What is the UIS?

The Union Internationale de Spéléologie (International Union of Speleology) is an international commission created to “encourage and facilitate the systematic collection and responsible use of cave, karst and related data on an international basis.”

For more information, visit the official UIS website.

The Grading System

The UIS Grading system uses a combination of individual grades for the different parts of a map. So, you will find a survey grade, a map detail grade, and then additional qualification grades that further explain how the data was managed.

The image below is a summary created by Survey Down. Please note the grading format shown at the bottom of the table.

Note that the UIS also specifies that ranges of grades should not be shown on a map. The cartographer should give their work a single grade based on the realistic accuracy of their full map.

To view the complete UIS grade system, download the PDF here:

Grading Underwater Survey

It was decided by the UIS that underwater measurements would not be valid under the current rating system due to the challenges presented by underwater survey. However, it was agreed that divers could still write a grade with the prefix of “Equivalent to...”

For example, an underwater cave map with a grade 3 survey, grade 4 map details, and additional qualifications B, C and E, would be written as Equivalent to UISv2 3-4-BCE.