Timeline for Clipping NLCD Land Cover Data in ArcMap
Current License: CC BY-SA 4.0
9 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jan 16, 2020 at 20:39 | comment | added | Hornbydd | 1) yes, 2) no 3) I used a layer obtained from arcgis online. | |
| Jan 16, 2020 at 19:00 | comment | added | Alexander Martinez | I am giving it a try on a different machine now. Three follow-up Q's as I troubleshoot: 1. Did your attribute table have more than a single row (i.e., did it have pixel counts for multiple categories like the parent raster?) 2. Did you perform any projections/transformations of the data when you brought it in? 3. Did you just use a generic states polygon shapefile for clipping? Thanks for your continued insight; this is a very basic task and I am not sure why I can't get the results I anticipate... | |
| Jan 16, 2020 at 18:40 | comment | added | Hornbydd | That's is exactly what I did. Maybe it is a machine related issue? Or graphic card issue? Try the whole process on another machine? | |
| Jan 16, 2020 at 17:36 | comment | added | Alexander Martinez | @Hornbydd, just to clarify the parameters for the clip you executed. Input Raster == NLCD.img; Output Extent == states.shp (I made a single small state a selected feature); Use Input Features For Clipping Geometry == CHECKED; Output Raster Dataset == .tif format, NoData Value == 0, Maintain Clipping Extent == UNCHECKED. In the environment settings I set Snap Raster == NLCD.img file. Once the clip was complete with these settings, I used Build Attribute Table with overwrite == CHECKED. The result this time was a completely empty raster attribute table. Have I misinterpreted your process? | |
| Jan 15, 2020 at 23:42 | comment | added | Hornbydd | I just ran the clip on that dataset then rebuilt the RAT and I get a normal attribute table... My output format was tif, nodata was set to zero, snap raster environment was set to the img file. Then for rebuilding the RAT , I ticked on overwrite. All came out as expected. Make sure you have no selection on the raster. | |
| Jan 15, 2020 at 19:54 | comment | added | Alexander Martinez | Thanks. I re-ran clip to avoid re-sampling, which seems like the right choice since it maintains pixel size of the original raster. However, the output .img file att_table remains the same: a single row, pixel class value = 0, and all the pixel counts have been lumped into this single category. Really odd. I looked at options for Join Field -- will this work given that the clipped raster attribute table has only a single row? That is, rows from the original raster file table with the appropriate pixel values are not present in the clipped table. Any add'l insight is appreciated | |
| Jan 15, 2020 at 0:38 | comment | added | Michael Stimson | Do the output images have a Raster Attribute Table (.dbf) file associated with them? You would think if the original has raster attributes the clipped would also. According to the help the environment resampling method is used by the Clip_management tool, try to avoid resampling by setting Snap Raster to your original, then if the attributes haven't been maintained build the RAT and use Join Field to copy the values from the original to the clipped. | |
| Jan 15, 2020 at 0:02 | comment | added | Alexander Martinez | Thank you for the detailed response. Selecting individual state polygons in the shapefile worked perfectly, and I can use modelbuilder to iterate over the remaining states. One issue persists though: the clip converts the different pixel values in the original raster to a single pixel classification (value = 0). Even after I recalculate statistics and use the Build Raster Attribute Table tool, this remains the case. For some reason, the pixel information is not translating correctly during the clip. Any idea what I am missing? | |
| Jan 14, 2020 at 23:09 | history | answered | Hornbydd | CC BY-SA 4.0 |