topic Re: Issues with ArcPy SpatialReference Class in Python Questions

Issues with ArcPy SpatialReference Class

MattBrehm — Wed, 27 Apr 2016 08:34:15 GMT

I am attempting to write a Python script that uses a general reference map of the NAD 1983 UTM Zones to automate the selection of an appropriate map projection for a specific area. I have completed the script up until the point at which I need to create a SpatialReference object that contains the appropriate projection. I have been getting a 999999 general runtime error whenever I try to assign the SpatialReference object the value of "NAD 1983 UTM Zone 9N" or lower, but past "NAD 1983 UTM Zone 10N", it works.

This screenshot is the result of a test script in which I import ArcPy, and then try to initialize a SpatialReference object with the respective values mentioned above. In the second run, I printed the SpatialReference object's name in order to test to make sure that the value was assigned correctly. Am I missing something here, or is this a known issue with assigning the names of projections to SpatialReference objects? I would otherwise use the WKID for the projection, but the reference map that I am using only contains a field for the name of the projection.

Edit: I am using general reference maps for both the NAD 1983 UTM Zones as well as the USA State Plane Zones NAD83 in order to find an appropriate projection for an input dataset. I first find the centroid of the dataset, and then select by location from the reference projection maps. From the responses here and my own testing, it seems as if trying to assign SpatialReference objects the projections by name does not work for certain types of projections. Namely, the NAD 1983 UTM Zone 1-9 projections. I have also yet to find a U.S. State Plane projection in which the SpatialReference object does not give an error when attempting to assign the projection by name. The solution seems to be to assign the SpatialReference object by WKID. but this could be quite cumbersome if the assignment of projection WKIDs does not follow an intuitive pattern and you're working with hundreds of reference projections.

Re: Issues with ArcPy SpatialReference Class

DanPatterson_Retired — Wed, 27 Apr 2016 09:27:44 GMT

I have a vague recollection of something... try putting an r in front of the coordinate reference ie r"NAD....." but I remember something about underscores, but I can't put my hands on it.

Re: Issues with ArcPy SpatialReference Class

NeilAyres — Wed, 27 Apr 2016 09:57:31 GMT

Why not just use the WKID to reference the correct zone.

NAD83 UTM xxN is numbered very logically

NAD_1983_UTM_Zone_1N 26901

NAD_1983_UTM_Zone_2N 26902

...

NAD_1983_UTM_Zone_10N 26910

etc

Re: Issues with ArcPy SpatialReference Class

DanPatterson_Retired — Wed, 27 Apr 2016 10:04:23 GMT

his last sentence says why

Re: Issues with ArcPy SpatialReference Class

NeilAyres — Sat, 11 Dec 2021 16:33:00 GMT

You could just create it on the fly.

A quick investigation...

>>> import arcpy
>>> idList = [str(i+1).zfill(2) for i in range(0, 50)]
>>> idList
['01', '02', '03', '04', '05', '06', '07', '08', '09', '10', '11', '12', '13', '14', '15', '16', '17', '18', '19', '20', '21', '22', '23', '24', '25', '26', '27', '28', '29', '30', '31', '32', '33', '34', '35', '36', '37', '38', '39', '40', '41', '42', '43', '44', '45', '46', '47', '48', '49', '50']
>>> base = "269"
>>> for i in idList:
 sr = arcpy.SpatialReference(int(base + i))
 name = sr.name
 print "WKID {}  Name {}".format(int(base + i), name)

WKID 26901  Name NAD_1983_UTM_Zone_1N
WKID 26902  Name NAD_1983_UTM_Zone_2N
WKID 26903  Name NAD_1983_UTM_Zone_3N
WKID 26904  Name NAD_1983_UTM_Zone_4N
WKID 26905  Name NAD_1983_UTM_Zone_5N
WKID 26906  Name NAD_1983_UTM_Zone_6N
WKID 26907  Name NAD_1983_UTM_Zone_7N
WKID 26908  Name NAD_1983_UTM_Zone_8N
WKID 26909  Name NAD_1983_UTM_Zone_9N
WKID 26910  Name NAD_1983_UTM_Zone_10N
WKID 26911  Name NAD_1983_UTM_Zone_11N
WKID 26912  Name NAD_1983_UTM_Zone_12N
WKID 26913  Name NAD_1983_UTM_Zone_13N
WKID 26914  Name NAD_1983_UTM_Zone_14N
WKID 26915  Name NAD_1983_UTM_Zone_15N
WKID 26916  Name NAD_1983_UTM_Zone_16N
WKID 26917  Name NAD_1983_UTM_Zone_17N
WKID 26918  Name NAD_1983_UTM_Zone_18N
WKID 26919  Name NAD_1983_UTM_Zone_19N
WKID 26920  Name NAD_1983_UTM_Zone_20N
WKID 26921  Name NAD_1983_UTM_Zone_21N
WKID 26922  Name NAD_1983_UTM_Zone_22N
WKID 26923  Name NAD_1983_UTM_Zone_23N

It errors out after 23.

Re: Issues with ArcPy SpatialReference Class

NeilAyres — Sat, 11 Dec 2021 16:33:03 GMT

This name vs wkid to specify the sr is very odd.

This wkid from my help files.

sr = arcpy.SpatialReference(102007)
>>> sr.name
u'Hawaii_Albers_Equal_Area_Conic'
>>> sr = arcpy.SpatialReference('Hawaii_Albers_Equal_Area_Conic')
Traceback (most recent call last): # errors out here, but then replace the "_" with a space
  File "<pyshell#23>", line 1, in <module>

sr = arcpy.SpatialReference('Hawaii_Albers_Equal_Area_Conic'.replace("_", " "))
>>> sr
<SpatialReference object at 0x2a68850[0x1108ead0]>
>>> sr.name
u'Hawaii_Albers_Equal_Area_Conic'

Re: Issues with ArcPy SpatialReference Class

NeilAyres — Sat, 11 Dec 2021 16:33:05 GMT

But that approach doesn't work with these UTM ids.

>>> sr = arcpy.SpatialReference(26901)
>>> sr.name
u'NAD_1983_UTM_Zone_1N'
>>> sr = arcpy.SpatialReference('NAD_1983_UTM_Zone_1N'.replace("_", " "))
Traceback (most recent call last):
  File "<pyshell#29>", line 1, in <module>
    sr = arcpy.SpatialReference('NAD_1983_UTM_Zone_1N'.replace("_", " "))
  File "C:\Program Files (x86)\ArcGIS\Desktop10.3\ArcPy\arcpy\arcobjects\mixins.py", line 949, in __init__
    self._arc_object.createFromFile(item)
RuntimeError: ERROR 999999: Error executing function.
>>>

Re: Issues with ArcPy SpatialReference Class

MattBrehm — Wed, 27 Apr 2016 16:25:32 GMT

I did try this, I know that putting an 'r' in front of a string indicates to Python to read the string as a literal, rather than reading in special characters.

i.e. Writing a string with "\n" in it will tell Python to print to the next line, etc.

I also ran a few tests with underscores vs. spaces

But unfortunately, it did not solve the issue.

Re: Issues with ArcPy SpatialReference Class

MattBrehm — Wed, 27 Apr 2016 16:27:06 GMT

It's very odd. I am not sure as to why the UTM ids don't work if the SpatialReferece object is assigned their name rather than their WKID. I was hoping to avoid creating a dictionary in Python for the UTM zones and their respective WKID numbers. I wasn't sure that they were sequential, but that will work.

Re: Issues with ArcPy SpatialReference Class

MattBrehm — Wed, 27 Apr 2016 16:39:14 GMT

It also seems to work with UTM Zones greater than 10. If you were to run your test again with the NAD 1983 UTM Zone 10N projection, it should work correctly.

Such as:

vs.

Re: Issues with ArcPy SpatialReference Class

AdrianWelsh — Wed, 27 Apr 2016 16:42:34 GMT

Matt,

From my experience of working with the SpatialReference class in Python, there are issues that have not been addressed. Certain properties that are SUPPOSED to be Read/Write are actually Read only. I had to go a complete back door approach in order to create my .prj file.

This is what I had to do:

prj = open(r"C:\junk\my_new_prj_file.prj", "w")    
crs_string = 'PROJCS["NAD_1983_UTM_Zone_10N",GEOGCS["GCS_North_American_1983",DATUM["D_North_American_1983",SPHEROID["GRS_1980",6378137,298.257222101]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",-123],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",0],UNIT["Meter",1]]'    
prj.write(crs_string)    
prj.close()

Re: Issues with ArcPy SpatialReference Class

NeilAyres — Wed, 27 Apr 2016 18:05:46 GMT

Matt,

yes this sr.name vs the "Name" you're supposed to use when trying to initiate it seems to be a bit inconsistent.

The help files refers to the pdf in the documentation installation area. But those "Names" all have underscores.

Perhaps Melita or an esri guru could explain.

Re: Issues with ArcPy SpatialReference Class

MattBrehm — Wed, 27 Apr 2016 20:47:27 GMT

Not to be insulting, but that seems like a major pain lol. It is helpful in that it shows what would go into defining the .prj file, but for just the StatePlane projections in the U.S. alone, there are 121 different features. I would not want to have to do this for all of them. I was hoping for an easy solution, but it seems as if adding a WKID field to the attribute table of the reference projection maps, adding the WKIDs for each of the projection systems, and referencing them with a SearchCursor in ArcPy is the best option for this type of workflow.

Re: Issues with ArcPy SpatialReference Class

DanPatterson_Retired — Wed, 27 Apr 2016 21:41:07 GMT

Matt... moved to Python and shared with Coordinate Reference Systems and flagging Melita Kennedy to see if a solution or commentary can be found

Re: Issues with ArcPy SpatialReference Class

AdrianWelsh — Thu, 28 Apr 2016 13:04:01 GMT

Not insulting here! It's just that this is the ONLY thing that would work for me due to me needing to creating CUSTOM projection files. If I could have used out-of-the-box projections, then utilizing the WKID would have been ideal. But, you're right, it is a major pain!

I have it more "programmatic" than just a giant string of text, though. Each of the changing variables in that string (like units, projection, scale factor, etc.) is a variable that I created earlier in the script that programmatically accesses user input so then the string looks more like this:

 projString = ('PROJCS["' + str(PIN) + '_' + ProjName +  
            '",GEOGCS[' + GeoCS +  
            '],PROJECTION["' + ProjectionName +  
            '"],PARAMETER["False_Easting",' + str(FalseEasting) +  
            '],PARAMETER["False_Northing",' + str(FalseNorthing) +  
            '],PARAMETER["Central_Meridian",' + str(CentralMeridian) +  
            '],PARAMETER["Standard_Parallel_1",' + str(StandardParallel1) +  
            '],PARAMETER["Standard_Parallel_2",' + str(StandardParallel2) +  
            '],PARAMETER["Scale_Factor",' + str(ScaleFactor) +  
            '],PARAMETER["Latitude_Of_Origin",' + str(LatOfOrigin) +  
            '],UNIT["' + LinearUnit + '",' + str(MetersPerFoot) + ']]')

But, then again, this works for me and may not be the best choice for your dataset.

Re: Issues with ArcPy SpatialReference Class

MelitaKennedy — Thu, 28 Apr 2016 16:29:09 GMT

And the answer is...

there should be two spaces between Zone and 9N. That's true of most of the NAD-based UTM zones. The name look-up that arcpy is performing isn't on the object's internal name ("NAD_1983_UTM_Zone_9N"), but on the name used for the coordinate systems "folder" structure. At the time I set them up, I didn't know that we planned to add a name look-up using them.

Melita

Re: Issues with ArcPy SpatialReference Class

DavidWasserman — Sat, 11 Dec 2021 16:33:08 GMT

I have a related question to spatial references.
I usually reference the incoming feature class or use the specific factory code for a projection.

Examples:

OutPut = arcpy.CreateFeatureclass_management(workspace, tempOutName, "POLYLINE", template=inFeatureClass,
                                                     spatial_reference=inFeatureClass)

# or

webMercatorAux = arcpy.SpatialReference(3857)

I was curious while reading this you could use either of these approaches? Is there a stability advantage? (One of my projects has some cursor instability issues ATM and I am not sure what is causing it).

Re: Issues with ArcPy SpatialReference Class

AdrianWelsh — Thu, 28 Apr 2016 16:59:55 GMT

David, I would think that either method should work fine. I personally prefer to reference in the spatial reference from an existing feature class just so I know it will keep things in the same system.

What instability issues are you seeing? Are you getting error messages?

Re: Issues with ArcPy SpatialReference Class

DavidWasserman — Thu, 28 Apr 2016 19:06:16 GMT

Hey Adrian,

I was thinking about making a post about the scripts in question it, and I don't want to hijack this one. I will tag you when I do. It has been a low priority because I got my temporary fixes to work on the projects I needed it on, but I would appreciate the input.

David

Re: Issues with ArcPy SpatialReference Class

NeilAyres — Fri, 29 Apr 2016 08:00:10 GMT

Melita,

so you are saying that if the zone number has a single digit, 2 spaces should be added to form the "Name" string.

Is that true throughout the system?

Other, non UTM style names, just the .replace("_", " ") should work?