The topological editing capabilities of Mapboard GIS are a major step towards iterative geologic mapping. When topological editing is enabled, unit definitions snap to their enclosing linework, allowing the structure of the map to emerge as mappers focus on capturing data.
In Spatialite mode and Image mode, the onboard Spatialite engine is used to manage topological relationships. The reference implementaion of topological editing capabilities is the PostGIS Geologic Map topology solver operating in Tethered mode.
Spatialite support for topology is slower and more bug-prone than the PostGIS reference implementation. The underlying algorithms will be improved over time. Please file issues as needed to document unexpected behavior.
In both modes, the Topology settings panel manages whether topological editing is active, and whether filled map faces are shown. During topological editing, each change to the map results in a rebuild of the modified area. The PostGIS Geologic Map engine is good at finding the minimum set of relationships to change, but the Spatialite backend currently uses a less efficient algorithm.
Onboard topological solving is a complex, battery-draining algorithm, and iPads have limited system resources. Real-time topological solving should be turned off during intensive field use if stable power availability is a concern.