Land Cover Change Maps
 

 
Detecting Landcover Change
The Center for Earth and Planetary Studies has an extensive archive of Landsat Thematic Mapper (TM) data. We are exploring methods of using these data for detecting landcover change in the Washingotn area. The objective is to identify simple methods for locating large areas undergoing change from unpaved to paved landcover.

Methods
Because satellite-derived vegetation indicies can identify areas lacking vegetation, they can be used to describe the morphology of urban features. A normalized difference vegetation index (NDVI) image was created using TM bands 3 and 4. A ratio image of TM bands 5/1 was then used to separate paved surfaces from bare ground and fallow agricultural fields. TM band 4 was used to mask water bodies. Threshholds and a three-step modeling procedure were applied to these images. Image processing and modeling was performed using PCI software.

Results
The images listed on the previous page show where paved surfaces expanded between 1993 and 1997. Large areas that have undergone landcover change from unpaved to paved landcover are visible. The images show that the amount of paved landcover increased by about 5% over that time period.

Several large projects are visible in the images: the Dulles Greenway and development around Ashburn, VA, a new football stadium in Maryland, and construction of the Metro green line in Prince George's County and southeast D.C.

More Information
This work was the subject of a presentation at the meeting of the Association of American Geographers. Click here to email your questions.

These are preliminary results. Accuracy assessments have not been performed and the results have not been subject to scientific peer review. Stay tuned for future developments.

Land Cover Change Maps



 


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Revised: April 2, 2001 (jh)
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