spatial analysis of raster data: analyzing the effects of ice removal and sea level rise on the...
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Spatial Analysis of Raster Data: Analyzing the Effects of Ice Removal and Sea Level Rise on the Physiography of
Antarctica
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 1
Mark HelperJackson School of GeosciencesThe University of Texas at Austin
GIS/GPS Applications in Earth SciencesCourse and Students:
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 2
Only GIS class in the Department Senior elective, cross listed as Grad.
Course 20 students, TA 3 hrs. lecture, 2 hrs. lab per week Prerequisite - intro. field geology with 3 hr
expose to GIS base map prep., GPS data collection
Context:
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 3
First Lab with Raster Data Sets Previous Labs/Lectures
Data Models – raster, vector Projections Digitizing, Georeferencing ArcMap/Catalog basic
Preparation for Course Project
Raster Techniques/Tools:
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 4
Masking Classifying and Symbolizing Hillshade and Contour Raster Calculations
Analysis Skills:
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 5
Raster Query Strategies Highest/Lowest Elevations Elevation at a point
Raster Statistics Comparing Rasters
Raster Overlay Land vs. Water
Area and Volume Calculations Ice Sheet Properties
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 6
Focus Questions:
Q1: What is the mean, maximum and minimum elevation of Antarctica?
Q2: What does Antarctica presently look like beneath the ice?
Q3: How much ice is there? Q4: What would a “Greenhouse”
Antarctica look like?
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 7
Tools and Data
Tools – ArcGIS 9.x Spatial Analyst (required) 3-D Analyst (optional; area and volume
calculation)
Data – SCAR and BEDMAP sources Posted for download as ~27 Mb Zip file
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 8
Vector Data - Coverages
Point South Pole
Arcs Continent outline Contours
Polygons Land Ice Shelves/Tongues
4.4 km
:-2.6 km
Bedrock ElevationBedrock Elevation(masked)(masked)
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 9
Raster Data (5x5 km ESRI Grids)
4.5 km 0 m
Ice ThicknessIce Thickness
Surface ElevationSurface Elevation
4.4 km M.S.L.
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 10
Strategy:Explore, Map, Visualize, Analyze
Explore – Raster Properties, Metadata
Map/Visualize – Overlay and Symbolize
Analyze - Query and Model
Questions basic to each step are inserted along the way
Explore the Data
Resolution Data type File size Spatial Reference Raster Stats.
e.g. Q1: What are mean, max. min. elevations?
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 11
Explore the Data:Classify Elevations
Equal interval, 200m
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 12
Analysis Skills:Simple Raster Calculations
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 13
Conditional Statements and Binary Rasters
Above or Below MSLBedrock Elevation
Con([bed_elev] <= 0,1)
Map/Visualize:Q2: What does Antarctica look beneath the ice?
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 14
Overlay binary raster with other layers and create a shoreline contour
Above or Below MSL
Bedrock Elevation
=
Final Analysis:Q4: What would “Greenhouse” Antarctica look like?
M. Helper, UT AustinOn the Cutting Edge GIS Workshop 15
1. Calculate new bedrock elevation raster that accounts for isostatic rise from ice removal;
2. Subtract from this new raster elevations equivalent to a higher sea level (~80 m);
3. Overlay a new binary land/sea raster
Elevation change = (Density of ice / Density of Mantle) x (ice thickness)