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Mapping landscapes

7110.2 - Cross-Scale Analysis of Sub-Pixel Variations in Digital Elevation Models

Friday, July 7
8:50 AM - 9:10 AM
Location: Coolidge

Terrain is modeled on a grid of pixels, assuming that elevation values are constant within any single pixel of a Digital Elevation Model (DEM) (a ‘rigid pixel’ paradigm). This paradigm can generate imprecise measurements, because it does not account for the slope and curvature of the terrain within each pixel, leading to precious information being lost. In order to improve the precision of interpolated points, this paper relaxes the rigid pixel assumption, allowing possible sub-pixel variations (a ‘surface-adjusted’ paradigm) to be used to interpolate elevation of arbitrary points given a regular grid. Tests based on interpolating elevation values for 5,000 georeferenced random points from a DEM are presented, using the rigid pixel paradigm and different interpolation methods (e.g., weighted average, linear, Bi-linear, Bi-quadratic, Bi-cubic, and best fitting polynomials) within different contiguity configurations (i.e., incorporating first and second order neighbors). The paper examines the sensitivity of surface adjustment to a progression of spatial resolutions (10, 30, 100, and 1000m DEMs), evaluating sub-pixel variations that can be directly measured from 3m resolution lidar data.

Mehran Ghandehari

PhD Student
Geography Department, University of Colorado-Boulder

Mehran is a PhD student and graduate assistant in the geography department, the University of Colorado at Boulder. His research focus is on surface-adjusted analysis in spatial modeling. Mehran's background is in Civil Surveying (Geomatics); Mehran’s research interests include geospatial analysis and modeling, (applied) computational geometry for GIS, analytical cartography, scale and resolution, and terrain modeling.


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Barbara P. Buttenfield

Geography Department, University of Colorado-Boulder

Barbara P. Buttenfield is Professor of Geography at the University of Colorado in Boulder. She is Director of the Meridian Lab, a small research facility focusing on visualization and modeling of geographic information and technology. She is a Research Faculty Affiliate with U.S.Geological Survey Center for Excellence in Geospatial Sciences (USGS-CEGIS); a Faculty Affiliate for the Rocky Mountain Census Research Data Center; and she leads the Data Harmonization project for the CU Grand Challenge “Earth Lab” initiative. She publishes research on cartographic generalization, multi-scale geospatial database design, terrain analysis, spatial data integration, and managing uncertainty in environmental models. She is a Past President of the Cartography and Geographic Information Society (CaGIS), a Fellow of the American Congress on Surveying and Mapping (ACSM) and a Fellow of the University Consortium for Geographic Information Science (UCGIS). In 2001, she was named National GIS Educator of the Year by UCGIS, in the inaugural year of the award.


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Carson J. Q Farmer

Assistant Professor of Geography
Geography Department, University of Colorado Boulder

Dr. Farmer is an assistant professor of GIScience at the University of Colorado Boulder. His research tends to fall under the banner of computational GIScience and encompasses work on networks, transportation, big data, snow/water processes, and geospatial algorithms. Carson is a strong advocate for open source software and open data, and he develops software and tools for spatial-temporal analysis and data-intensive modeling of dynamic geographical processes.


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Nina S.N Lam

Louisiana State University

Nina Lam is Professor and E.L. Abraham Distinguished Professor in the Department of Environmental Sciences at Louisiana State University. She was Chair of the Department (2007-2010), Program Director of U.S. National Science Foundation Geography and Spatial Sciences Program (1999-2001), and President of University Consortium on Geographic Information Science (UCGIS, 2004). Professor Lam’s research interests are in GIS, remote sensing, spatial analysis, environmental health, and community resilience. She has published on topics including spatial interpolation, fractals, cancer mortality, scale and uncertainties, AIDS in America, business recovery in New Orleans after Katrina, community resilience assessment, coastal resilience modeling using a coupled natural-human system approach. Lam has received top awards from within LSU (Distinguished Faculty, Rainmaker, Distinguished Research Master, and Outstanding Faculty Research Award), and outside LSU including Association of American Geographers’ (AAG) (Outstanding Contributions in Remote Sensing) and University Consortium on Geographic Information Science (UCGIS Fellow, The 2016 Inaugural Carolyn Merry Mentoring Award). Lam has coedited two books and authored and co-authored over 95 refereed articles. She has served as the Principal Investigor or Co-Principal Investigator of over 40 external grants. Lam has advised 5 post-doctoral associates, 17 PhDs, and 30 M.S. students.


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7110.2 - Cross-Scale Analysis of Sub-Pixel Variations in Digital Elevation Models


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