Flathead County, Montana

The example shown above is an illustration of township T29NR20W in Flathead County, Montana.  The map was created using GCDB information obtained from the Bureau of Land Management.   The GCDB was built from GLO records and control from digitized USGS positions.  Flathead County staff research the county record and change the GLO bearings and distances with retracement data. They also "tighten up" the control with GPS.  Corner recordations are researched to ensure there is a continuous chain from the GLO record to the present. Then resource grade GPS is used to obtain geographic coordinates, which are used to readjust the GCDB.

In this way, BLM data provides the initial basis for the map, and, where applicable, updated county survey data is used as a basis for developing the current map.   Flathead County staff regard this as a dynamic process.  They use the BLM routines to break the sections down.  Then information is applied from county surveys and GPS.

Sometimes significant readjustments are necessary.  For example, the lower right side (sections 22, 23, 24, 25, 26, 27, 34, 35, 36) were readjusted after finding a 160' surveying error.   The adjustment "blew up" in that area. That is, the adjustment tolerances indicated that further research and control was necessary to determine exactly what the problem was.   Sometimes the error is the mis-report of a distance or bearing and sometimes it is a measurement error. In this instance, it was a measurement error. Flathead County staff went out to the field, located the monuments on the ground, and collected a GPS position for the monuments north, south, east, and west of the problem.   They then then "loosened" the original distance and bearing weight and allowed the least squares to show just how big the problem was.

This problem area is illustrated as the circled area in the image below.  Notes made by Flathead County staff indicate the readjustment.

Crosswalk Of Flathead County Example To The Cadastral Data Content Standard

The table below illustrates some of the data elements used in Flathead County which have corresponding entities in the Cadastral Data Content Standard.

Back To Montana Cadastral Mapping Project

Links to the Course Modules: [Quick Reference] [Introduction] [Module 1: Purpose and Benefits of the Cadastral Data Content Standard] [Module 2: How the Standard Was Developed] [Module 3: Other Standards and Related Activities] [Module 4: Data Modeling Techniques, Rules and Diagram Conventions] [Module 5: Crosswalks, Translations, and Examples] [Module 6: Understanding Compliance with the Standard] [Module 7: Maintenance of the Standard] [Module 8: User and Technical Support] [County Recorder Module] [GIS Specialist Module] [Surveyor Module] [Glossary]