In the 1950s, the basic geologic map-making process was the same, but by then, the materials used to make geologic maps had changed. The only topological question that was asked was “Are any adjacent polygonsof the same color?”
Application of color with a brush meant that the color sometimes went outside these lines. Lines bounding the areas on the maps representing rock outcrops did not necessarily close. For example, mappers colored early geologic maps by hand mostly with watercolors. Long before geographic information systems (GIS), geologic mappers and cartographers were less concerned with questions about topology than they are today. An example of this is the following query from a geologic map: “Show as a polygon the region where every point on the constructed polygon boundary is ten miles from the San Andreas fault system.”
Point to polygon (is a point on the inside, outside, or on the boundary of the polygon?).Polygons that outline a part of an image.In addition to the making of geologic maps, topology enhances analysis of the features on a geologic map in the following general cases: He said, “Topology is the relationships that can exist among the geometries of spatial features…(and) is a major step towards minimizing the number of points, lines, and polygons to digitally capture and manage a geologic map.” Data accuracy and validation are enhanced by the properuse of topological rules. Points that are measurements on a fault or other structure represented by a line must be covered by the line with which they are associated.ĭave Viljoen (Geological Survey of Canada) in 1997 presented a paper about geologic map topology at the first Digital Mapping Techniques workshop.Polygons must not overlap one another, must not have gaps between one another, and map unit polygon edges must be covered by boundaries (contacts and faults).A boundary line must not cross over itself or lie on top of itself.I recommend the following kinds of topology for making geologic maps with ArcGIS: The main point of this paper is that the application of topological structure in ArcGIS is beneficial to converting geologic maps into digital databases that are bothrigorous and efficient. Topology in ArcGIS is expressed in the form of rules that govern the allowable relationships among geometric entities and objects, which if carefully followed, lead to digital database structures that reduce the likelihood of errors and inaccuracies and that facilitate automated analysis.
#Topology rules arcgis 10.6 software
Various tools have been developed to aid in creating geologic map databases that contain the complex information and relationships expressed in geologic maps, but not all tools have been equally successful.ĮSRI’s ArcGIS software represents one of the latest developments in this process, and it differs from earlier tools in that a topological framework is optional. Geologic maps contain abundant data about the locations of different kinds of rock materials, as well as relational information about the contacts between contrasting units and the nature of these contacts (for example, depositional contacts, intrusive contacts, faults, etc.). Topology helps define as well the functional relationships among geologic map objects (feature classes or sub-themes, and themes or feature data sets), the feature geometries of which provide the framework for these representations. Box 25046, MS980, Denver Federal Center, Denver, CO 80225 Telephone: (303) 236-1320 Fax: (303) 236-5349 e-mail: as a term used in the context of a digital representation of spatial data in two dimensions, pertains to the relationships among feature geometry objects such as points, lines and polygons. Geological Survey Open-File Report 2004–1451īy Ronald R. USGS OFR 2004-1451: The Use of Topology on Geologic Mapsĭigital Mapping Techniques '04- Workshop Proceedings
0 kommentar(er)
