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USGS QUADRANGLES IN GOOGLE EARTH

By Thomas G. Davis1, PhD, PE, PLS and Rollins Turner 2, PhD

INTRODUCTION QUADS (http://www.metzgerwillard.us/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, hydrographic, and shaded relief 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 122,353 GeoPDF maps (TerraGo 2014, USGS 2014a), 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 2014e). 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 2013b). The USGS is engaged in an ongoing effort to scan all existing paper maps. The current electronic map series, US Topo (USGS 2014f), 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 33637.

E-mail: tdavis@metzgerwillard.com 2 Computer Science and Engineering, University of South Florida, Tampa, FL, retired.

E-mail: rollins@tampabay.rr.com

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Table 1. Topographic Map Series

Series Source Count

US Topo The National Map 55,178

HTMC Historical Topographic Maps 67,175 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

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Refresh Mode The Refresh Mode network links provide a uniform mechanism to control the Search Results and Layers 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 Layers 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 Layers 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

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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

Layer1 Resolution2 Service3 Extent4

TOPO! 5 2 REST6 USGS TNM7

TNM DRG 8 2 WMS9 USGS TNM10

Hydrography11 < 1 REST12 CONUS13

GrayRelief 14 10 WMS15 USGS NED16

ColorRelief 17 100 WMS18 NationalAtlas10

1 Layers network link name 2 Maximum resolution (meters per pixel) 3 Service type 4 Extents subfolder name 5 National Geographic TOPO! series

(Esri 2014a) (Fig. 3) 6 USA Topo Maps server (Esri 2014b) 7 Conterminous US, Alaska, and Hawaii 8 USGS topographic-bathymetric Digital

Raster Graphics (DRG) (Fig. 4) 9 TNM DRG server (USGS 2014b) 10 Conterminous US, Alaska, Hawaii, Puerto

Rico, and the US Virgin Islands 11 National Hydrography Dataset (NHD)

(USGS 2014c) (Fig. 5)

12 EPA Office of Water (OW) NHDPlus server (EPA 2014)

13 Conterminous US (in USGS NED folder) 14 National Elevation Dataset grayscale

shaded relief map (USGS 2006) (Fig. 6) 15 Earth Resources Observation and Science

(EROS) support server (USGS 20013a) 16 Conterminous US, portions of Alaska,

Hawaii, American Samoa, Guam, and other US territorial islands

17 National Atlas color shaded relief map (National Atlas 2013a) (Fig. 7)

18 National Atlas web map server (National Atlas 2013b)

Coverage graticules may be displayed by checking the corresponding Extents subfolder. When the viewer bounding box is outside the coverage area, requests are not forwarded to the service provider, and the associated Layers network link will contain an empty folder named OutOfRange. Relief maps (Figures 6 and 7) achieve a three-dimensional appearance by determining an intensity for each pixel based on the terrain gradient and illumination from a light source in the northwest. See USGS (2014d) for other layers available from the USGS.

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Figure 3. National Geographic TOPO!

Figure 4. USGS Digital Raster Graphic

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Figure 5. National Hydrography Dataset

Figure 6. National Elevation Dataset Grayscale Relief

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Figure 7. National Atlas Color Relief

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 (2014). "Mapping Services."

(http://water.epa.gov/scitech/datait/tools/waters/services/mapping_services.cfm) Esri (2014a). "USA Topo Maps." (http://goto.arcgisonline.com/maps/USA_Topo_Maps) Esri (2014b). "USA Topo Maps (MapServer)."

(http://server.arcgisonline.com/ArcGIS/rest/services/USA_Topo_Maps/MapServer) National Atlas of the United States (2013a). "Color Shaded Relief of the United States."

(http://nationalatlas.gov/mld/csr100i.html)

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National Atlas of the United States (2013b). "National Atlas Web Map Services Introduction." (http://www.nationalatlas.gov/infodocs/wms_intro.html)

Open Geospatial Consortium (2006). "OpenGIS Web Map Server Implementation Specification." (http://portal.opengeospatial.org/files/?artifact_id=14416)

TerraGo Technologies (2014). "TerraGo Toolbar." (http://www.terragotech.com/products/terrago-toolbar)

United States Geological Survey (2014a). "About GeoPDF Maps." (http://store.usgs.gov/locator/about_digital_maps.html)

United States Geological Survey (2014b). "Digital Raster Graphics (ImageServer)." (http://raster.nationalmap.gov/arcgis/rest/services/Scanned_Maps/USGS_EROS_DRG_SCALE/ImageServer/)

United States Geological Survey (2014c). "National Hydrography Dataset." (http://nhd.usgs.gov/)

United States Geological Survey (2014d). "The National Map - Service Endpoints." (http://viewer.nationalmap.gov/example/services/serviceList.html)

United States Geological Survey (2014e). "US Topo and Historical Topographic Map Collection." (http://geonames.usgs.gov/pls/topomaps/)

United States Geological Survey (2014f). "US Topo Quadrangles." (http://nationalmap.gov/ustopo/)

United States Geological Survey (2013a). "Earth Resources Observation and Science." (http://eros.usgs.gov/)

United States Geological Survey (2013b). "Historical Topographic Maps." (http://nationalmap.gov/historical/)

United States Geological Survey (2012). "Map Locator." (http://store.usgs.gov/b2c_usgs/usgs/maplocator/%28uiarea=2%29/.do)

United States Geological Survey (2006). "National Elevation Dataset." (http://ned.usgs.gov/)

United States Geological Survey (2000). "Topographic Map Symbols." (http://pubs.usgs.gov/gip/TopographicMapSymbols/topomapsymbols.pdf)

United States Geological Survey (1995). "USGS Maps Booklet." (http://pubs.usgs.gov/gip/usgsmaps/usgsmaps.html)