Error occur during generating CNgrid in HECgeoHMS.

Question

i m bhavna pardhi ME Water resources engg. student doing project at arc gis 9.3. the error occur during  generating CN grid in 
HECgeoHMS.

system.NullReferenceException object reference not set to an instance of an object.
   at
ESRI.APWR.HECgeoHMS9.GPGenerateCNGrid.GenerateCNGridWK (Aplayers,aplayers,Int 32 debug, ITrackcancle & Trackcancle, IGPmessages &messages,string &exMessage)
please send me solution of this problem.
 
bhavnapardhi90@gmail.com

V_StuartFoote · Answer

Copying this from the Geoprocessing forum as it has more complete details of Bhavna's installation...hi, I am bhavna using ArcMap9.3 with Windows 7 home basic 64 bit. I installed HEC-GeoHMS 5.0, ArcHydro tool9 for watershed modelling. when i tried to generate CNGrid (input fil, Lulc_soil_union and CNLookup table) from utilities of HEC-GeoHMS, its doesnot generating CNGrid (Grid formate) and showing the massage below
" System.NullReferenceException: Object reference not set to an instance of an object.
at ESRI.APWR.HECGeoHMS9.GPGenerateCNGrid.GenerateCNGridWk(ApLayers apLayers, Int32 debug, ITrackCancel& trackcancel, IGPMessages& messages, String& exMessage)
Failed to execute (GenerateCNGrid)."

bhavnapardhi90@gmail.com

V_StuartFoote · Answer

Looks like you are not the only one to have had problems with the GPGenerateCNGrid procedure in those versions of GeoHMS, found this in the Geoprocessing forum unfortunately no feedback there either.  Default CNGrid not generating

hi, I am uisnin ArcMap9.3 with Windows 7 32 bit. I installed HEC-GeoHMS, ArcHydro for watershed modelling. when i tried to generate CNGrid (input fil, Lulc_soil_union and CNLookup table) from utilities of HEC-GeoHMS, its doesnot generating CNGrid (Grid formate) and showing the massage below
    " System.NullReferenceException: Object reference not set to an instance of an object.
    at ESRI.APWR.HECGeoHMS9.GPGenerateCNGrid.GenerateCNGridWk(ApLayers apLayers, Int32 debug, ITrackCancel& trackcancel, IGPMessages& messages, String& exMessage)
    Failed to execute (GenerateCNGrid)."

Pls anybody explain me

Often specific problems are not with installation or configuration of the H&H programs (ArcHydro, GeoHMS, GeoRAS) but with missing steps or misconfigured input data. True in these older releases, and still true. 
Here are links to HEC maintained user manuals for GeoHMS versions 4.2 and 5.0--look in Chapter 12 - Utilities of either for discussion of the Generate Curve Number Grid utility.  Understanding the necessary input components should help.

HEC link to HEC-GeoHMS_Users_Manual_4.2 (pdf)
HEC link to HEC-GeoHMS_Users_Manual_5.0 (pdf)

If you find you are providing all preprocessing and required input grids and are still having this issue, please post back and we'll try to help.

Stuart

V_StuartFoote · Answer

bhavna,

You'll need to provide more detail about your ArcGIS 9.x installation, and version details for GeoHMS and ArcHydro you have installed for anyone to be of help.

Regards,

Stuart

p.s. have moved this post to the Hydro forum where more assistance for the HEC GeoHMS and GeoRAS tools is available, so you'll have some chance of receiving an answer.