My research is a combination of Computational Geometry and Computer
as applied to Geographic Information Systems (GIS). The main areas
currently under investigation are:
- DEM Error - many DEMs are constructed from less-than-perfect data, and along with the computations necessary to create the final surface, errors are inevitable. This research seeks to determine the severity of the error.
- Visualization - while many packages exist to view DEMs and other data, this research concentrates on viewing DEM error.
- Surface Reconstruction - creating a 3D (actually 2.5D) surface from 2D sources, such as
contour lines (isolines) or other sparse data arranged on a grid. The data is interpolated or otherwise used to create a digital elevation model (DEM). A DEM is useful for visualization and analysis of a particular region. Some of this work has been done in conjunction with
Wm. Randolph Franklin (Electrical, Engineering, and Systems Engineering Department, Rensselaer Polytechnic Institute)
- Interdisciplinary Research - I am in collaboration in other areas with researchers such as Mike Smith (School of Earth Sciences and Geography, Kingston University, London), John Grady (Department of Sociology, Wheaton College), and Michael Drout (Department of English, Wheaton College).
DEM and Error Visualization
A newer area of research is DEM terrain and error visualization. Traditional GIS have many capabilities to compute DEM error/uncertainty, but they require the user to go through many complex steps. Often, the result is simply a number or a 2D visualization.
This research seeks to make the process much easier and faster, as well as give a better error visualization.
Our current system, DEMView (previously DEMEV; see
Figure 1) has visualizations for relief,
raster height colors, slope, height classes,
curvature error, local elevation difference error, and
local curvature difference error. The difference errors are classified according to
The user can dynamically change the view, including the sun position,
vertical exageration, and so forth. In
addition, various statistics can be generated.
The latest innovation is a vertical "profile cutter" that allows one to
view a desired profile of two surfaces simultaneously
within the context of the 3D surface visualization.
Downloads (updated 7/26/2010)
Keep in mind that this is a prototype system, used for testing algorithms
and research ideas. It is not meant (yet, anyway!) to have all of
the functionality of a robust
commercial system. As such, it may not have all of the options available.
For example, the drop-down menus are currently in a woeful state; the magnifier
option has not yet been implemented.
The system was developed on Linux using an OpenGL-compatible graphics card.
On such a computer, response time is quite good with grids up to approximately
1200x1200. On a system without OpenGL optimization, one can expect poor performance.
robust across platforms is a problem we are currently working on.
The input for the system is only in ESRI ASCII Grid format.
demview1.2.gz - DEMView executable for Linux (309KB).
demview1.2.zip - DEMView executable for Windows XP (434KB).
Send email regarding execution problems and bugs to: mgousie(at)wheatonma.edu.
Gousie, M.B. The Case for 3D Visualization in DEM Assessment. In Developments in Spatial Data Handling: 15th International Symposium on Spatial Data Handling (Bonn, Germany, 2012). To appear.
Gousie, M.B. Focus + Context for Visualizing Uncertainty in DEMs. Poster presented at the IEEE Information Visualization Conference, 2011.
Gousie, M.B., and Smith, M.J. DEMView: 3D Visualization of DEM Error.
In Accuracy 2010, Proceedings of the Ninth International
Symposium on Spatial Accuracy
Assessment in Natural Resources and Environmental Sciences
(Leicester, UK, July 2010), N.J. Tate and P.F. Fisher, Eds.,
ISARA, pp. 165-168.
[Slides in ppt]
Gousie, M. B. and Milewski, S. A System for 3D Error Visualization and Assessment of Digital Elevation Models. In Proceedings of the 2007
IEEE International Geoscience and Remote Sensing
Symposium (IGARSS '07) (Barcelona, 2007),
Gousie, M. B. Digital Elevation Model Error Detection and Visualization. In The 4th Workshop on Dynamic & Multi-dimensional GIS (Pontypridd, Wales, UK, 2005), C. Gold, Ed., ISPRS, pp. 42-46.
Gousie, M. B., Williams, G., Agnitti, T., and
Doolittle, N. CompSurf:
An Environment for Exploring Surface Reconstruction Methods on a Grid. Computers
& Geosciences 29, 9 (2003), 1165-1173.
Source code: CompSurf v2.0 (Developed on Linux platform). See Figure 7 below.
Surface Reconstruction Animation
Surface Reconstruction Algorithms
Assume we start with a digitized contour map
of Mt. Washington, N.H. (Figure 2). The white space indicates areas where
elevations must be computed.
A traditional method for interpolating a surface
from contours is to use a partial differential equation that
models a thin plate being draped over the data points (Figure 3). This
yields the surface at right (colors go from blue=low elevation
to red=high elevation).
| Obviously, the surface in Figure 3 is not terribly smooth.
One way to
improve the surface is to create a thin plate approximation instead
of interpolation. This allows some of the original contour points
to vary slightly, creating a smoother, albeit less accurate, surface.
the reasons that the surface "scallops" in Figure 3 is because of the
difference in curvature of successive contours.
In our Intermediate Contour Method, we first
compute new contours in between the original data. The thin
plate approximation is then applied to the new data set, yielding a
measurably smoother result while preserving the accuracy of the
surface (Figure 4).
Following the idea that more data = better surface, we
find additional data in the Gradient Lines Method. In this algorithm,
"gradient paths" that follow the steepest slope from
contour to contour are computed. This creates a sort of mesh that can then be
filled in with various interpolating or approximating algorithms.
Here, we fill in the mesh with inverse distance weighting and finish
the surface with a Gaussian smoothing function (Figure 5).
It takes many iterations of the thin plate method
to completely fill in a regular grid of elevation points. This
animation shows how a sample contour map is filled in with a thin plate
approximation after intermediate contours are computed.
Smith, M.J., Rose, J., and Gousie, M.B. The Cookie Cutter: A Method for Obtaining a Quantitative 3D Description of Glacial Bedforms. Geomorphology 108 (July 2009), 209-218.
- Smith, M.J., Rose, J., and Gousie, M.B. A Method of Quantifying Subglacial Sediment Transport/Deformation. Poster presented at Geomorphology & Earth System Science, BGRG International Conference, Loughborough, UK, June 2006.
Gousie, M. B. and Franklin, W. R. Augmenting Grid-Based Contours to
Improve Thin Plate DEM Generation. Photogrammetric
Engineering & Remote Sensing 71, 1 (2005), pp. 69-79.
Gousie, M. B. and Franklin, W. R. Constructing a
DEM from Grid-based Data by Computing Intermediate Contours. In GIS
2003: Proceedings of the Eleventh ACM International Symposium on
Advances in Geographic Information Systems (New Orleans, 2003), E.
Hoel and P. Rigaux, Eds., pp. 71-77. [PostScript]
Franklin, R and Gousie, M. Terrain Elevation Data Structure Operations.
In 19th International Cartographic Conference & 11th General
Assembly of the International Cartographic Association (ICA)
Gousie, M and Franklin, R. Converting Elevation Contours to a Grid. In Proceedings,
Eighth International Symposium on Spatial Data Handling (1998), T.
Poiker and N. Chrisman, Eds., pp. 647-656. [PostScript][pdf]
Gousie, M. B. Contours to Digital Elevation Models: Grid-Based
Surface Reconstruction Methods. PhD thesis, Rensselaer Polytechnic
Institute, 1998. [PostScript][pdf]
Visualization of Social Stratification
This current research is being done in conjunction with
John Grady of
Wheaton College's Department of Sociology. The idea is to use metaphors to
create easy-to-use visualizations in order to see patterns in socio-economic
data gathered from the US Census. The Java applets allow the
user to compare different
social classes, ethnic backround, job type, and income in a dynamic way.
With the help of students, we have
created web-based prototypes using three different metaphors:
This is the original metaphor, where the center of a dart board represents
the highest income level and the rings representing progressively lower levels.
Each "hit" represents 160,000 individuals at that income level.
Click to run Target 1.0
Students Sarah Milewski and Chris Stuetzle, both of the Class of 2007,
implemented a newer applet of The Target which addressed some of the
shortcomings of the original version.
Click to run Target 2.0
In this metaphor, the goal is to climb to the peak of a mountain, where the
highest income levels exist. The different "mountains" can be moved or
stacked to more easily compare desired parameters. This is a nice improvement
over The Target.
This applet was implemented by Sarah Milewski '07 and Chris Stuetzle '07.
Click to run MountainClimber
Students Ben Burrage, Robby Grossman, Dave Machado, all from the Class of 2007,
implemented this metaphor, wherein equal-size boxes are stacked on top and
next to one another so as to allow easy comparisons. The more income, the
more a box is filled. Although this is perhaps a less-strong metaphor, the
regularity of each box makes it much easier to move about and stack to produce
data patterns. This implementation also has no inherent clustering effect
that both The Target and Mountain Climber have, as the area gets smaller as
the income level rises in both of the latter implementations.
Click to run CensusSquared
Gousie, M.B., Grady, J., Burrage, B., Grossman, R., Machado, D., Milewski, S., and Stuetzle, C. Using Metaphors in Dynamic Social Stratification Visualizations. In IV08: 12th International Conference on Information Visualization (London, 2008), IEEE, pp. 485-490.
- Gousie, M.B. and Grady, J. Targeting Social Stratification, presented at
the International Visual Sociology Association (IVSA) Annual Conference,
San Francisco, August 12, 2004. [Talk in HTML]
Undergraduate Research/Project Opportunities|
| There are some interesting research project or senior
thesis opportunities for interested students. In particular, I need
both a front and back end to my research code (described above). The
front end would involve creating a nice GUI for the program. The back
end would involve displaying the output graphically, allowing the user
to manipulate the resulting terrain. Nate Buggia '99 developed a simple
surface viewer (Figure 6), complete with lighting and shadows, among
other things for a COMP 399 - Advanced Computer Graphics course.
In the summer of 2001, Trevor Agnitti '02, Nick Doolittle
'03, and Greg Williams '03 tackled the problem. The resulting system
is shown in Figure 7. Trevor worked on the GUI, Nick worked on
surface reconstruction techniques, and Greg worked on the overall
object-oriented design and much of the graphics. The system allows a
researcher to view and evaluate two different surface reconstruction
techniques at the same time.
The group presented their work at the Consortium for
Computing in Small Colleges at Worcester State in April, 2002. The
abstract "A Surface Reconstruction Research Environment" appears in the
conference proceedings, The Journal of Computing in Small Colleges.
This work evolved into a major research paper (source code
available) in Computers & Geosciences.
Pat Sagui '04 completed a project in COMP 399 -
Advanced Computer Graphics in the fall of 2003. He modeled a scene
from a Lord of the Rings movie that includes many complex
graphics ideas, such as lighting, textures, and fog (Figures 8 and 9).
Steven Bowe '05 did some research work for me over the summer of
2004, funded by a Mars Fellowship. He worked on finding ways to
visually present errors found in digital elevation models.
He presented a poster of the work
at Wheaton's Academic Festival in 2005 as well as at the Consortium
for Computing Sciences in Colleges at Providence College in April, 2005.
His abstract appears in the proceedings as well (see below).
A nice GUI for a DEM error visualization system was implemented by Sarah Milewski '07 in the summer of 2006. This system gives traditional GIS users a quick way to check the validity of DEM data without going through many complex steps using traditional software. This ongoing research is shown in Figure 1.
Raleigh Upshur '10 worked on using a stencil buffer to zoom in on
portions of data in a scene, sometimes called ``focus with context." Current
research focuses on using this idea to view small places of interest on a
large-scale DEM while keeping the rest of the surface in context.
Computer Graphics (COMP 365) is usually a prerequisite in order to
work on these projects, but I do have others that do not require
graphics programming experience.
Relevant Student Publications/Presentations
Upshur, R. Viewing Three-Dimensional Terrain with Focus in Context.
Poster presented at the Fifteenth Annual Consortium for Computing Sciences
in Colleges Northeast Conference, April 2010.
Stuetzle, C. Computer Modeling and Visualization of Luminescent Crystals: The Role of Energy Transfer and Upconversion. Honors Thesis,
Wheaton College, 2007. See full text.
Bowe, S. Error Detection and Visualization in Digital Elevation
Models. In Journal of Computing Sciences in Colleges, Proceedings of the Tenth Annual CCSC Northeast Conference (2005), pp. 103-104.
Williams, G. An Autoscheduling Optimizer for Perl. Honors
Thesis, Wheaton College, 2003.
Williams, G., Doolittle, N., and Agnitti, T. A Surface Reconstruction
Research Environment. In Journal of Computing in Small Colleges,
Proceedings of the Seventh Annual CCSC Northeast Conference (2002),
- Trying Technology on for Size. Part of the President's Commision meeting, Wheaton College, April 2010.
- Math Connections in Computer Science. Panel discussion with Wilkens, et al. at CCSCNE, April 2009. In Journal of Computing Sciences in Colleges, Proceedings of the Fourteenth Annual CCSC Northeastern Conference (2009), pp. 57-61.
- How Good Is Google Earth? Department of Computer Science Seminar, Siena College, Albany, NY, October 2007.
- Can You Trust Google Earth? Department of Mathematics and Computer Science Seminar Series, Wheaton College, October 2007.
- Math for Non-Mathers: Using Math and Programming in Everyday Life. Wheaton College Faculty Lunch Series, March 2, 2005.
- The Role of Digital Logic in the Computer Science Curriculum.
Panel discussion with Hoffman, et al. at CCSC-NE, April 23, 2004. In Journal
of Computing Sciences in Colleges, Proceedings of the Ninth Annual
CCSC Northeastern Conference (2004), pp. 5-9.
- Thunderstorms, Orange Slime, and Boiling Mud, with B.
Dyer and G. Collins. Part of the Puzzles in Science series,
Wheaton College, 2003.
- Implementing the Architecture, Assembly Language and
Operating Systems Components of Curriculum 2001. Panel discussion
with Wilkens, et al. at CCSC-NE, April 25, 2003. In Journal of
Computing Sciences in Colleges, Proceedings of the Eighth Annual
CCSC Northeastern Conference (2003), pp. 118-122.
- Building a Surface Reconstruction Research Environment.
Williams College Computer Science Colloquium, April 5, 2002. [Slides in PostScript][Slides
- Making a Mountain out of a (Math) Model. Wheaton College
Faculty Lunch Series, October 26, 2000.
- Improving Terrain Reconstruction on a Grid. Williams
College Computer Science Colloquium, 1998.
GIS and CG Links (Updated 7/26/2010)
- Association for Computing Machinery. A valuable resource is:
- ASPRS - the imaging
and geospatial information society. Tables
of contents for Photogrammetric Engineering & Remote
- ISARA - International
Spatial Accuracy Research Group; sponsors the bi-annual Accuracy symposium.
- IEEE - The Institute of
Electrical and Electronics Engineers. Online tables of contents:
- Journal of Maps - on-line journal started by Mike Smith at Kingston University, England.
- Computers & Geosciences - latest published volume complimentary.
- International Geographical Union: Commission on Geographical
Information Science. This organization holds the annual Symposium on
Spatial Data Handling. The site also has a nice list of GIS journals.
- International Journal of Geographical Information Science.
There are various places to get USGS data and GIS information,
shuttle topography mission - the SRTM home page.
- Census Bureau Geography
- shows all US Census Bureau products, maps, and resources.
- USGS Home Page - has
general information and links to SDTS-formated DLG data.
Data Center - access to USGS 1:250,000 scale DEMs and
1:2M/1:100K DLGs, among others. Some of my own test data was retrieved
from this site.
- Bureau of Land Management
(BLM) home page - access to GIS information and MetaData.
- geodata.gov - another
source of US data, not limited to maps.
- Environmental Protection
Agency - contains some GIS and mapping related information,
including some data here.
- free maps of just about anyplace in the US. Also offers commercial
- Earth Science and
Geology Links - from the Illinois State Geological Survey, this
page has a large number of links to many interesting GIS related sites,
all indexed by category.
- manifold.net -
GIS, mapping, database, and 3D software; also a source of map data.
- look at satellite imagery for anyplace in the U.S. and some areas of the world.
- Trails.com -
commercial topo map site. These are not data maps, but you can look at
topos from just about any place in the U.S.
Some Computational Geometry (CG) sources: