed isolines for the output feature class.

Specifies how the contour breaks will be calculated.

  • GEOMETRIC_INTERVALContour breaks are calculated based on geometric intervals.
  • EQUAL_INTERVALContour breaks are calculated based on equal intervals.
  • QUANTILEContour breaks are calculated from quantiles of the input data.
  • MANUALSpecify your own break values.

Specify the number of classes in the output feature class.

If contour_type is set to output filled contour polygons, the number of polygons created will equal the value specified in this parameter. If it is set to output contour polylines, the number of polylines will be one less than the value specified in this parameter (because N class intervals define N-1 contour break values).

This parameter does not apply if the classification_type is set to Manual.


The list of break values if the classification_type is set to Manual. The values should be passed as a list, and the values can be in any order.

  • For contour output, these are the values of the contour lines.
  • For filled contour, these are the upper limits of each class interval. Note that if the largest break value is less than the maximum of the geostatistical layer, the output feature class will not fill up the entire rectangular extent; all locations with predicted values above the largest break will not receive filled contours.

For 3D interpolation models, you can export contours at any elevation. Use this parameter to specify the elevation that you want to export. If left empty, the elevation will be inherited from the input layer. The units will default to the same units of the input layer.

Linear Unit

Code sample

GALayerToContour interactive window example

Export a geostatistical layer to a contour feature class.

import arcpy
from arcpy import env
env.workspace = "C:/gapyexamples/data"
arcpy.GALayerToContour_ga("kriging.lyr", "Contour", "krig_contour",
                          "Presentation", "GEOMETRIC_INTERVAL", 10, "")
GALayerToContour script example

Export a geostatistical layer to a contour feature class.

# Name:
# Description: Exports a geostatistical layer to filled contours with
#              class breaks at 100, 500 and 2000.
# Requirements: Geostatistical Analyst Extension

# Import system modules
import arcpy

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

# Set local variables
in_geostat_layer = "kriging.lyr"
contour_type = "Filled_contour"
out_feature_class = "C:/gapyexamples/output/krig_filled_contour.shp"
contour_quality = "Presentation"
classification_type = "Manual"
classes_count = ""
classes_breaks = [100, 500, 2000]

# Execute GALayerToContour
arcpy.GALayerToContour_ga(in_geostat_layer, contour_type, out_feature_class,
                          contour_quality, classification_type, classes_count,

Licensing information

  • Basic: Requires Geostatistical Analyst
  • Standard: Requires Geostatistical Analyst
  • Advanced: Requires Geostatistical Analyst

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