Thoughts on editing a geologic map for topology in ArcMap and a GeMS data model.
Channel: Phil Miller
Date: 2021-03-11

This video is about some of the general topics regarding topology in a GIS environment using the GeMS data model.


Make sure before you start mapping that "snapping" is turned on, feel free to also turn on midpoint snapping, and snap to sketch as these are very helpful in preventing most topology errors.


Typical procedures:
1. Turn off visibility or selectability of all the layers except ContactsAndFaults, MapUnitPoints. Make MapExtentPoly visible but not selectable.
2. Zoom to MapExtentPoly or ContactsAndFaults to have the complete map area in the data-view extent.
3. Load the database topology into your project.
4. Start an editing session (if needed, add the topology toolbar, it will then be activated within the editing session).
5. Select the "Validate in Current Extent" to run the topology or "Validate Specified Area."
6. Open the Error Inspector window from the Topology toolbar. 
7. You can show the errors associated with all the rules, however, it is best to work through each rule type one by one systematically starting with "ContactsAndFaults must not have dangles." 95% of the line errors relate to dangles, plus have the advantage of fixing some of the "ContactsAndFaults must not intersect" errors. "must not intersect is not required in GeMS, but is a great tool to use to validate your geology.
8. You likely will have tens to hundreds of dangle rule errors. This is fairly common. Use the method outlined in the video using the "error inspector" to navigate through all of your topology "line" errors.
9. Fix all the line errors first.
10. Save periodically!!! Save edits, and save the mxd. This will save you heartache. 
11. After you fix all of the line errors or as appropriate mark them as exceptions, you can make polygons from ContactsAndFaults and your MapUnitPoints
12. If your polygons appear to have been created correctly, copy your temp polygons into MapUnitPoly

13. Validate topology again (zoom to MapExtentPoly, deselect any features that you may have selected, then validate topology in the current extent) and fix any topology errors or mark as exceptions with regard to the MapUnitPolygons polygons. Check all polygons that contain no points or contain more than 1 point to make sure the poly is attributed correctly. Delete any extra MapUnitPoints if multiple points are present within a single polygon's area.