The Esri Grid format for storing raster data has been around for…well, longer than this writer has been doing GIS. But we keep learning about things that need to be added to the documentation. I’m sure those original Grid users could probably tell me more than I ever wanted to know about the format, but here’s a limitation that was news to me.
The name of a Grid has certain limitations, but did you also know that there’s a limit to the number of Grids that can be stored in a workspace? The following lists the theoretical maximum number of Grid datasets that can be stored in a single workspace directory:
- less than 5000 floating point Grids, or
- less than 3333 integer Grids, with VATs (less than 5000 if no VATs), or
- less than 10000 Grid stacks
The preceding numbers are the theoretical maximums. If you have a process that will create interim Grids (and therefore files in the INFO directory) these numbers will be less. Additionally, if you are storing a mix of files, such as Grids and coverages, you will store fewer.
These numbers relate to the number of files in the Grid folder that store information in the INFO directory. The limit is 10,000 (well, 9,999), but it’s not the total number of files in an INFO directory, it’s the number of files pointing to the files in the INFO directory. For each Grid, there are two files in the Grid’s folder pointing to files in the INFO folder: the BND (boundary) files, and STA table (statistics) files (9999/2?5000). When a Grid has a VAT, this also points to files in the INFO directory, so the number that can be stored is reduced again (9999/3?3333). A Grid stack only has a single file which points to the INFO directory (9999/1?9999).
You can get a count of the number of files in an INFO directory using Windows Explorer.
- Navigate to the INFO directory.
- Select all the *.dat files (each Grid file points to a .nit and a .dat file).
- Right-click and select Properties.
This will give you the count of files. Regardless of the data is in the directory (Grids, stacks, coverages, etc.), when that number gets to 9999, the INFO directory is full and you’ll get an error message to the effect of: “Fatal Error: (INFDEF) directory full”. If you happen to come across this limit, you can either create a new workspace to work in, or remove any data that is no longer needed.