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SpatialReference

In this topic

  1. Summary
  2. Discussion
  3. Syntax
  4. Properties
  5. Method Overview
  6. Methods
  7. Code sample
Related topics
  1. Use classes in Python
  2. Using the spatial reference class

Summary

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

Discussion

A SpatialReference object can also be accessed from existing datasets using the Describe spatialReference property.

dataset = "c:/data/landbase.gdb/Wetlands"
spatial_ref = arcpy.Describe(dataset).spatialReference

XY, Z, and M extents are not the same as spatial reference domains. The XY, Z, and M domains in a spatial reference define the valid range of coordinate values that can be stored in a feature class. The feature class extents reflect the actual range of coordinate values that exist in the feature class. These extents cannot be larger than the domains.

The SpatialReference object supports equal (==) and not equal (!=) operators for comparing spatial references.

Note:

The spatial reference properties available depend on the coordinate system used. In the properties list below, those properties that are only available with a projected coordinate system are denoted with a 1; properties only available with a geographic coordinate system are denoted with a 2.

Because a projected coordinate system is based on a geographic coordinate system, projected coordinate system properties can be accessed from a geographic coordinate system using the GCS property.

Syntax

 SpatialReference ({item}, {vcs}, text)
ParameterExplanationData Type
item

The horizontal coordinate system used to create the SpatialReference. The coordinate system can be set using a projection file, name, or factory code.

  • Using the display name of the coordinate system
    sr = arcpy.SpatialReference("Sinusoidal (world)")
  • Using the canonical name of the coordinate system
    sr = arcpy.SpatialReference("World_Sinusoidal")
  • Using a coordinate system's factory code (or authority code or WKID)
    # The factory code of 32145 represents: 
# NAD 1983 StatePlane Vermont FIPS 4400 (Meters)

sr = arcpy.SpatialReference(32145)
  • Using a projection file (.prj)
    sr = arcpy.SpatialReference("c:/coordsystems/NAD 1983.prj")

For more information about coordinate system names and factory codes, see the geographic_coordinate_systems.pdf and projected_coordinate_systems.pdf files.

For more information, see Using the spatial reference class.

Variant
vcs

The vertical coordinate system (VCS). The VCS defines information about the z-coordinates, and can be set using a name or factory code. See the following examples:

  • Using a name
    sr = arcpy.SpatialReference("Hawaii Albers Equal Area Conic", "MSL Height")
  • Using a factory code
    
# Spatial Reference factory code of 32145 is : NAD 1983 StatePlane Vermont FIPS 4400 (Meters)
# Spatial Reference factory code of 5714 is : Mean Sea Level (Height)

sr = arcpy.SpatialReference(32145, 5714)
Variant
text

A well-known text (WKT) string that can be used to define a horizontal and vertical coordinate system.

  • Using a WKT string with a horizontal coordinate system
    # String below is the WKT for the 
# Geographic Coordinate system "WGS 1984" (factory code=4326)
wkt = "GEOGCS['GCS_WGS_1984',DATUM['D_WGS_1984',SPHEROID['WGS_1984',6378137.0,298.257223563]],\
              PRIMEM['Greenwich',0.0],UNIT['Degree',0.0174532925199433]];\
              -400 -400 1000000000;-100000 10000;-100000 10000;8.98315284119522E-09;\
              0.001;0.001;IsHighPrecision"

sr = arcpy.SpatialReference(text=wkt)
  • Using a WKT string with a horizontal and vertical coordinate system. Note that the vcs argument is not used, and the vertical coordinate system is defined in the VERTCS section of the WKT.
    # The following string is the WKT for the 
# Geographic Coordinate system "WGS 1984" (factory code=4326)
wkt = "GEOGCS['GCS_WGS_1984',DATUM['D_WGS_1984',SPHEROID['WGS_1984',6378137.0,298.257223563]],\
              PRIMEM['Greenwich',0.0],UNIT['Degree',0.0174532925199433]],\
              VERTCS['WGS_1984',DATUM['D_WGS_1984',SPHEROID['WGS_1984',6378137.0,298.257223563]],\
              PARAMETER['Vertical_Shift',0.0],PARAMETER['Direction',1.0],UNIT['Meter',1.0]];\
              -400 -400 1000000000;-100000 10000;-100000 10000;8.98315284119522E-09;\
              0.001;0.001;IsHighPrecision"

sr = arcpy.SpatialReference(text=wkt)
String

Properties

PropertyExplanationData Type
GCS
(Read Only)

A projected coordinate system returns a SpatialReference object for the geographic coordinate system it is based on. A geographic coordinate system returns the same SpatialReference.

SpatialReference
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
VCS
(Read Only)

If the coordinate system has a vertical coordinate system, it returns a VCS object for the vertical coordinate system it is based on.

Object
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 or well-known ID (WKID) of the spatial reference.

Integer
falseOriginAndUnits
(Read Only)

The false origin and units.

String
hasMPrecision
(Read Only)

Indicates whether m-value precision information has been defined.

Boolean
hasXYPrecision
(Read Only)

Indicates whether xy precision information has been defined.

Boolean
hasZPrecision
(Read Only)

Indicates whether z-value precision information has been defined.

Boolean
isHighPrecision
(Read and Write)

Indicates whether 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.

  • Geographic—A geographic coordinate system.
  • Projected— A projected coordinate system.
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
latitudeOfOrigin
(Read and Write)

The latitude of origin 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
longitude
(Read and Write)

The longitude value of this prime meridian.1

Double
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
metersPerUnit
(Read Only)

The meters per linear unit.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 SpatialReference object using properties.

createFromFile (prj_file)

Creates the SpatialReference object from a projection file.

exportToString ()

Exports the object to its string representation.

loadFromString (string)

Defines a SpatialReference object from a WKT string.

The exportToString method can be used to export a WKT string representation of the spatial reference.

  • Using a WKT string with a horizontal coordinate system.
    # The following string is the WKT for the 
# Geographic Coordinate system "WGS 1984" (factory code=4326)
wkt = 'GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],\
              PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]];\
              -400 -400 1000000000;-100000 10000;-100000 10000;8.98315284119522E-09;\
              0.001;0.001;IsHighPrecision'

sr = arcpy.SpatialReference()
sr.loadFromString(wkt)
  • Using a WKT string with a horizontal and vertical coordinate system. Note that the vertical coordinate system is defined in the VERTCS section of the WKT.
    # The following string is the WKT for the 
# Geographic Coordinate system "WGS 1984" (factory code=4326), 
# with a vertical coordinate system "WGS 1984" (factory code=115700)

wkt = 'GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],\
              PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],\
              VERTCS["WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],\
              PARAMETER["Vertical_Shift",0.0],PARAMETER["Direction",1.0],UNIT["Meter",1.0]];\
              -400 -400 1000000000;-100000 10000;-100000 10000;8.98315284119522E-09;\
              0.001;0.001;IsHighPrecision'

sr = arcpy.SpatialReference()
sr.loadFromString(wkt)

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.

setMFalseOriginAndUnits (false_m, m_units)

Sets the M false origin and units.

setZDomain (z_min, z_max)

Sets the Z domain.

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 SpatialReference object.

String
exportToString ()
Return Value
Data TypeExplanation
String

The WKT string representation of the object. 

loadFromString (string)
ParameterExplanationData Type
string

The WKT 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
setMFalseOriginAndUnits (false_m, m_units)
ParameterExplanationData Type
false_m

The false m-value.

Double
m_units

The m units.

Double
setZDomain (z_min, z_max)
ParameterExplanationData Type
z_min

The minimum z-value.

Double
z_max

The maximum z-value.

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

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

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

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

    # If the spatial reference is unknown
    if spatial_ref.name == "Unknown":
        print("{} has an unknown spatial reference".format(fc))

    # Otherwise, print out the feature class name and spatial reference
    else:
        print("{} : {}".format(fc, spatial_ref.name))

Related topics

  • Use classes in Python
  • Using the spatial reference class

Feedback on this topic?

In this topic
  1. Summary
  2. Discussion
  3. Syntax
  4. Properties
  5. Method Overview
  6. Methods
  7. Code sample
Related topics
  1. Use classes in Python
  2. Using the spatial reference class