How To read Solmeta GMAX log files
This page is in preparation. If you can help fill in, correct or expand any of the details - especially those marked ?***? which require more explanation, please contact me (Contact button at top!).
The Solmeta GMAX geotagger saves a daily log file in text format. This file is in NMEA (National Marine Electronics Association) format which is essentially text, csv (Comma Separated Values). At first sight this seems fairly impenetrable. This page describes how to read it - some of the entries are repeated, which simplifies things.
Each entry has four lines starting with $. When a photograph is taken an extra line is included which is simply "flash". the four lines start with $GPRMC, $PTNTHPR, $GPGGA and $GPGSA - these identify the type of data that the line contains. A typical entry is
Let us examine these four rows one at a time. Call them rows A, B, C and D. The cells are separated by a comma (,) except for the checksum which is preceded by an asterisk (*) and are identified by numbers in the tables below.
- A1: $GPRMC identifies the line containing the recommended minimum data for gps.
- A2: Time. 24 hour clock (hhmmss.ss) 091444.00 is 09:14 and 44.08 seconds (the Solmeta is a very accurate clock!)
- A3: Navigation receiver warning A = OK, V = warning
- A4: Latitude
- A5: North or South
- A6: Longitude
- A7: East or West
- A8: Speed over ground, Knots
- A9: Course Made Good, True ?***?
- A10: Date. ddmmyy format.
- A11: Magnetic variation
- A12: Magnetic variation East or West.
- A13: D This field was added in NMEA 2.3. The letter may possibly indicate the chipset used. Another site says it is a Mode indicator (N = data not valid,; A = Autonomous mode; D = Differential mode; E = Estimated (dead reckoning) mode. ?***?
- A14: The last two digits are a Checksum (preceded by *).
- B1: $PTNTHPR identifies the line containing the Heading, Pitch and Roll data
- B2: Heading
- B3: magnetic field status ?***?
- L = low alarm,
- M = low warning,
- N = normal,
- O = high warning, or
- P = high alarm.
- C = Tuning analog circuit ?***?
- B4: Pitch
- B5: pitch status as B3.
- B6: roll
- B7: roll status as B3.
- B8: The last two digits are a Checksum (preceded by *).
- C1: $GPGGA identifies the line containing the GPS fix information
- C2: Time. Same as A2.
- C3: Latitude (same as A4)
- C4: North or South (same as A5)
- C5: Longitude (same as A6)
- C6: East or West (same as A7)
- C7: Quality.
- 0 = invalid
- 1 = GPS fix (SPS)
- 2 = DGPS fix
- 3 = PPS fix
- 4 = Real Time Kinematic ?***?
- 5 = Float RTK
- 6 = Estimated (dead reckoning) (2.3 feature)
- 7 = Manual input mode
- 8 = Simulation mode
- C8: Number of satellites being tracked
- C9: Horizontal Dilution of Precision (HDOP) - Relative accuracy of horizontal position.
- C10: Altitude
- C11: Altitude units. M = Meters
- C12: Height of geoid above WGS84 ellipsoid ?***?
- C13: C12 units. M = Meters
- C14: DGPS reference station id
- C15: ?***?
- C16: The last two digits are a Checksum (preceded by *).
- D1: $GPGSA identifies the line containing the Overall Satellite data.
- D2: M=Manual (forced to operate in 2D or 3D), A=Automatic (3D/2D)
- D3: Mode:
- 1 = Fix not available
- 2 = 2D
- 3 = 3D
- D4 - D15: IDs of SVs used in position fix (unused fields are blank)
- D16: PDOP ?***?
- D17: Horizontal Dilution of Precision (HDOP) - Relative accuracy of horizontal position.
- D18: Vertical Dilution of Precision (HDOP) - Relative accuracy of horizontal position.
- D19: The last two digits are a Checksum (preceded by *).
NMEA File Format conversion
There is a free gps data format converter called GPSBabel which will accept NMEA files and will convert them to and from many other formats other formats
Document URI: diy.torrens.org/HowTo/solmetalog.html
Information compiled from various sources including APRS where a lot more information is available.
Page first published: Wednesday the 11th of October, 2017
Last modified: Mon, 19 Aug 2019 21:13:42 BST
© 2017 - 2019 Richard Torrens.