[GIS] Checking whether Spatial Reference is Projected Coordinate System using ArcPy

arcgis-10.1arcpycoordinate systemvector-grid

I'm modifying CreateFishnet in ArcGIS 10.1 using python.. I want to ask the user to input a projected coordinate as spatial reference.

How can I check if the user didn't put geographic coordinate by mistake?

I have one idea that,i will ask the user to put WKID as reference to input coordinate. In that case I can check whether that is a projected coordinate.
But, if i make a tool with that script, i can use GetParamterAsText function and set the value as 'spatial referecne'. In this case, user will select coordinate from Geographic/Projected coordinate folder.

How can I make sure that a projected coordinate is chosen in this case?

Best Answer

To determine whether an arcpy SpatialReference object is projected or geographic use the property type:

geoSR = arcpy.SpatialReference(4326)
print geoSR.type
Geographic

projSR = arcpy.SpatialReference(28356)
print projSR.type
Projected

Related Solutions

Coordinate System – Determining if Spatial Reference is Geographic or Projected Using ArcObjects

You can check the object type like so:

ISpatialReference ref = ...; // This is your spatial reference
if (ref is IGeographicCoordinateSystem) {
    //Geographic
} else if (ref is IProjectedCoordinateSystem) {
    // Projected
} else {
    // Unknown coordinate system
}

ArcGIS Desktop – Describing a Coordinate System in Arcpy

Two possible solutions I've found in playing around with the SpatialReference class:

In your script tool parameter's dialog, change the data type of the Coordinate System parameter to Spatial Reference. A spatial reference contains a bit more information than a coordinate system and is what is expected by GetParameter if you're expecting it to create a SpatialReference object.
- Note: In my testing this only works when run as a script tool, not as a standalone Python script, presumably because GetParameter requires the script tool parameter definitions to infer what type of object to create from the input string.
In addition to the above change, you can use the SpatialReference.loadFromString() method to create a spatial reference object from its string representation explicitly. This should work both within a script tool and a standalone Python script. E.g.:
```
import arcpy
input1 = arcpy.GetParameterAsText(0)
input2 = arcpy.GetParameterAsText(1)
srtxt = arcpy.GetParameterAsText(2)
sr = arcpy.SpatialReference()
sr.loadFromString(srtxt)
if not sr.type == "Projected":
    raise RuntimeError("Input coordinate system is not projected.")
```
You'll note I also changed the coordinate system type checking to be more explicit and changed the error handling logic to raise an error which is a bit more Pythonic, though you are free to handle it how you want.

Best Answer

Related Solutions

Coordinate System – Determining if Spatial Reference is Geographic or Projected Using ArcObjects

ArcGIS Desktop – Describing a Coordinate System in Arcpy

Related Question