WorldWide Drilling Resource

Notes from the Groundwater Guy by Thomas E. Ballard, P.G., C.H.G. Southeast Hydrogeology, PLLC Tools of the Trade: Historical Topographic Maps Why historical topographic maps? The U.S. Geological Survey (USGS) started their topographic map program in 1879, with the first maps produced in 1884. Over the years, the USGS has produced topographic maps at different scales and for different uses, with maps being updat- ed with new features as development dictated. Many times, we can see subtle topographic features which can be obscured by development over the years. Older topographic maps may include details useful in prospecting for water, like springs or other features which may not show up on current topographic maps. Comparing topographic maps of different vintages can often help with geologic interpretation of various areas, based on the relationship of geology to topographic features - especially structures - which can be important in siting productive wells. Historical topographic maps provide one more item in our toolbox of groundwater e xploration resources. As mentioned in m y July 2018 WWDR article, historical topographic maps are available in four formats on the TopoView website : https://ngmdb.usgs.gov/topoview/ 1. GeoPDF - This is the standard format for digital topographic maps from the USGS. Maps are in a PDF format which can be read by any PDF reader, but also are georeferenced so they can be directly imported into geographic infor- mation system (GIS) software. The GeoPDF format provides accurate map scale, and is the most faithful digital representation of the original paper topo- graphic maps. 2. GeoTIFF - These files are a compressed, 300-dpi TIFF image format, with embedded georeferencing information so the map can be used directly in GIS software. Like the GeoPDF, GeoTIFFs are generated at true scale, allowing users to plot the map at the intended map scale in cases where a hard copy is needed. 3. JPEG - High-resolution JPEG format files are useful for getting a quick view of the map to find place names, or simply explore the map area without the need for downloading a large file. 4. KMZ - The KMZ format is used for displaying the maps in Google Earth. These files are georeferenced so they will open in Google Earth in the correct location, allowing the user to add overlays of geology and other maps which can aid in exploration for water. Different formats are useful in different cases or in differ- ent software programs. The GeoPDF is going the be the most useful format in most circumstances. Current t opographic maps are available at the USGSNationa l Map website: https://nationalmap.gov/ustopo/index.html Tom Tom Ballard may be contacted via e-mail to michele@worldwidedrillingresource.com New & Used Bits, HDD Bits & Tools, Drag Bits & Wings, Bolt-On Drag Bits, Reverse Circulation Tools, Hole Openers, Claw Bits, Stabilizers, Subs, Custom Tooling & Welding, Hammer Bits, Drill Collars, Pipe Wipers, and Drill Pipe. Office: (661) 834-4348 Rod Henderson / Eran Henderson 661-201-6259 • 661-330-0790 sales@bitcobits.com www.bitcoinc.us 45 WorldWide Drilling Resource ® SEPTEMBER 2018 EXB In Britain’s 2001 census, 390,000 people listed “Jedi” as their religious affiliation.