KB10741 - Sometimes, upon closer zoom levels, a smaller polygon shape located inside another polygon disappears. Why?

Probably your polygon layer is topologically incorrect. Polygons in the same layer should never overlap. SQL database layers and R-Tree enabled file layers use spatial indexes which means that the order that shapes are rendered can vary dependent on scale. In your case, at some zoom levels the overlapping area of the larger polygon is being drawn after the smaller polygon located inside that polygon is drawn. The result is that the smaller polygon is hidden.

A typical example of this type of problem is a layer with larger polygons representing property parcels with smaller polygons inside representing buildings. In such situation, the proper solution is to use a separate layer for different type of feature.

We suggest performing a topological cleanup of your layer using the topology builder/corrector feature of the TatukGIS Editor product.