CA State Plane to CA Teale Albers converts false northing ft-->m

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08-29-2018 05:10 PM
PeterKulchawik
New Contributor

I have a raster in NAD83 CA State Plane Zone II (US feet) that I need to project to NAD83 CA Teale Albers (US feet).  When I run the project raster tool, the false northing on the output raster changes from -4,000,000 (what it should be per the .prj file) to -13,123,333.3333.  The difference between the two numbers is a factor of 3.28 so my guess this is a feet to meters issue.  

The values of the original raster (the one in SP) are in feet.  The spatial reference properties are:
Spatial reference: NAD_1983_StatePlane_California_II_FIPS_0402_Feet
Linear Unit: Foot_US (0.304801)
Angular Unit: Degree (0.0174532925199433)
false_easting: 6561666.666666666
false_northing: 1640416.666666667
central_meridian: -122
standard_parallel_1: 38.33333333333334
standard_parallel_2: 39.83333333333334
latitude_of_origin: 37.66666666666666
Datum: D_North_American_1983

The spatial reference properties that the projected raster SHOULD have:
Spatial reference: NAD_1983_California_Teale_Albers_FtUS
Linear Unit: Foot_US (0.304801)
Angular Unit: Degree (0.0174532925199433)
false_easting: 0
false_northing: -4000000
central_meridian: -120
standard_parallel_1: 34
standard_parallel_2: 40.5
latitude_of_origin: 0
Datum: D_North_American_1983

When I run the tool on the original raster, the spatial reference properties that the raster ends up having:
Spatial reference: NAD_1983_California_Teale_Albers_FtUS
Linear Unit: Foot_US (0.304801)
Angular Unit: Degree (0.0174532925199433)
false_easting: 0
false_northing: -13123333.33333333
central_meridian: -120
standard_parallel_1: 34
standard_parallel_2: 40.5
latitude_of_origin: 0
Datum: D_North_American_1983

The resulting raster ends up somewhere in northern Canada.  Certainly no offense to Canada, but I need my data to be in Sonoma County. Any ideas on why -4000000 is being converted to -13123333.3333? 

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11 Replies
DudleyMcFadden
New Contributor II

I learned a couple of things since my prior post.

  1. 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.
  2. 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.

EricAnderson
New Contributor II

I found this from Melita Kennedy.   The false northings for the foot version of Teale Albers was incorrectly defined in the projection parameters.  However, behind the scenes it appears to be ok.  https://gis.stackexchange.com/questions/343820/is-the-esri-arcgis-definition-of-california-albers-pr...