I downloaded the 14 Gigabyte file on the US Cropland Data so I could do some spatial analysis regarding Corn and Soybean crops.
While I am able select different elements within the layer, I am not allowed to make a new layer of just Corn and Soybeans. Why is this shapefile acting like a static image file?
Am I missing something? Does the file need to be converted into something else?
Could you post the download link from where you got the data? This way we can take a look at it to help you answer your question.
Chris Donohue, GISP
Happy to. I got it from here. Like I said, I can select those elements, but it won't seem to let me make a layer out of it.
Is the file you downloaded this one? Just wanted to confirm, as it will take a while to download.
Click to download the national 2014 CDL zipped file National 2014 CDL (1.4 GB)
Chris Donohue, GISP
Yes that's the one.
Hmmm, this file is a bit problematic, as says it will extract out to 5.99 Petrabytes, which requires a bit more space than I have free
Also, it appears to be a raster image. I suspect it is as it has an .rrd file.
I found this explanation on the web:
File type specification:
The ige file extension is related to ERDAS IMAGINE, a geospatial data authoring software, and used for so called Large Raster Spill files.
When creating images requiring more than 4GB of disk space in Imagine a two file dataset is created. The .img contains the traditional superstructure, but the actual image data is kept in a separate non-HFA file format, normally with the extension .ige. This is presumably done to get around the 32bit file offset limitations of HFA format which makes it impossible to address large images.
IGE file extension - Open, view and convert .ige files
So I don't think this is a shapefile as you expected. However, I can't open it to verify this.
Chris Donohue, GISP
The Cropscape FAQ offers this explanation:
Common User Questions
Is the CropScape/Cropland Data Layer available in a shapefile format?
We do not offer the data in a vector format, such as shapefile. The Cropscape/CDL data can be downloaded in a raster-based GeoTIFF file format and used in most common GIS software. In ESRI ArcGIS you would most likely require the 'Spatial Analyst' extension to perform any in-depth GIS applications using the GeoTIFF file. And any common image processing software, such Erdas Imagine, ENVI or PCI, should be able to perform basic image processing/GIS applications using the GeoTIFF file. This type of pixel-based data does not lend itself to being converted to vector since the resulting polygon file would be enormous. Depending on the size of area you are studying it is technically possible to convert Cropscape data to a shapefile, but it would have to be a rather small area such as a single county or smaller.http://www.nass.usda.gov/research/Cropland/sarsfaqs2.htm#Section3_15.0
Chris Donohue, GISP
Okay one last question. The key says that the spatial analyst can allow me to perform in depth GIS applications with a GeoTIFF file. How?
Here is my goal. The cropscape layer is one of three layers on my map. The second layer is a shapefile that lists every k-12 school in the United States. The third layer I created was a circular buffer zone of 1000 feet around each of those schools.
I want to see which buffer zones overlap with Corn and Soybean fields. Can this be done?
This can be done with GIS. A couple of workflows come to mind, but first a question to clarify what you want:
- Is the desired answer that of "which buffers overlap", or instead "how much of each buffer that overlaps"? For example, are you ultimately trying to find how much corn or soybean acres are within 1000 feet of each school, or instead just that Corn and/or Soybeans exist within 1000 ft of a school?
Chris Donohue, GISP
I want to walk away from this project with a list of schools within 1000 feet of a corn/soybean field.