revised: 05-Feb-2015

NMBGMR Draft Geologic Data Model - v. 1.0.4

In the interests of standardization and interoperability, we are migrating our geologic maps into the USGS NCGMP09 data model. However, our well data model is still actively being used. Documentation for the NMBGMR geology data model is being provided for users with legacy data in this model. We also hope that it will provoke discussion in the ongoing effort to improve NCGMP09 and other models.



Topological rules define the spatial relationships between feature classes and the constraints within particular feature classes. For instance, geologic contacts must bound polygons of a particular lithologic unit. Likewise, contacts cannot have dangles (end in space). These rules are encoded in the geodatabase and ensure consistency and data integrity.

Cluster Tolerance

Two (or more) points or vertices are considered to be coincident in the geodatabase if the distance between them is less than the cluster tolerance. The cluster tolerance chosen should be dependant on the accuracy of the data. For geologic maps, most data is unlikely to be positioned at an accuracy greater than that of a handheld GPS -- 3 meters at best with WAAS. However, differential GPS positioning can be considerably better. For now a cluster tolerance of 0.01 meters will be used. Points positioned by high-precision GPS should either not participate in the topology (and therefore not be affected by the cluster tolerance) or should have a higher rank in the topology.


Each feature class that participates in the topology is relatively ranked based on accuracy. When points or vertices are adjusted because they fall within the cluster tolerance, the point with the lower rank will be moved (1 is the highest rank).

Feature Classes that participate in the topology and their ranks:

Rules (* these rules should be valid before building polygons)




Geologic Units (Lith_poly):

Map Boundary/Extent: