Checking and repairing geometries


ArcGIS applications are built with the assumption that the feature's geometry follows certain specifications. When the software encounters data which does not follow the specifications, the result can be unexpected software behaviors (including crashes) and incorrect analysis results.

Origins of bad geometry

The Shapefile format is an open format to which many software packages write to natively. Unfortunately some of these software packages (sometimes due to bugs) do not follow the documented specification for the Shapefile format.

Also of note is that when Shapefiles are loaded into personal or file geodatabase, the features are copied as they are (with the geometry problem) to these other formats, so the same caution and care which needs to be used when using Shapefile data needs to be taken when using personal and file geodatabase feature classes.

The exception to this when the data is loaded to an SDE Geodatabase. Before it is stored in the feature class, each record's geometry is checked for geometry problems, and repaired if necessary.

Responsibility

The onus is on the data's user to verify that it contains features with valid geometries before using it. Once check geometry has been run on a dataset, it is not necessary to check it again if the data has not been modified.

Finding and fixing geometry problems

The Check Geometry tool will generate a report all features with geometry problem within the feature classes provided. Then to "fix" the problems use the Repair Geometry tool.

Below is the list of geometry problems:

See Also