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This page first made public: Jul 27, 2010

Mapping Magnetic Intensity Data Using a Trend Surface Analysis

Ann K. Deakin, SUNY Fredonia


Provides students with an opportunity to work with and interpret magnetic intensity data (nT). Challenges them to explain magnetic intensity to an introductory geology student.


Type and level of course
This lab was assigned midway through the semester in GEO 301, Cartography. Cartography is an upper level elective in the Geosciences Department. It is a required course for the Minor in GIS, so there may be non-geo majors in the course.

Geoscience background assumed in this assignment
Ideally, the assignment assumes an introductory knowledge of geoscience and perhaps a course in geophysics. The assignment is, however, within reach of non-geo majors.

GIS/remote sensing skills/background assumed in this assignment
The assignment assumes at least an introductory course in GIS. Ideally, a 2nd course would have been completed, as well.

Software required for this assignment/activity:
ArcEditor 9.3 with Geostatistical Analyst, Spatial Analyst & 3D Analyst

Time required for students to complete the assignment:
1 week lab assignment


GIS/remote sensing techniques students learn in this assignment
Students use buffering, spatial selection, global polynomial interpolation, vector to raster conversion, raster extraction, and 3D visualization to model a trend surface for magnetic intensity.

Other content/concepts goals for this activity
This assignment actually resulted from a conversation I had with several geo students in the class who didn't have a firm understanding of magnetic intensity, how such data were captured and how it could be used.

Higher order thinking skills goals for this activity
Learning about a concept to the extent that you can explain it to a novice, either in writing or verbally, can aid in a stronger understanding of the concept. The goal was for students to achieve that understanding by working with a publicly available primary data set in the context of a GIS analysis. They then had to conduct some research of their own to determine what magnetic intensity of the local area can tell someone about the underlying structure.

Description of the activity/assignment

Students created a 1-page layout for an introductory geology textbook that explains magnetic intensity (nT). At a minimum, their layouts had to include an ArcScene map of magnetic intensity (nT) for the local area (Chautauqua County, New York), a legend, and a text box explaining magnetic intensity using Chautauqua County as an example. Students used a Trend Surface Analysis (Global Polynomial Interpolation) to represent magnetic intensity as a surface. They were allowed to include other graphics to support their explanations as long as the sources for the graphics were cited.

Given that most of the students enrolled in the course were geo majors, I structured this assignment to address what I thought was a gap in their knowledge. (Ironically, it was the Criminal Justice major/GIS minor who submitted the strongest layout.) I was also seeking to combine several concepts discussed in class thus far, including layout and design and representing continuous surface data.

Determining whether students have met the goals

I evaluated the students' 1 page layouts in terms of their explanation of magnetic intensity - clarity and accessibility - and in terms of adherence to cartographic principles - figure ground contrast, typography, color, balance, proportion, etc.
More information about assessment tools and techniques.

URLs and References

GeoNet Gravity & Magnetic Dataset Repository at PACES (Pan American Center for Earth & Environmental Sciences) at the University of Texas at El Paso. http://research.utep.edu/default.aspx?tabid=37229

I accessed and downloaded the data on 26 February 2010. It was originally a text file that I brought into Excel, edited it for use in ArcMap, and then created an event theme and eventually a shapefile of the data in ArcMap.

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