Latest Contributions by DudleyMcFadden

Have you created indices on the attributes participating in the join?  (ArcToolbox, Data Management Tools, Indexes, Add Attribute Index).  I don't think shapefiles and file geodatabases support multiple indices directly, but it still might help. ... View more

I learned a couple of things since my prior post. The NAD 1983 California (Teale) Albers (US Feet) entry in ArcGIS is indeed wrong.  The False Northing was entered incorrectly back in ArcGIS 9.2 or so.  The definition in terms of meters is correct. If you use Python, the arcpy.DefineProjection_management tool can be used to record a change to the assigned coordinate system into a feature class.  But you must specify the False Northing parameter in meters.  The tool will convert this value before assigning the coordinate system to the feature class.  The parameters used in arcpy script tool are in different units from what are later reported when you query the coordinate system. The California Albers coordinate system should have a false northing of –4,000,000 meters.  That converts to -13,123,333.333 feet.  Make sure you specify this and verify it.  Especially if you're working with dam failure inundation maps in HEC-RAS for the state of California's Division of Safety of Dams. ... View more

I too have just come across this issue when working with data touched by HEC-RAS, and, perhaps not coincidentally, with California dam failure inundation maps.  But I do wonder if this is actually stemming from incorrect projection definitions bundled with ArcGIS. Consider a similar case:  the state of Wisconsin's preferred projection.  It's right above California's Teale Albers projections in the coordinate system list in ArcGIS.  Have a look at the False Easting and False Northing values for: NAD 1983 (2011) Wisconsin TM (Meters) NAD 1983 (2011) Wisconsin TM (US Feet) Click between the two of them several times.  You will see that the False Easting and False Northing parameters are different between them.  I didn't break out a calculator to verify but they sure look like they're different by a factor of, oh, 3.28 or so. Now go down the list and have a look at the False Easting and False Northing parameters for: NAD 1983 California (Teale) Albers (Meters) NAD 1983 California (Teale) Albers (US Feet) Again, click between the two of them several times.  You will see that the False Easting and False Northing parameters are the same between them.  (Well, see the easting is 0, so of course multiplying it by any factor would make it be the same, but the northing is also the same between them, a nice round number, minus four million). So apparently the False Easting is supposed to be specified in the linear units of the projection.  Somebody at either ESRI or the US Army Corps of Engineers (the folks behind HEC-RAS), or the European Petroleum Survey Group (EPSG) misunderstood the measurement units required for these parameters in the projection. ... View more