In this tutorial you will learn what valid means for a geometry and how to check validity in QGIS 3. You will also see how to fix validity problems and how to make a geometry simple.

## Geometry validity

Points and lines are always valid. A POLYGON is valid if the polygon boundary rings are simple (do not cross or self-touch). Because of this a polygon cannot have cut lines, spikes or loops. This implies that polygon holes must be represented as interior rings, rather than by the exterior ring self-touching (a so-called “inverted hole”).

## Geometry simplicity

Geometry has no anomalous geometric points, such as self-intersection or self-tangency.

## 🔴 What is QGIS?

QGIS is a professional GIS application that is built on top of and proud to be itself Free and Open Source Software (FOSS).

## 🗺️ Tales from the GIS?

Tales from the GIS is a geospatial journey into the fascinating world of Geographic Information Systems, telling you stories about nature and world.