SpatialReference

Summary

Each part of the spatial reference has a number of properties, especially the coordinate system, which defines what map projection options are used to define horizontal coordinates.

Discussion

A SpatialReference can be easily created from existing datasets and PRJ files:

  1. Use a PRJ file as an argument to the SpatialReference class.
    import arcpy, os
prjFile = os.path.join(arcpy.GetInstallInfo()["InstallDir"],
                       "Coordinate Systems/Geographic Coordinate Systems/North America/NAD 1983.prj")
spatialRef = arcpy.SpatialReference(prjFile)
  2. Describe a dataset and access its spatialReference property.
    dataset = "C:/Data/Landbase.gdb/Wetlands"
spatialRef = arcpy.Describe(dataset).spatialReference
NoteNote:

Which spatial reference properties are available depends on the coordinate system used. In the properties list below, those properties only available with a Projected Coordinate system are denoted with a 1; properties available only with a Geographic Coordinate system are denoted with a 2.

Syntax

SpatialReference (prjFile)
ParameterExplanationData Type
prjFile

The projection file used to populate the spatial reference object.

String

Properties

PropertyExplanationData Type
MDomain
(Read Only)

The extent of the measure domain.

String
MFalseOriginAndUnits
(Read Only)

The measure false origin and units.

String
MResolution
(Read and Write)

The measure resolution.

Double
MTolerance
(Read and Write)

The measure tolerance.

Double
XYResolution
(Read and Write)

The xy resolution.

Double
XYTolerance
(Read and Write)

The xy tolerance.

Double
ZDomain
(Read Only)

The extent of the Z domain.

String
ZFalseOriginAndUnits
(Read Only)

The Z false origin and units.

String
ZResolution
(Read and Write)

The Z resolution property.

Double
ZTolerance
(Read and Write)

The Z tolerance property.

Double
abbreviation
(Read and Write)

The abbreviated name of the spatial reference.

String
alias
(Read and Write)

The alias of the spatial reference.

String
domain
(Read Only)

The extent of the xy domain.

String
factoryCode
(Read and Write)

The factory code of the spatial reference.

Integer
falseOriginAndUnits
(Read Only)

The false origin and units.

String
hasMPrecision
(Read Only)

Indicates whether or not m-value precision information has been defined.

Boolean
hasXYPrecision
(Read Only)

Indicates whether or not xy precision information has been defined.

Boolean
hasZPrecision
(Read Only)

Indicates whether or not z-value precision information has been defined.

Boolean
isHighPrecision
(Read and Write)

Indicates whether or not the spatial reference has high precision set.

Boolean
name
(Read and Write)

The name of the spatial reference.

String
remarks
(Read and Write)

The comment string of the spatial reference.

String
type
(Read and Write)

The type of the spatial reference.

String
usage
(Read Only)

The usage notes.

String
PCSCode
(Read and Write)

The projected coordinate system code.1

Integer
PCSName
(Read and Write)

The projected coordinate system name.1

String
azimuth
(Read and Write)

The azimuth of a projected coordinate system.1

Double
centralMeridian
(Read and Write)

The central meridian of a projected coordinate system.1

Double
centralMeridianInDegrees
(Read and Write)

The central meridian (Lambda0) of a projected coordinate system in degrees.1

Double
centralParallel
(Read and Write)

The central parallel of a projected coordinate system.1

Double
classification
(Read Only)

The classification of a map projection.1

String
falseEasting
(Read and Write)

The false easting of a projected coordinate system.1

Double
falseNorthing
(Read and Write)

The false northing of a projected coordinate system.1

Double
latitudeOf1st
(Read and Write)

The latitude of the first point of a projected coordinate system.1

Double
latitudeOf2nd
(Read and Write)

The latitude of the second point of a projected coordinate system.1

Double
linearUnitCode
(Read and Write)

The linear unit code.1

Integer
linearUnitName
(Read and Write)

The linear unit name.1

String
longitudeOf1st
(Read and Write)

The longitude of the first point of a projected coordinate system.1

Double
longitudeOf2nd
(Read and Write)

The longitude of the second point of a projected coordinate system.1

Double
longitudeOfOrigin
(Read and Write)

The longitude of origin of a projected coordinate system.1

Double
projectionCode
(Read and Write)

The projection code.1

Integer
projectionName
(Read and Write)

The projection name.1

String
scaleFactor
(Read and Write)

The scale factor of a projected coordinate system.1

Double
standardParallel1
(Read and Write)

The first parallel of a projected coordinate system.1

Double
standardParallel2
(Read and Write)

The second parallel of a projected coordinate system.1

Double
GCSCode
(Read and Write)

The geographic coordinate system code.2

Integer
GCSName
(Read and Write)

The geographic coordinate system name.2

String
angularUnitCode
(Read and Write)

The angular unit code.2

Integer
angularUnitName
(Read and Write)

The angular unit name.2

String
datumCode
(Read and Write)

The datum code.2

Integer
datumName
(Read and Write)

The datum name.2

String
flattening
(Read and Write)

The flattening ratio of this spheroid.2

Double
longitude
(Read and Write)

The longitude value of this prime meridian.2

Double
primeMeridianCode
(Read and Write)

The prime meridian code.2

Integer
primeMeridianName
(Read and Write)

The prime meridian name.2

String
radiansPerUnit
(Read Only)

The radians per angular unit.2

Double
semiMajorAxis
(Read and Write)

The semi-major axis length of this spheroid.2

Double
semiMinorAxis
(Read and Write)

The semi-minor axis length of this spheroid.2

Double
spheroidCode
(Read and Write)

The spheroid code.2

Integer
spheroidName
(Read and Write)

The spheroid name.2

String

Method Overview

MethodExplanation
create ()

Creates the spatial reference object using properties.

createFromFile (prj_file)

Creates the spatial reference object from a projection file.

exportToString ()

Exports the object to its string representation.

loadFromString (string)

Restore the object using its string representation. The exportToString method can be used to create a string representation.

setDomain (x_min, x_max, y_min, y_max)

Sets the XY domain.

setFalseOriginAndUnits (false_x, false_y, xy_units)

Sets the XY false origin and units.

setMDomain (m_min, m_max)

Sets the M domain.

setZDomain (z_min, z_max)

Sets the Z domain.

setMFalseOriginAndUnits (false_m, m_units)

Sets the M false origin and units.

setZFalseOriginAndUnits (false_z, z_units)

Sets the Z false origin and units.

Methods

create ()
createFromFile (prj_file)
ParameterExplanationData Type
prj_file

The projection file used to populate the spatial reference object.

String
exportToString ()
Return Value
Data TypeExplanation
String

The string representation of the object.

loadFromString (string)
ParameterExplanationData Type
string

The string representation of the object.

String
setDomain (x_min, x_max, y_min, y_max)
ParameterExplanationData Type
x_min

The minimum x-value.

Double
x_max

The maximum x-value.

Double
y_min

The minimum y-value.

Double
y_max

The maximum y-value.

Double
setFalseOriginAndUnits (false_x, false_y, xy_units)
ParameterExplanationData Type
false_x

The false x value.

Double
false_y

The false y value.

Double
xy_units

The xy units.

String
setMDomain (m_min, m_max)
ParameterExplanationData Type
m_min

The minimum m-value.

Double
m_max

The maximum m-value.

Double
setZDomain (z_min, z_max)
ParameterExplanationData Type
z_min

The minimum z-value.

Double
z_max

The maximum z-value.

Double
setMFalseOriginAndUnits (false_m, m_units)
ParameterExplanationData Type
false_m

The false m-value.

Double
m_units

The m units.

Double
setZFalseOriginAndUnits (false_z, z_units)
ParameterExplanationData Type
false_z

The false z-value.

Double
z_units

The false z units.

Double

Code Sample

SpatialReference example

For each feature class in a workspace, print the name of its spatial reference.

import arcpy
from arcpy import env

# Set the workspace environment
#
env.workspace = "C:/base/base.gdb"

# Get a list of the feature classes in the input folder
#
fcs = arcpy.ListFeatureClasses()

# Loop through the list
#
for fc in fcs:
    # Create the spatial reference object
    #
    sr = arcpy.Describe(fc).spatialReference

    # If the spatial reference is unknown
    #
    if sr.name == "Unknown":
        print fc + " has an unknown spatial reference\n"

    # Otherwise, print out the feature class name and
    #   spatial reference
    #
    else:
        print fc + ": " + sr.name + "\n"
SpatialReference example 2

Create a SpatialReference using a .prj file.

import arcpy

prjFile = "c:/Program Files/ArcGIS/Desktop10.0/Coordinate Systems/Projected Coordinate Systems" + \
           "/Continental/North America/USA Contiguous Equidistant Conic.prj"

# Create a spatial reference object using a projection file
#
sr = arcpy.SpatialReference(prjFile)
SpatialReference example 3

Create a SpatialReference from a factory code.

import arcpy

# Create a spatial reference object using a factory code
#
sr = arcpy.SpatialReference()
sr.factoryCode = 3857
sr.create()

Related Topics

Using classes in Python

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10/28/2011