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From approximately 1947–1992, the USGS produced the 7.5 minute series, with each map covering an area one-quarter of the older 15-minute quad series, which it replaced. [1] A 7.5 minute quadrangle map covers an area of 49 to 70 square miles (130 to 180 km 2 ). [ 2 ]
Topographic maps are also commonly called contour maps or topo maps. In the United States, where the primary national series is organized by a strict 7.5-minute grid, they are often called or quads or quadrangles. Topographic maps conventionally show topography, or land contours, by means of contour lines.
Each map was bounded by two parallels and two meridians spaced 15 minutes apart—the same area covered by four maps in the 7.5-minute series. The 15-minute series, at a scale of 1:63,360 (one inch representing one mile), remains the primary topographic quadrangle for the state of Alaska (and only for that particular state).
DOQs produced by the USGS cover an area measuring 7.5-minutes longitude by 7.5-minutes latitude (the same area covered by a USGS 1:24,000-scale topographic map, also known as a 7.5-minute quadrangle) or 3.75-minutes by 3.75-minutes.
Date/Time Thumbnail Dimensions User Comment; current: 20:09, 21 March 2023: 584 × 1,426 (640 KB): Jengod: Uploaded a work by USGS from USGS 7.5-minute image map for Point Arguello, California Point Pedernales ...
During the registration process, prospective volunteers submitted a list of the 7.5 minute quadrangle maps on which they wished to work. Once accepted into the project, volunteers received their assignment and 1:24,000 scale topographic map of their quad. While there was no deadline for completing maps, the project's administrators preferred ...
The largest (both in terms of scale and quantity) and best-known topographic series is the 7.5-minute or 1:24,000 quadrangle. This scale is unique to the United States, [citation needed] where nearly every other developed nation has introduced a
Notes: This area can also be found on the following quadrangles: King and Queen Court House, New Kent, Truhart, West Point (all 7.5 minute series). Relief shown by contours and spot heights. "Contour interval on land 20 feet, with the 10 foot contour added; datum is mean sea level; contour interval off shore 20 feet, with 5 and 10 foot contour ...