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About SDB_Engr

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    Pittsburgh, PA
  1. On July 18th I posted a request for information related to computation of composite Curve Numbers with WMS using NLCD images. I received a response that WMS version 9.0 offers the ability to download 2006 NLCD data using the Get Data tools and it reads the data as a land use grid. I just tried that feature on a modeling project that I recently completed. I had previously used GIRAS based LULC shapefile data on that project with disappointing Curve Number results. I had to modify the curve number using aerial photography of the relatively small watershed in conjunction with SSURGO polygons displayed in WMS, and a spreadsheet that computes composite CN's based on percentages. I felt there had to be a better way, and I learned that this task could be done with NLCD data. That prompted me to post my question on July 18th. I was pleased to see that the 2006 NLCD download with the Get Data From Map tool worked flawlessly and I proceeded to generate a CN from WMS very quickly. However, once again the CN computed by WMS was not appropriate based on the land use and land cover characteristics of the watershed. The polygon based CN was too high, and the 2006 NLCD raster based CN was way too low. I believe the problem is that land use/land cover data resolution of the 2006 NLCD data is poor in the project area, which is located in southwestern Pennsylvania. I have learned that there is a different raster dataset circa 2005, developed by Penn State University for the entire state of PA, and funded by the state's Department of Conservation and Natural Resources (DCNR). This data would offer an alternative to 2006 NLCD in situations like this. The raster is in the form of a large TIFF file. Based on a little research, I believe this kind of land use/land cover TIFF can be converted into a land use grid, but I do not know how to do this. I have been doing hydrology and hydraulics modeling for a long time, but I am a new user of GIS technology, with WMS being the only GIS software that I am somewhat acquainted with. Is there a way that I can convert this large TIFF into a land use grid in WMS, or is a different piece of software required to accomplish the task?
  2. Thank you for providing this information Chris. I will give it a try.
  3. I am looking for information/tutorial on generating composite Curve Numbers with WMS using NLCD TIFF images with worldfile to generate land use/land cover data. I have seen some information that indicates WMS can utilize the NLCD Landsat based data, but have not been able to find detailed steps for how to do this. GIRAS based LULC shapefile data is dated, and was not very accurate for a project I just worked on.
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