Spatial Analysis of Raster Data - An Antarctic Example

Mark Helper, University of Texas at Austin, Department of Geological Sciences

Summary

Using Antarctic elevation and ice thickness raster data sets, this exercise uses tools available in the ArcGIS Spatial Analyst and 3D Analyst extensions to answer questions and produce maps that display Antarctic topography, sub-ice topography, the effect of higher sea level and the effects of isostatic adjustment from ice removal.

Context

Type and level of course
Designed for an upper division undergraduate elective/introductory graduate course in GIS&GPS Applications in Earth Sciences.

Geoscience background assumed in this assignment
No geoscience background is assumed. The concept of isostasy is introduced at a very basic level.

GIS/remote sensing skills/background assumed in this assignment
Familiarity with:

1. Basic ArcMap tools and functions - standard toolbar, Layer Properties, Table of Contents, Layout and Data views, labeling; layer files.
2. Vector and raster data formats and differences;
3. Concept of projected coordinate systems

Software required for this assignment/activity:
This exercise was originally written for ArcGIS 9.0 ArcInfo with Spatial Analyst and 3D Analyst extensions. It is entirely compatible with ArcGIS 9.3 ArcInfo with Spatial Analyst and 3D Analyst. 3D Analyst is used to calculate ice area/volume (a minor component of the exercise) but is otherwise not required.

Time required for students to complete the assignment:
3 hours

Goals

GIS/remote sensing techniques students learn in this assignment
GIS techniques introduced and practiced in this exercise are:

1. Creating a custom projection by modifying an existing one;
2. Use of an available layer file to symbolize vector data;
3. How to use stretched and classified symbology for raster data;
4. Use of an Analysis Mask;
5. Clipping raster data to an Analysis Mask;
6. Producing a Hillshade;
7. Query of raster data;
8. Creating binary rasters with the Raster Calculator;
9. Use of a conditional statement in the Raster Calculator;
10. Addition and multiplication with the Raster Calculator;
11. Creating contour lines from a raster;
12. Using the Area and Volume Statistics in the 3D Analyst extension.
13. How to examine and use raster data set properties - resolution, bit depth, file size, file format;

Other content/concepts goals for this activity

1. Discovery and exploration of a continent whose geography is virtually unknown to most students:
2. The effects of global sea level rise on the distribution of land masses and the physiography of an ice-free Antarctica;
3. The magnitude of isostatic rebound upon removal of a continental ice sheet;
4. The combined effects of isostatic and sea level rises on the physiography in Antarctica.

Higher order thinking skills goals for this activity
Comparison of published and derived ice volumes requires critical evaluation of the data sets.

Description of the activity/assignment

In this activity, students use 1:5,000,000 scale continent-wide Antarctic data sets of surface elevation, ice thickness, bedrock topography, rock outcroppings, and coast lines to examine the effects of ice removal and sea level rise on the physiography of the continent. Datasets come from the Scientific Committee on Antarctic Research (SCAR) and the BEDMAP project.

The emphasis of the exercise is on the nuts and bolts of some of the tools in the ArcGIS Spatial Analyst extension for analysis and display of raster data, with considerably less emphasis on higher order thinking skills. Quoting from the introduction "What does Antarctica look like beneath the ice? A continent of mountain ranges, deep valleys, plains, inland seas, offshore islands and the like exists there, for the most part invisible but for a few features that protrude above the ice. Wouldn't it be nice to have a topographic map in shaded relief of Antarctica without the ice and with oceans filling areas that are below sea level? Wouldn't it be even nicer to have such a map that accounted for the isostatic rise of the land surface that would occur after the weight of the ice was removed? What would the continent look like if sea level rose by an amount equal to the volume of the water locked up as ice? How much ice is there? Digital data are available to make such maps and answers these questions, as is software to do so. Let's have a crack at it!"

The exercise was originally written for ArcGIS 9.0 ArcInfo with Spatial Analyst and 3D Analyst extensions. It is entirely compatible with ArcGIS 9.3 ArcInfo with Spatial Analyst and 3D Analyst extensions. 3D Analyst is used to calculate ice area/volume (a minor component of the exercise) but is otherwise not required

Determining whether students have met the goals

Students are evaluated on the basis of answers to 12 questions throughout the exercise and a finished map showing a derived digital elevation model of Antarctica after isostatic rebound from ice removal and a sea level rise of 80.5 meters.
More information about assessment tools and techniques.

URLs and References

A URL for downloading the data sets for this exercise is provided in the coversheet (see "Other Materials") and within the exercise. The URL contains a zipped file "Antarctic_data.zip" that contains all data need to complete the exercise, as well as a Powerpoint presentation that contains example maps.

Supporting references are contained within the zipped data file for this exercise. The zipped data file for this exercise is "Antarctic_data.zip".

Download teaching materials and tips

• Activity Description/Assignment: Spatial Analysis of Raster data - An Antarctic Example for ArcGIS v. 10 (Acrobat (PDF) 791kB Aug26 14)
• Instructors Notes:A URL for downloading the data sets for this exercise is provided in the coversheet (see "Other Materials") and within the exercise. As noted in the exercise, the data presently available at the SCAR and BEDMAP websites, though superficially similar, are not the same as those needed for the exercise - they have been updated and data at 1:5,000,000 scale are no longer publically available . The exercise could be updated for these newer data, but file sizes are considerably larger and the finer details do little to enhance results.
• Data Set: Antarctic data set (Zip Archive 25.7MB Aug25 14)

Other Materials

• Cover sheet updated for 2014 (Acrobat (PDF) 292kB Aug26 14)