Collecting forest canopy data from atop Mt. Eagle, St. Croix’s highest point
UVI Students collect field date at one of 250 GPS waypoints. This point is a mixed pasture with guinea grass (Panicum maximum) and tan-tan (Leucaena leucocephala). Data from the points are used to create classified maps from Landsat satellite images.
Aerial view of Frederiksted, St. Croix showing a combination of all 5 cover-classes and how they tend to be clustered together. Water in the foreground, developed on the right side, grass (both in pastures and a baseball park) secondary forest patches in the lowlands and forest on the hilltops.
|Forest and Maps|
The Agroforestry Program at UVI-AES conducts research that includes mapping land-covers of St. Croix such as forests, agriculture and development. This work is often referred to as Land-use, Land-cover change (LULCC) research. We accomplish this using Global Positioning System (GPS) units, Geographic Information systems (GIS) software (ArcGIS 9.2 and ERDAS Imagine) and digital images such as satellite images and aerial photographs.
From 2004-2008 we conducted a project that divided the island of St. Croix into 5 land cover classes and showed how the island changed over a 10 year period. We used Landsat satellite images from 1992 and 2002. We collected extensive field data at 250 random points across the island. The point data was used both for classification and for accuracy assessment of the final product. The results include classified maps of St Croix for 1992 and 2002 (figures 1&2). By digitally overlaying the two maps we also identified the areas of the island that experience the greatest change during that time period. Those results are expressed as deforestation (red) and reforestation (green) in figure 3.
More detailed information on the methods and results of this project will be available on this site in the near future. Contact us if you would like to use some of these maps or some of our supporting data in your own project.
Figure 1. Classified map of St. Croix for 1992. Dark green-forest, light green-secondary forest, yellow-grass, grey-developed, blue-water.
Figure 2. Classified map of St. Croix for 2002. Dark green-forest, light green-secondary forest, yellow-grass, grey-developed, blue-water.
Figure 3. Primary change areas for the 10 year period combined with a topographic image. Red signifies areas of forest loss and green identifies areas of forest gain.