Incorporate GPS into Geologic Mapping

William Montgomery, New Jersey City University


This activity is an easy and fun way to incorporate GPS into a Field Methods course. It facilitates "asynchronous" learning by enabling urban, non-traditional students with complex schedules to visit field locations


Type and level of course
This activity introduces students to the use of GPS in locating outcrops or other features in the field. As such, it has applicability in almost any course that requires mapping and/or feature location. GPS-based feature location can be used in lieu of, or an adjunct to, classical mapping methods such as pace-and-compass and/or plane table / alidade.

Geoscience background assumed in this assignment
The student should be able to use a Brunton compass to measure strike and dip of bedding or other planar features if GPS is being used to locate outcrops as part of a geologic mapping exercise.

GIS/remote sensing skills/background assumed in this assignment
The student should be able to visualize how X.Y coordinates (e.g., Longitude and Latitude or State Plane or UTM coordinates serve to locate features on a map.

Software required for this assignment/activity:
GPS receiver that displays Lat-Lon or other coordinates

Time required for students to complete the assignment:
Travel-time to/from field location plus lab time to make geologic map.


GIS/remote sensing techniques students learn in this assignment
The main GPS goal of the activity is for the student to be able to use GPS-based coordinates to find outcrops that have been previously located by the instructor.

Other content/concepts goals for this activity
The student should be able to measure strike and dip of bedding at approximately half a dozen outcrops and use this information to make a geologic map and cross-section that portrays ground surface and pertinent geological surfaces (e.g., Formation or lithologic contacts).

Higher order thinking skills goals for this activity
The student should be able to employ 3-dimensional visualization and proper horizontal and vertical scaling to create an accurate geologic map and a properly-scaled cross section.

Description of the activity/assignment

This activity includes an on-campus, pre-activity in which students use Brunton compasses to measure strikes and dips of boards set into the ground to simulate a plunging antiform (or synform). The students are given a scaled, color orthophoto of the campus map area and are instructed to use pace and compass methods (learned earlier in the course) to properly locate the 4 boards on the orthophoto; this gives students practice locating "outcrops". NOTE: This pre-activity could be modified easily to incorporate GPS positioning of the "outcrop" boards, which would give students pre-activity experience with GPS as well as practice with the Brunton.

The actual field activity (and the maps included with it on this website) centers around High Point State Park in northwestern New Jersey. Students map locations and structural attitudes of one or two outcrops of Ordovician Martinsburg Fm. sandstone and shale (locally slate) and a number of outcrops of unconformably-overlying Silurian Shawangunk Fm. Sandstone (locally quartzite). The two formations are sufficiently different in appearance that even introductory students find identification relatively straightforward. The contact between the two formations is not exposed in the field area, but outcrops are sufficiently close together and of sufficiently different attitude to postulate that the contact is unconformable.

The recent introduction of GPS into this exercise has provided an opportunity for: 1) "asynchronous learning" for our nontraditional, diverse students with their complex schedules, and 2) fun for the students, in that: 1) the professor does not need to take multiple trips to the State Park to point out the outcrops to students who missed the first trip, and 2) there is an element of "orienteering" or "geo-locating" involved for our primarily urban-dwelling students in finding the outcrops.

The incorporation of GPS has enabled students who have missed the original field trip to still be able to participate in the activity, and to achieve the critically important learning goals of building a geologic map and building an accurate, true-to-scale, geologic cross section.

Determining whether students have met the goals

Successful students, or teams of students, correctly:
  • Locate rock outcrops
  • Measure strike and dip of bedding
  • Map the geology of the small field area
  • Build an accurate, true-to-scale cross section that accurately depicts ground surface, infers a formation contact, and shows correct structural attitudes.
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