julial

Grid has no VAT. Failed to execute Zonal Statistics error

Discussion created by julial on Feb 6, 2011
Latest reply on Feb 12, 2011 by julial
Good morning.
I want to perform a zonal statistics by table. My input zone data is a shapefile that consistis of 186,200 square polygons. Hence, I have 186, 199 FID when I open attribute table of this shape file. Delx and Dely of this shapefile are both equal to 2500 feet. It is a grid that I am using to build a groundwater model. I also have a large DEM raster (6.29 GB) that is a product of merged 71 DEm tiles. The DEM tiles that I merged had the same resolution. The resulted merged DEM raster properties are:
Rows, Columns: 52279, 32296 rows
Cell size (x,y): 9.259e-005, 9.259e-005
Pixel type: floating point
Pixel depth: 32 bit
NoData Value: -3.4028e+038

Unfortunately, performing zonal statistics on the entire domain failed.  Zonal statistics by table application ran for 7 min and 39 seconds and then stopped and  displayed the following error message : ("esriGeoAnalyst.GridEngine") Grid has no VAT. Failed to execute.(Zonal Statistics ad Table).
Performing Zonal statistics on a smaller domain (merged northwestern portion of the grid that contains 16 DEM tiles) produced the same error message (Grid has no VAT).

Just to clarify I performed the zonal statistics by defining my zone field of the feature zone data (which is my polygons grid) .
I googled the error and it appears that this "No VAT error" is a common problem when dealing with zonal stats on large ratsters. Sometimes, setting zone field to a text field equaling to a feature FID works. I tried doing that but recieved an error " Error during conversion", but the zonal stats application ran for 13 minutes this time but still failed to execute. I also tried converting my feature zone data (NFM grid) from a feature to a raster since Zonal Statistics does it internally when calculating zonal statistics. Converting my grid to a raster also resulted in error (Error in reading or opening VAT). 
Yet again, I just tried runnig a zonal statistics on a merged contiguos portion of only 3 tiles and zonal stats worked. I don't know what is the limit on the number of tiles before zonal statistics fails. Still I can't imagine that compiling zonal statistics tables from 20 or so runs of zonal stats (since it appears  that zonal stats only works on a small portion of merged tiles) will produce adequate results of average elevations.

How can I perform a zonal statistics by table on a large raster (6.29 GB) using polygons shapefile as my feature zone without getting a "NO VAT" error message. Thank you so much in advance.

JuliaL

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