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PathDistance Calculation discrepancy

AlexanderKeyel

I am updating an ArcGIS toolbox from ArcGIS 9.3 to ArcGIS 10.3. The tools "gp.PathDistance_sa" and "arcpy.sa.PathDistance" produce different outputs using the same input settings and input layers. Is there any documentation for changes to this tool? Any idea regarding the cause of the discrepancy?

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AlexanderKeyel

To the best of my abilities, I am doing everything the same.

We are using the exact same input files. If I replace the Viewshed and PathDistance outputs from ArcGis 10.3 with the Arc 9.3 versions, I can get the exact same final output out to ~3 to 5 decimal places. See https://community.esri.com/message/586624?et=watches.email.thread#586624 for the similar problem with the viewshed tool.

For environments, we've replaced:

### Set general parameters for rasters

dscRD = gp.Describe(eucdist_ft)

RasterExtent = dscRD.Extent

CellSize = dscRD.MeanCellHeight

with:

# Set general parameters for rasters

dscRD = arcpy.Describe(eucdist_ft)

RasterExtent = dscRD.Extent

CellSize = dscRD.MeanCellHeight

and in the applicable tools we have replaced:

### Environment settings

##gp.Extent = RasterExtent

##gp.CellSize = CellSize

with:

arcpy.env.extent = RasterExtent

arcpy.env.cellSize = CellSize

We had not set snap raster but I just added it in both the 9.3 code and the 10.3 code, and the major differences between versions persist.

DanPatterson_Retired

and to clarify, you are doing this with the exact same files, the same environment settings (in the Environments section for the tool ie extent, cell size, snap raster etc, not the general settings for arc*)?

AlexanderKeyel

I read the help section for both tools, and did not see any indication that the algorithm had changed. I was also unsuccessful in finding anything with Google, nor through consultation with our local GIS center. However, I am getting differences in output of around 0.5, which in the system I'm working in, is high enough that it's worth trying to find an explanation for the discrepancy.

DarrenWiens2

A quick scan of the helps (9.3 vs. 10.3) look like they use the same algorithm, but you should do a thorough look-through, if you haven't.

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