Working with Tabulate Area
If you encounter a problem with Tabulate Area, there are certain issues that typically are the root cause. Some of these issues are listed in the following sections, as well as some suggestions on how to work around them.
"One or more inputs have no associated attribute table" error
This error is often the result of the zone input not having the required attribute table.
- If the zone input is a raster, first use Build Raster Attribute Table to create an attribute table for it.
- If the zone input is a feature dataset, in the internal conversion to raster the attribute table will be automatically created.
"Unable to allocate memory" error
The program uses internal tables to perform the area calculations. If the values of the zone input have a very large range (millions), the memory requirements to process these tables can approach or exceed the specified system paging file size.
If the amount of memory configured is insufficient, the operation will fail with the "Unable to allocate memory" message. There are two general solutions to this problem:
- You can increase the virtual memory setting to avoid this error. However, the operating system will not immediately release the virtual memory it needed when the tool completes. This can cause a general slowdown in the performance of your machine.
- An alternative, and preferred, method is to reduce the range of the zone values. Add a new item to the zone attribute table with an index value, use Tabulate Area on that item, then relate the results back to your original zone input.
For example, if there are only three zones of values—2,120,000; 4,070,000;, and 9,540,000—dividing the values by 10,000 will give zone values of 212, 407, and 954.
Output areas are smaller than expected
Some of the area values in the output table may be smaller than what you may have expected.
This is typically related to NoData cells in the input with a higher resolution becoming a larger area of NoData after it is resampled to match the other, coarser input.
To avoid this situation, use either Resample on the coarser input raster to make it match the resolution of the finer input raster, or set the Cell size raster analysis environment to Minimum of Inputs.