At the February 28 Lunch ‘n Learn seminar, Bill Guthe, David Potere, Bethany Bradley, Wangyal Shawa presented GIS at Princeton: Gathering Knowledge from Satellite Images. Bill Guthe began the session by describing GIS and Remote sensing opportunities at Princeton.
David Potere of Princeton’s Office of Population Research explained that the earth is encircled today by a rapidly expanding network of satellite remote sensing platforms. Collectively, this international Earth Observation System takes a complete image of the planet every day, transmitting terabytes of data to dozens of ground-Earth stations scattered across all the continents.
He noted that efforts are underway to link together all of the earth observation systems. There are currently more than 50 civilian satellites looking at our planet, and the ownership is rapidly becoming more distributed with new “birds” being launched by more than a dozen countries, notably India, China, and Korea. In just the past five years, the satellites are offering important new capabilities.
These satellites no longer record just the familiar reds, greens, and blues of visible light–they image ever wider swaths of the full electromagnetic spectrum, peering out into the infrared, gathering emitted light from our cities at night, and transmitting microwaves that penetrate the densest cloud cover.
He emphasized that there are four frontiers for earth observation: Spatial Resolution, Temporal Resolution, Spectral Resolution, and New Energies.
Spatial Resolution attempts to resolve the surface of the earth. The finest resolution of Google Earth, for example, goes down to one meter. And so, we can trivially see our own homes and swimming pools. Such imagery has been available for the United States approximately 15 years. It is now also available for most the earth. One of the challenges here is that the file sizes for 1 meter imaging of the earth are very large and increasing at the rate of multiple terabytes per day. Building algorithms to deal with that kind of data volume represents a real challenge.
Temporal resolution cares more about how often the earth is observed. The finer the resolution, the less often the entire earth will be scanned. Satellites with fine resolution might examine Princeton once every two weeks. Other satellites with a courser resolution might examine every place on earth once or twice a day, a very useful asset for those observing climate change.
Spectral Resolution involves the number of colors we can see. We are no longer limited to the visible spectrum. We can now record the near and far infrared. As a result, for example, we can judge the relative health of vegetation.
And some new satellites are looking at totally new energies. By clicking on the terrain button within Google Earth, you can drape color imagery on top of a 3-D map of the earth. And there are wonderful images of the earth at night showing night-time emitted light sources from settled areas.
Bethany Bradley, a post-doctoral student in the Woodrow Wilson School, has used GIS, remote sensing tools, and the data derived from such satellites to study invasive plant species in the Western United States. In a case study of “cheatgrass,” she illustrated how she determined the extent of its proliferation, and how the data permitted her to view the change in growth patterns, hypothesize on the cause of its spread, and the likely areas for future infestation.
By using the different satellites to identify the spread of cheatgrass, and by mapping changes in urbanization, land use, the development of roads, as well as rainfall patterns, she was able to determine that road construction encouraged the spread of cheatgrass. She showed GIS images of rainfall patterns and cheatgrass growth to illustrate the impact of rainfall on sustaining the invasive species and to identify likely areas for its spread.
GIS and Remote Sensing classes on campus:
There are numerous opportunities on campus to learn more about GIS and remote sensing. You can register for these short afternoon training classes:
- Introduction to Geographic Information Systems: what is ArcGIS
- Geographic Information Systems II: common tools in ArcGIS
- Incorporating U.S. Census data into ArcGIS
- Making Maps and Presentations using ArcMap in ArcGIS
- Exploring Google Earth
- Running Modelbuilder and Scripts in ArcGIS
These classes are offered twice or more each semester in Training Room A-6-D of Firestone Library. You can schedule such sessions for particular groups of students as part of a course. You can also take Virtual Campus GIS classes at no charge from ESRI. These classes generally take six to eight hours to complete. Contact Wangyal Shawa to sign up for:
- Learning ArcGIS 9
- Learning ArcGIS 9 3D Analyst
- Learning ArcGIS 9 Spatial Analyst
Geographic Information System and Remote Sensing Software:
The University provides support for Environmental Systems Research Institute ArcGIS 9.x and Leica Geosystems Imagine 9.1.
ESRI’s ArcGIS supports data viewing, analysis, map production, interactive displays for both vector and raster data. The University has a limited site-wide license.
Leica Geosystems Imagine 9.1 offers image processing and analysis. You can use it to extract vector features from satellite images and digital air photos and process multi-band images to find classes of vegetation, soils, and other land features. The basic software is also available without charge. Contact Bill Guthe for access to the software.
Presentations and a podcast are available on the Lunch ‘n Learn web site.