Polygon to polygon spatial join but not using Spatial Join

ChrisMathers — Fri, 01 Jun 2012 19:18:43 GMT

There must be a better way to do this. I am joining a parcel feature class to flood zones and to surge zones. I do not like that with a spatial join if two join features with the same code both intersect a parcel the parcel will have duplicate values, i.e. '1,2,1,1,3.' Below is the way I figured to do it but with two selections and a calculation per iteration Im looking at about 8 minutes per iteration. Except flood zone X and surge zone 1, those are about 33 minutes and 17 minutes respectively. The reason I do it this way is so the formatting is nice looking in the field. The only other way I can think of is to do a spatial join and then cursor over the field splitting the value into a list, making the list a set, sorting the set and then writing it back to the field. Due to field length some values might get truncated during the spatial join and be lost. I dont have a time on doing it that way but I cant imagine it would be too much more efficient.

                    arcpy.MakeFeatureLayer_management(r'\\Bay-gis\GIS Staff\Parcel_Processor\OSA@sde@bay-gis.sde\sde.SDE.ReferencedData\sde.SDE.Flood_Zones_2009','FloodZones','FLD_ZONE <> \'0.2 PCT ANNUAL CHANCE FLOOD HAZARD\' AND FLD_ZONE <> \'OPEN WATER\'')
                    for zone in ['A','AE','VE','X']:
                        query="FLD_ZONE = '%s'"%zone
                        arcpy.SelectLayerByAttribute_management('FloodZones','NEW_SELECTION',query)
                        arcpy.SelectLayerByLocation_management('parcels','INTERSECT','FloodZones')
                        cursor=arcpy.UpdateCursor('parcels')
                        for row in cursor:
                            if row.Flood_zn==None:
                                row.Flood_zn=zone
                            else:
                                row.Flood_zn=row.Flood_zn+',%s'%zone
                            cursor.updateRow(row)
                        del cursor

                    arcpy.MakeFeatureLayer_management(r'\\Bay-gis\GIS Staff\Parcel_Processor\OSA@sde@bay-gis.sde\sde.SDE.ReferencedData\sde.SDE.Storm_Surge','StormSurge')
                    for zone in ['1','2','3','4','5']:
                        query="Cat = '%s'"%zone
                        arcpy.SelectLayerByAttribute_management('StormSurge','NEW_SELECTION',query)
                        arcpy.SelectLayerByLocation_management('parcels','INTERSECT','StormSurge')
                        cursor=arcpy.UpdateCursor('parcels')
                        for row in cursor:
                            if row.Surge==None:
                                row.Surge=zone
                            else:
                                row.Surge=row.Surge+',%s'%zone
                            cursor.updateRow(row)
                        del cursor

Re: Polygon to polygon spatial join but not using Spatial Join

markdenil — Mon, 04 Jun 2012 11:07:26 GMT

Why not just intersect the parcels with the flood zones and surge zones, and sort out the field values from the resulting fc?
That way, you only interstect once.
Running a search cursor through the result fc once, you could, say, build a dictionary for each parcel of the intersected zones.
Then use that dictionary to update the parcel values.

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Polygon to polygon spatial join but not using Spatial Join

Re: Polygon to polygon spatial join but not using Spatial Join