loosen

Sudden errors using NDVI raster data to intersect with overlapping polygons in GME

Discussion created by loosen on Mar 16, 2017

I am experiencing errors with Geospatial Modeling Environment (GME) that suddenly developed after things were working perfectly.


1. Description of software installed:

  • ArcGIS 10.3.1 for Desktop and ArcGIS Service Pack: 0 (build 0); R version 3.3.2; Geospatial Modelling Environment (Version 0.7.4.0)

2.  What I'm trying to do

  • I am using the tool "isectpolyrst." My polygon file has 5718 rows with overlapping buffers. Buffer size is 90m around points. I am trying to extract Normalized Difference Vegetation Index raster data (NDVI; from MODIS) to each polygon. NDVI values range from -2000 to 9000.
  • I do not get an error message. However, the values of the raster I am trying to extract do not match the output. See #3 below.
  • The tool processes very, very quickly. The output value for each polygon is identical (mean = -1.797693e+308).
  • These values are not correct (ie there is variation and the values do not match)
  • The tricky part is the tool worked properly until a few weeks ago. I did not upgrade GIS, nor did I change the files at all.

3. What I've tried to trouble shoot:

  • Double check projections are the same for polygon and raster data.
  • Downloading NDVI files again. Perhaps they got corrupted?
  • Scaling my data to 0-100 values (subtract by minimum value, divide by range, multiply by 100).
  • Converting to different raster file type (TIFF, IMAGINE, GRID)
  • Assigning attribute table to NDVI raster data (no luck)
  • Try on different machines (all have Windows)
  • Using the Zonal Stats as Table II in ArcMap. This is a finicky tool and I can never get it to work on >300 rows

 

I AM STUMPED!!! Does anyone have any ideas on how to proceed? This is an issue I've heard from other folks, but no one found a work around in GME.

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