National Geographic : 1993 Sep
Scientists harvest data from a cleared piece of land Seen in its true colors, the farmland of Gal lon Jug, an unmistak able shape on the remote-sensing images, appears raw and naked 0 100 P MILES NGSCARTOGRAPHIC DIVISION Area co in the midst of thick forest. The scientists chose Gallon Jug-here seen looking south-so they could compare instrument readings of Yucatn 'eninsu Ia veredvby radarmosaic on page 119 MEXICO elje City ,an the natural landscape with those of altered areas such as cattle pasture. They soon con cluded that no sensor by itself provides a com plete picture. The radar, for instance, could not distinguish between a freshly plowed field and a field with sprouting corn; scientists required the spectral data from AVIRIS to spot the vegetation. To the naked eye the fields reveal a troubled history. The owner, fearing a repeat of his first year's experience when soggy fields reduced the corn crop, scraped high spots to fill in low ones. In GUATEMALA HONDURAS doing so he bared large patches of infertile lime stone. Ideally, farmers could take advantage of remote-sensing images to identify areas for farming that would be more easily worked and have less impact on the environment. The TREE study area-a region of forest, swamp, and savanna in northwestern Belize-is part of the most exten sive rain forest left in Central America. It is not virgin forest. To feed a large population, the Maya cleared most of this area, which is filled with signs of their pres ence. Sponsors of the TREE project were curi ous as to whether the airborne sensing devices could detect undiscovered ruins beneath the canopy. So far, any ruins have stayed hidden.