QUADS (http://www.metzgerwillard.us/quads/) is a web-based service for visualizing USGS quadrangles in Google Earth that provides an easy-to-use framework for retrieving georeferenced PDF topo maps from the USGS Store. QUADS also includes USGS, or USGSderived, overlays for grayscale and color shaded relief maps, topographic-bathymetric maps, black-and-white orthophotos, and urban areas color orthoimagery.