User manual GARMIN DGPS 53

[. . . ] DGPS 53 integrated GPS/DGPS receiver owner's manual and reference guide © 2000 GARMIN Corporation GARMIN International, Inc. 1200 East 151st Street, Olathe, Kansas 66062, U. S. A. 913/397. 8200 or 800/800. 1020 Fax 913/397. 8282 GARMIN (Europe) Ltd. Unit 5, The Quadrangle, Abbey Park Industrial Estate, Romsey, SO51 9AQ, U. K. [. . . ] <10> Root of semi major axis <11> Omega, argument of perigee <12> Longitude of ascension node <13> Mean anomaly <14> af0 clock parameter <15> af1 clock parameter 11 Operation Using the DGPS 53 Sensor Initialization Information (PGRMI) The $PGRMI sentence provides information used to initialize the position and time used for satellite acquisition. Receipt of this sentence by the DGPS 53 causes the software to restart the satellite acquisition process. If there are no errors in the sentence, it will be echoed upon receipt. If an error is detected, the echoed PGRMI sentence will contain the current default values. Current PGRMI defaults can also be obtained by sending "$PGRMIE" to the board. $PGRMI, <1>, <2>, <3>, <4>, <5>, <6>, <7>*hh<CR><LF> <1> Latitude, ddmm. mmm format (leading zeros must be transmitted) <2> Latitude hemisphere, N or S <3> Longitude, dddmm. mmm format (leading zeros must be transmitted) <4> Longitude hemisphere, E or W <5> Current UTC date, ddmmyy format <6> Current UTC time, hhmmss format <7> Receiver Command, A = Auto Locate, R = Unit Reset Sensor Configuration Information (PGRMC) The $PGRMC sentence provides information used to configure the DGPS53. Configuration parameters are stored in non-volatile memory and retained between power cycles. The DGPS 53 will echo this sentence upon its receipt if no errors are detected. If an error is detected, the echoed PGRMC sentence will contain the current default values. Current default values can also be obtained by sending "$PGRMCE" to the board. $PGRMC, <1>, <2>, <3>, <4>, <5>, <6>, <7>, <8>, <9>, <10>, <11>, <12>, <13>, <14>*hh<CR><LF> <1> Fix mode, A = automatic, 2 = 2D exclusively (host must supply altitude), 3 = 3D exclusively <2> Altitude above/below mean sea level, -1500. 0 to 18000. 0 meters <3> Earth datum index. If the user datum index (96) is specified, fields <4> through <8> must contain valid values. Otherwise, fields <4> through <8> must be null. Refer to Appendix A for a list of earth datums and the corresponding earth datum index. <4> User earth datum semi-major axis, 6360000. 0 to 6380000. 0 meters (. 001 meters resolution) <5> User earth datum inverse flattening factor, 285. 0 to 310. 0 (10-9 resolution) <6> User earth datum delta x earth centered coordinate, -5000. 0 to 5000. 0 meters (1 meter res. ) <7> User earth datum delta y earth centered coordinate, -5000. 0 to 5000. 0 meters (1 meter res. ) <8> User earth datum delta z earth centered coordinate, -5000. 0 to 5000. 0 meters (1 meter res. ) <9> Differential mode, A = automatic (output DGPS data when available, non-DGPS otherwise), D = differential exclusively (output only differential fixes) <10> NMEA Baud rate, 1 = 1200, 2 = 2400, 3 = 4800, 4 = 9600, 5 = 19200, 6 = 300, 7 =600 <11> Velocity filter, 0=No filter, 1=Automatic filter, 2-255=Filter time constant (10 = 10 second filter) <12> PPS mode, 1 = No PPS, 2 = 1 Hz <13> PPS pulse length, 0-48 = (n+1)*20msec. Example n = 4 -> 100 msec pulse <14> Dead reckoning valid time 1-30 (sec) 12 Operation All configuration changes take effect after receipt of a valid value except baud rate and PPS mode. Baud rate and PPS mode changes take effect on the next power cycle. Using the DGPS 53 Output Sentence Enable/Disable (PGRMO) The $PGRMO sentence provides the ability to enable and disable specific output sentences. The following sentences are enabled at the factory: GPGGA, GPGSA, GPGSV, GPRMC, and PGRMT. $PGRMO, <1>, <2>*hh<CR><LF> <1> Target sentence description (e. g. , PGRMT, GPGSV, etc. ) <2> Target sentence mode, where: 0 = disable specified sentence 1 = enable specified sentence 2 = disable all output sentences 3 = enable all output sentences (except GPALM) The following notes apply to the PGRMO input sentence: 1) If the target sentence mode is `2' (disable all) or `3' (enable all), the target sentence description is not checked for validity. In this case, an empty field is allowed (e. g. , $PGRMO, , 3), or the mode field may contain from 1 to 5 characters. 2) If the target sentence mode is `0' (disable) or `1' (enable), the target sentence description field must be an identifier for one of the sentences being output by the DGPS 53. 3) If either the target sentence mode field or the target sentence description field is not valid, the PGRMO sentence will have no effect. [. . . ] And, certainly, if there aren't enough satellites to determine a GPS position, there aren't enough satellites to calculate a DGPS position. Atmospheric Conditions-- Differences in the ionosphere and/or troposphere between the DGPS broadcast station and the DGPS receiver can result in decreased position accuracy. Although this does not cause significant error, the amount of error can increase as you get further away from the DGPS broadcast station. Satellite Geometry-- A minimum of 4 satellites are required to determine a 3D position. [. . . ]