***** U.S.G.S. TOPOGRAPHICAL MAPS ***** (1992) 1) Coordinates in the United States can be determined with the use of a US Geological Map. (A LORAN-C System may also be used if you have access to one. See your local boat dealer for details.) 2) Information on these maps is available from: US Geological Survey Washington D.C. 20242 Or, call the Earth Science Center @ 1-800-872-6277 1-800-USA-MAPS 3) Maps can be ordered from: Map Distribution U.S. Geological Survey Box 25286, Federal Center Denver, Colorado 80225 Checks for map orders should be payable to: Department of the Interior - USGS The cost is $2.50 each. Add $1.00 for postage and handling if order is less than $10.00. These maps are also available at many local book and sporting goods stores. 4) The most common U.S.G.S Topographical Map is 7.5 X 7.5 Minutes. The standard scale is 1:24,000. Some states, including Massachusetts, New Hampshire, New York, and Vermont, also have 1:25,000 maps that use metric units. 5) The scale is 1" = 2,000 feet for 1:24,000 maps and 1 cm = 0.25 km for 1:25,000 maps. 6) Orthophotoquads are also available for many of the standard quadrangles along the East Coast. These are multicolored, distortion free, photographic image maps produced from aerial photographs. They have no contours and include only minimal cartographic treatment. ================================================================= ***** REFERENCE CODES FOR 7.5 MINUTE SERIES MAPS ***** SAMPLE REFERENCE CODE: 41072-H1-TF-024 DESIGNATION: AA BB CC DE FFF DESIGNATION CODE AA 41 41 Degrees Latitude (Quadrangle Minimum) BB 72 72 Degrees Longitude (Quadrangle Minimum) CC H1 Location within 1 X 1 Degree Square based on an 8 X 8 Grid. D T Type of map. T is for Topographical. E F Unit of measurement. F is for Feet. M is for Metric. F 024 Map Scale. 024 is for 1 : 24,000. 025 is for 1 : 25,000 ***** GRID SQUARE & OTHER DIMENSIONS ***** 1 Deg. Lat. = 69.05 mi./ 111.12 km/ 60.00 n-mi. 1 Deg. Long. @ 42 Degrees Lat. = 51.31 mi./ 82.58 km/ 44.59 n-mi. 0.001 Degree @ 42 Degrees Lat. = 365 ft Lat. & 271 ft Long. 1 Minute @ 42 Degrees Lat. = 6,076 ft Lat. & 4,515 ft Long. 1 Second @ 42 Degrees Lat. = 101 ft Lat. & 75 ft Long. NOTES: 1) Each Grid Square is 1 Deg. Lat. X 2 Deg. Long. or 69.05 mi. Lat. X 102.62 mi. Long. @ 42 Deg. Lat. 2) Each Sub-square is 2.5 Min. Lat. X 5 Min. Long. This is approximately 3 X 4 miles or 2.88 mi. Lat. X 4.28 mi. Long @ 42 Deg. Lat. (See Jan. 1983 QST pp 49 - 50) ================================================================= ***** COORDINATES FOR W1AW/ W1INF ***** Newington 41.715N 72.728W W1AW/ W1INF ================================================================= ***** DISTANCE & AREA CONVERSIONS ***** 1 km = 15,625/ 25,146 mi. (exact) = 0.621371192237 mi. 1 mi. = 25,146/ 15,625 km (exact) = 1.609344 km 1 n-mi. = 1.852 km (exact) 1 km = 1/ 1.852 n-mi. (exact) = 0.539956803456 n-mi. 1 mi. = 50,292/ 57,875 n-mi. (exact) = 0.868976241901 n-mi. 1 n-mi. = 57,875/ 50,292 mi. (exact) = 1.15077944802 mi. 1 n-mi. = 2,315,000/ 381 ft. (exact) = 6,076.11548556 ft. 1 km = 1,250,000/ 381 ft. (exact) = 3,280.83989501 ft. 1 Acre = 43,560 square feet (exact) NOTES: 1) 1 n-mi. is equal to 1 minute of latitude. 2) The distance between the Equator and a Pole is approximately 10,000,000 meters. (The original measurements were slightly in error and the standard meter has also has changed slightly. It is not exact.) NOTE: 1) Angle above Horizon = Arctan (Delta Elevation/ Distance) 2) Great Circle distances and headings are calculated by: cos D = sin A sin B + cos A cos B cos L cos C = sin B - sin A cos D/ cos A sin D Where: A = Your latitude in degrees. B = Latitude of other station in degrees. L = Your Long - other Long (algebraic difference). D = Path distance in degrees of arc. C = True bearing from North if sin L is positive. If sin L is negative, then true bearing is 360 - C. (From ARRL Operator's Manual)