DGPS
From HFUnderground
The Differential Global Positioning System (DGPS) transmits correction information that improves the accuracy of the GPS system, from 15 meters to as good as 10 cm. These transmissions are in the 283.5-325.0 kHz band, and are interesting DX targets.
Stations in the United States and Canada typically transmit on 1 kHz channel steps, while those outside of North America can also use 0.5 kHz channels. Transmissions are at 100 or 200 baud, using MFSK. DGPS Data packets contain a 10 bit ID. This ID is not unique, but using a combination of the ID along with the frequency and baud rate allows the specific station to be identified. Data transmissions are continuous, so it is possible to receive many messages per minute from strong stations, as well as the occasional message from more distant or weaker stations. DGPS stations can be used as propagation beacons, observing when messages from the various stations are being received.
Software to decode DGPS includes Amalgamated DGPS which is available for Windows and Macintosh computers. Amalgamated DGPS can decode the entire DGPS band from I/Q recording files made by various popular SDR programs. It can also decode portions of the band from either WAVE audio files, or from live audio via a sound input.
The following is the output from Amalgamated DGPS from a series of I/Q recording files, covering approximately a 24 hour period, as received in Maryland, USA. The list is sorted by the number of received messages (Count) from each station. Many DX stations were received, including from the West Coast and Panama. DGPS stations from Alaska, as well as Europe, have also been received at this location.
Count ID ref1 ref2 kHz Baud City Country Lat Lon km Deg 3 816 032 033 304.0 100 Aransas Pass, TX United States 27.842 -97.065 2,269 241 7 907 304 305 320.0 200 Richmond, BC Canada 49.114 -123.183 3,753 302 23 881 262 263 302.0 100 Point Loma, CA United States 32.677 -117.25 3,666 271 32 886 272 273 287.0 100 Fort Stevens, OR United States 46.208 -123.96 3,834 297 46 828 246 247 301.0 100 Angleton, TX United States 29.301 -95.484 2,046 241 62 946 344 345 299.0 200 Rigolet, NL Canada 54.25 -58.5 2,127 34 83 918 310 311 286.0 200 Wiarton, ON Canada 44.75 -81.117 656 330 498 919 308 309 306.0 200 Cardinal, ON Canada 44.783 -75.417 579 12 806 936 332 333 319.0 200 Point Escuminac, NB Canada 47.075 -64.8 1,278 46 1037 934 336 337 307.0 200 Fox Island, NS Canada 45.361 -61.097 1,442 59 1513 814 028 029 293.0 200 English Turn, LA United States 29.886 -89.947 1,608 231 1676 972 901 902 302.0 200 Miraflores Panama 8.993 -79.585 3,425 185 2364 927 316 317 309.0 200 Lauzon, QC Canada 46.821 -71.165 920 29 2464 937 330 331 298.0 200 Hartlen Point, NS Canada 44.583 -63.45 1,238 60 4590 940 338 339 315.0 200 Cape Race, NL Canada 46.661 -53.075 2,076 60 5094 944 342 343 310.0 200 Cape Norman, NL Canada 51.509 -55.831 2,091 44 5337 830 100 101 296.0 100 Wisconsin, Point WI United States 46.708 -92.025 1,444 308 7622 809 018 019 289.0 100 Cape Canaveral, FL United States 28.467 -80.554 1,292 196 7861 836 112 113 292.0 200 Cheboygan, MI United States 45.656 -84.475 901 320 9198 971 903 904 307.0 200 Gatun Panama 9.261 -79.937 3,398 186 10242 839 118 119 322.0 100 Youngstown, NY United States 43.239 -78.972 427 338 15109 869 168 169 290.0 200 Louisville, KY United States 38.018 -85.31 745 258 15927 925 320 321 313.0 200 Moise, QC Canada 50.202 -66.119 1,443 32 16015 865 160 161 320.0 200 Millers Ferry, AL United States 32.095 -87.397 1,262 231 16196 864 158 159 317.0 200 St Paul [Alma], MN United States 44.306 -91.906 1,333 297 16885 935 334 335 312.0 200 Western Head, NS Canada 43.993 -64.67 1,124 61 20834 939 326 327 295.0 200 Partridge Island, NB Canada 45.239 -66.056 1,085 52 21937 827 244 245 312.0 200 Tampa, FL United States 27.85 -82.543 1,414 203 28094 831 102 103 298.0 100 Upper Keweenaw, MI United States 47.233 -88.628 1,257 316 30161 942 340 341 288.0 200 Cape Ray, NL Canada 47.636 -59.241 1,671 52 33737 778 192 193 292.0 100 Kensington, SC United States 33.491 -79.349 723 198 36717 808 016 017 314.0 200 Card Sound, FL United States 25.442 -80.452 1,619 193 38968 806 012 013 289.0 100 Driver, VA United States 36.963 -76.562 307 173 44091 929 312 313 296.0 200 St Jean Richelieu, QC Canada 45.324 -73.317 693 24 44747 926 318 319 300.0 200 Riviere du Loop, QC Canada 47.762 -69.606 1,073 31 46205 803 006 007 293.0 100 Moriches, NY United States 40.794 -72.756 378 70 46706 799 044 045 290.0 200 Penobscot, ME United States 44.453 -68.776 858 49 46743 771 196 197 294.0 100 New Bern, NC United States 35.181 -77.059 503 181 58907 863 156 157 311.0 200 Rock Island IL United States 42.02 -90.231 1,143 287 59027 838 116 117 319.0 200 Detroit, MI United States 42.306 -83.103 590 301 73240 777 218 219 304.0 200 Mequon, WI United States 43.202 -88.066 1,002 296 73891 792 136 137 297.0 200 Bobo, MS United States 34.125 -90.696 1,367 247 74725 844 094 095 324.0 200 Hudson Falls, NY United States 43.272 -73.542 489 35 74839 870 170 171 309.0 200 Reedy Point, DE United States 39.569 -75.572 121 97 75094 772 198 199 306.0 200 Acushnet, MA United States 41.749 -70.889 561 64 78252 804 008 009 286.0 200 Sandy Hook, NJ United States 40.475 -74.02 266 70 78756 847 058 059 301.0 200 Annapolis, MD United States 39.018 -76.61 82 158
References
- Amalgamated DGPS
- US Coast Guard DGPS Site
- Canadian Coast Guard DGPS Site
- Broadcast Standard for the USCG DGPS Navigation Service - COMDTINST M16577.1
- Transmission Characteristics of Marine Differential GPS (DGPS) Stations
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