topic Re: fragstats! help please! in Data Management Questions

fragstats! help please!

adiroth — Tue, 19 Jun 2012 16:49:54 GMT

hi everyone!

i need your help with fragstats!
i keep getting this messege and can't get a reuslts at all ...
the messege :

Unexpected error encountered: [Grid IO error encountered while loading: D:\adi\raster\rasterwc2]. Model execution halted.

what is this?
can anyone help?
i think the problem is in the way i'm saving my raster..

thank you!

Re: fragstats! help please!

AshleyUnger — Wed, 20 Jun 2012 13:24:24 GMT

Check the format of your raster file in ArcGIS. You might not have it saved as a Grid. You can fix this (in ArcGIS 10) using the "Raster to Other Formats" tool.

Re: fragstats! help please!

TheresaBurcsu — Tue, 26 Jun 2012 17:01:46 GMT

Did this work around work for you? I am experiencing the same error.

Thanks!

Re: fragstats! help please!

JeffreyEvans — Tue, 26 Jun 2012 20:52:58 GMT

The updated version of Fragstats, that works with ArcGIS 10, is a bit temperamental. I would recommend converting your raster data to an ERDAS Imagine (img) format. The raster(s) also need to be a single band "signed" 8, 16, or 32 integer. Another recommendation is, that because historically zero values have been converted to 1 on the fly, it is best to avoid zero values in your raster. It is good practice for your projection to also be in meters, which is assumed in Fragstats.

You can convert your raster and specify output type in ArcCatalog by right-clicking the raster and selecting Export > Raster to Different Format in the context menu. In the resulting dialogue, name your output raster with an "img" extension and select "8_BIT_SIGNED", "16_BIT_SIGNED" or "32_BIT_SIGNED", depending on the range of values in your raster, in the pixel type dropdown menu.

8_BIT_SIGNED�??A signed 8-bit data type. The values supported can be from -128 to 127.
16_BIT_SIGNED�??A 16-bit signed data type. The values can range from -32,768 to 32,767.
32_BIT_SIGNED�??A 32-bit signed data type. The values can range from -2,147,483,648 to 2,147,483,647.

Re: fragstats! help please!

SueClark — Wed, 11 Jul 2012 06:37:02 GMT

I figured out the solution to this problem for our case. It might be helpful for others.

We were extracting files using a Python script and arcpy. The grids were extracted using an extract by mask command. In ArcGIS 10 using arcpy and Python, the extract by mask command should look like

outExtractByMask = ExtractByMask(gridLayer, maskLayer)
outExtractByMask.save(outRast)

If you were to run the extract by mask in ArcGIS 10.0 via ArcMap or through the model builder the command would look like

arcpy.gp.ExtractByMask_sa(gridLayer, maskLayer, outRast)

The second extract command will create grids that work with fragstat. The first set of commands will create grids that produce an error. I replaced my commands and the grids now load without error into fragstats.

Re: fragstats! help please!

AntoniosPavlou — Mon, 30 Jul 2012 15:21:36 GMT

hello, and thanks for the tips.
May I ask something as well as I am new to Fragstats? I want to calculate Shannon's entropy to measure the urban sprawl. However,I am not sure whether I should import the classified image that contains all of my classes or if I should just use a binary image of urban and non-urban area. Also what happens if a portion of the image was primarily clipped out based on a shapefile so that the image is not a perfect square? basically I think this part should be set as background (via tools> class properties) instead of being enabled ; do I have to include this class? I am asking because I have try this in both ways and has a significant impact on the SHDI.
Also, I've read that Shannon's entropy ranges between 0-1; some other articles refer to values above one. What is the range of it?