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Hello, I am using HEC GeoRAS 4.2.92 and HEC RAS 3.1.3 to do a flood inundation mapping after I run the model in HEC RAS. I am using the tutorial "Exporting HEC-RAS Output" from the HEC-GeoRAS manual and I am following the steps outline in the tutorial. (I have tried this process 3-4 times). I am using ArcMap 9.2. Exporting an SDF file from HEC RAS model works fine. Importing an SDF file and converting it into .XML file also works in HEC GeoRas. However, when I do Layer Setup of RAS Mapping, it does not produce an .mdb with feature data but instead in the direcotry that I specify it produces an "RasOutParms.xml." In addition, "Read RAS GIS Export File" is always greyed out. Subsequently I can't make any of the "Inundation Mapping" buttons of RAS Mapping to work . I have read several post related to HEC -GeoRAS exporting/ importing issues. I have tried to use a TIN and a GRID as my DEM. Both DEM and feature classes exported from HEC RAS are in the same projection. In addition, I have tried importing a USACE original .sdf file that is used in the Baxter No Mapping example (it is available for download on the USACE website) and that also failed to produce a flood inundation map and "Read RAS GIS Export File" remained greyed out. Any help will be greatly appreciated Thank so much Julia
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05-11-2011
07:51 AM
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Good afternoon I have a polygon shapefile that I am trying to run zonal statistics on using your vert94eftfl.rtf GRID file. When running zonal statistics as table in ArcMAP 9.2 we are using our polygon shapefile as an input feature zone data and your raster file as an input value raster. Out goal is to generate an average value for each shapefile polygon using a raster file with values. Raster file does not appear to have any "NO data" values in the domain we are interseted in, however, running zonal stats does not produce appropriate results. We are only generating values for 3 polygons out of 94 selected polygons. Why are we not seeing any values for the rest of the cells? There are definitely values there in the raster file. Zonal statistics only generates data for 3 cells out of 94 selected cells...? The problem is defintely with a raster file and not a shapefile (with polygons) that will have values fields from a raster file as a result fo zonal stats. I am not an experienced GIS user but I was wondering if I am dealing with a certain type of a raster file that I need to do something else with prior to running zonal statistics. Any help or input is really appreciated! Thank you so much
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03-18-2011
11:52 AM
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William, Thank you so much for your post. I did try to work on a much smaller area. I was able to resolve the problem by selecting a very small portion of my shapefile (about 20,000 records) and performing a Zonal Statistics by Table instead using the entire shapefile (with nearly 200,000m polygons). Thank you again Julia
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02-12-2011
06:12 PM
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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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02-06-2011
06:23 AM
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