Department of Geography and Urban Studies, Temple University GUS 0265/0465 Applications in GIS/Geographic Data Analysis Lecture 7: Case Study: Interpolation of Glacier Elevation and Analysis of Glacier Area and Volume Change

Purpose To create a spatio-temporal glacier database to support glacier change analysis To integrate various historic and contemporary data sources on glaciers Issues –Representation of 2-D and 3-D glacier geometry –Representation of glaciers at different times –Support for multi-path data retrieval (by glacier, location, time) –Integration of data with varying scales and data quality

Pilot Study: Mount Rainier, Washington Mount Rainier National Park

Spatial Data Layers Glacier ExtentDebris ExtentOriginal Contour

Spatial Data Layers Appended ContourElevation PointsGlacier Surface

Spatial Data Layers Glacier Slope Glacier Aspect Glacier Hillshade

Spatial Data Layers Terminus Position Terminus Position (detail)

Interpolation: Trend vs. IDW

Interpolation: Kriging vs. Spline

Interpolation: Spline Weighting

Managing the Temporal Component of the Spatial Data The ‘Snapshot’ Approach Time t1t1 tntn

Managing the Temporal Component of the Attribute Data The ‘time-normalization’ approach to representing time in the relational data model (Navathe and Ahmed, 1993) Define three types of attribute data: –Feature-based data –Glacier-based, time-dependent data –Glacier-Based, time-independent data

Feature Based Data ablation accum ZONEM_ELEVMETAKEYLENGTH Carbon Glacier, 1913 Carbon Glacier, 1913 Polygon Attribute Table Data that describe the properties of a single feature (i.e. individual polygon) of a glacier at a given time of record

Glacier Based, Time Dependent Data Data that describe the properties of an entire, individual glacier that vary over time ELAAARWGMSMETAKEY Nisqually Carbon NAME Carbon Carbon Glacier, 1913 Morphology Table 1913 YEAR 1971

Glacier Based, Time Independent Data Data that describe the properties of an entire, individual glacier that remain invariant over time Carbon Glacier, all times WACascadeMt. Rainier WACascadeMt. Rainier STATERANGEWGMSMOUNT WACascadeMt. Rainier Tahoma Carbon NAME Cowlitz Location Table

Relational Schema ablation accum ZONEM_ELEVMETAKEYLENGTH Carbon Glacier, 1913 Polygon Attribute Table ELAAARWGMSMETAKEY Nisqually Carbon NAME Carbon Morphology Table 1913 YEAR 1971 WACascadeMt. Rainier WACascadeMt. Rainier STATERANGEWGMSMOUNT WACascadeMt. Rainier Tahoma Carbon NAME Cowlitz Location Table

Glacier Area Change 1913 – 1971

Calculating Glacier Volume Glacier Surface Layer Basal Topography Layer -- = Glacier Isopach Layer

Calculating Glacier Volume Carbon Glacier, 1971 Glacier Isopach Data Layer

Calculating Glacier Volume COUNT THICKNESS K Grid Attribute Table for a Glacier Isopach Layer ∑ T j ∙ A j ∙ C j K j = 1 V = Where: V is the glacier volume; K is the total number of records in the grid attribute table; T is the THICKNESS value of record j; A is the area of a grid cell (400 m 2) ; C is the COUNT value of record j.

Glacier Area and Volume Change,

Data Quality: A Comparison Our 1971 Area and Volume Calculation Results Versus Driedger and Kennard (1986)

Data Quality: Area Measurements Surveying Errors Digitizing Consistency Errors Registration Errors

Data Quality: Volume Measurements

Data Quality: Metadata Buyer Beware! Maintain metadata table (Glacier Based, Time Dependent) –Map Quality –Survey Date –Person Digitizing –Date of Data Digitization