USGS QUADRANGLES IN GOOGLE EARTH

Transcription

1 USGS QUADRANGLES IN GOOGLE EARTH By Thomas G. Davis 1, PhD, PE, PLS and Rollins Turner 2, PhD INTRODUCTION QUADS ( is a web-based service for visualizing USGS quadrangle boundaries in Google Earth that provides an easy-to-use framework for retrieving georeferenced PDF (GeoPDF) topo maps. QUADS also includes USGS overlays for topographic-bathymetric and hydrographic maps. QUADS The principal component of QUADS is a Google Earth network link that plots approximate USGS quadrangle boundaries (Fig. 1) and provides direct access to 122,992 GeoPDF maps (TerraGo 2015, USGS 2015e), including scans of the last historical paper map in all available grid sizes. All quadrangle balloons (Fig. 2) contain name, primary state, nominal grid size, scale, imprint year, and file size information with a link to the corresponding GeoPDF map. Use the All maps with this name link to search for older historical maps or newer current maps in the USGS Topographic Map Collection (USGS 2015d). See USGS (1995) for a discussion of various map series and USGS (2000) for a list of topographic map symbols. Quadrangles are categorized by map series (Table 1) and collected in grid-size subfolders. Coverage includes the conterminous United States, Alaska, Hawaii, Puerto Rico, the US Virgin Islands, Guam, American Samoa, Micronesia, Palau, the Northern Mariana Islands, and portions of Canada. The user is prompted to zoom in if there are more than 1000 quadrangles in view. If there are no quadrangles within the viewer bounding box, the Search Results network link will contain an empty folder named OutOfRange. GeoPDFs were initially produced by the US Army Corps of Engineers Topographic Engineering Center, currently known as the US Army Geospatial Center, using existing digital raster graphics (DRGs). Traditional topographic GeoPDFs produced by the USGS are created from high-resolution scans of paper maps and compose the Historical Topographic Map Collection (HTMC) (USGS 2015b). The USGS is engaged in an ongoing effort to scan all existing paper maps. The current electronic map series, US Topo (USGS 2015f), is created by the USGS National Geospatial Technical Operations Center from The National Map (TNM) data including color orthoimagery. The QUADS database and this document will be updated periodically to reflect changes in the USGS map offering. 1 Metzger + Willard, Inc., 8600 Hidden River Parkway, Suite 550, Tampa, FL tdavis@metzgerwillard.com 2 Computer Science and Engineering, University of South Florida, Tampa, FL, retired. rollins@tampabay.rr.com February of 7

2 Table 1. Topographic Map Series Series Source Count US Topo The National Map 55,818 HTMC Historical Topographic Maps 67,174 QUADS is similar in function to the Map Locator (USGS 2012), a Google Maps application that runs in the user's web browser. The Locator is an outstanding browser application but lacks the robust user interface and flexibility of Google Earth. Figure 1. USGS Quadrangles February of 7

3 Refresh Mode The Refresh Mode network links provide a uniform mechanism to control the Search Results and Overlays network links. When Refresh Mode is Manual, the contents of the network links are effectively frozen, allowing the user to pan and zoom without prompting a network link refresh. This is particularly useful for inspecting overlays or gaining an overview of network link contents. To initiate a network link: 1. Position the area of interest (AOI) in the viewer. 2. Check the Search Results network link (Fig. 1) to display quadrangle placemarks and boundaries, or check one of the Overlays network links (Fig. 3) to display USGS ground overlays. 3. On subsequent uses, reposition the AOI and ensure that the network link is checked and selected. When Refresh Mode is Automatic, search results are refreshed two seconds after camera movement stops. When Refresh Mode is Manual, choose Refresh from the Edit menu, or right-click and select Refresh in the context menu. The Manual and Automatic network links may be used to stop and start refreshes for the Search Results and Overlays network links. The default refresh mode is Automatic. To stop refreshes, check Manual; to restart refreshes, check Automatic. Canceling an edit of network link properties will disable mode selection for that particular network link. Figure 2. Quadrangle Balloon February of 7

4 Overlays Overlay layers (Table 2) are implemented as network links that retrieve multiresolution images from an OpenGIS-conformant Web Map Service (WMS) (OGC 2006) or via a Representational State Transfer (REST) export. All requests are directed first to the QUADS server where bounding box coordinates are conformed to service requirements before being passed to the service provider. Table 2. Overlay Layers Layer 1 Resolution 2 Service 3 Extent 4 TOPO! 5 2 REST 6 US 7 TNM DRG 8 2 WMS 9 US/PR/VI 10 Hydrography 11 < 1 REST 12 CONUS 13 1 Overlays network link name 2 Maximum resolution (meters per pixel) 3 Service type 4 Service coverage area 5 National Geographic TOPO! series (Esri 2015) (Fig. 3) 6 USA Topo Maps server (Esri 2014) 7 Conterminous US, Alaska, and Hawaii 8 USGS topographic-bathymetric Digital Raster Graphics (DRG) (Fig. 4) 9 TNM DRG server (USGS 2015a) 10 Conterminous US, Alaska, Hawaii, Puerto Rico, and the US Virgin Islands 11 National Hydrography Dataset (NHD) (USGS 2014) (Fig. 5) 12 EPA Office of Water NHDPlus server (EPA 2015) 13 Conterminous US When the viewer bounding box is outside the coverage area, requests are not forwarded to the service provider, and the associated Overlays network link will contain an empty folder named OutOfRange. See USGS (2015c) for other layers available from the USGS. February of 7

5 Figure 3. National Geographic TOPO! Figure 4. USGS Digital Raster Graphic February of 7

6 Figure 5. National Hydrography Dataset CONCLUSION QUADS provides user-friendly, graphically oriented access to a wealth of publicly available geospatial information maintained by the USGS. Metzger + Willard, Inc. is pleased to make QUADS freely available to anyone having Google Earth installed on a computer with an Internet connection. ACKNOWLEDGMENTS The authors wish to thank the following individuals for their help in implementing or testing QUADS: Jeff Wendel and Andy Orona, USGS; Scott Brown, PLS, George F. Young, Inc.; and Kemp Morris, PSM, Morris Surveying, Inc. Special thanks are extended to Steve Skelton, USGS. REFERENCES EPA (2015). "WATERS Mapping Services." ( Esri (2015). "USA Topo Maps." ( Esri (2014). "USA Topo Maps (MapServer)." ( February of 7

7 Open Geospatial Consortium (2006). "OpenGIS Web Map Server Implementation Specification." ( TerraGo Technologies (2015). "TerraGo Toolbar." ( United States Geological Survey (2015a). "Digital Raster Graphics (ImageServer)." ( RG_SCALE/ImageServer/) United States Geological Survey (2015b). "Historical Topographic Maps." ( United States Geological Survey (2015c). "The National Map Small-Scale Web Services." ( United States Geological Survey (2015d). "US Topo and Historical Topographic Map Collection." ( United States Geological Survey (2015e). "US Topo Map and Historical Topographic Map Users Guide." ( United States Geological Survey (2015f). "US Topo Quadrangles." ( United States Geological Survey (2014). "National Hydrography Dataset." ( United States Geological Survey (2012). "Map Locator." ( United States Geological Survey (2000). "Topographic Map Symbols." ( United States Geological Survey (1995). "USGS Maps Booklet." ( February of 7