Digital orthophotos and DEMs combat closed landfills

A landfill is a complex group of distinctly constructed and differently covered cells, sometimes constructed on top of each other. Early recognition of potential problems could bring about important cost savings and reduction in environmental degradation because repairs could be made before the water infiltration problem requires extensive (and expensive) remedial measures. Since a closed landfill no longer generates income, the potential economies of a remote sensing method of postclosure monitoring of cover performance are attractive even if it has some limitations and uncertainty. This article highlights how a DEM, a three dimensional array of positions and elevations, can be used to derive drainage and topographic maps, and rectify and correct relief displacements of scanned aerial photos to create orthophotography. With the improvement in speed and affordability of computers, the lower cost and higher resolution of scanning aerial photos, and the development in DEM extraction algorithm, this task can be achieved efficiently and economically.