Apollo-X User Manual Version 0.9
12
Position Message
Typical position messages are sent in compressed binary format (Type GC) to save on data
usage and are parsed in XeosOnline. If XeosOnline is not used, ASCII GPS (Type AG) can be used
to read position messages as plain text.
Compressed Binary Position (Type GC)
The default format for positions is compressed to save on Iridium data usage. This binary
format is parsed into a readable format by XeosOnline, placing its full contents in the Message
and Location Logs.
The binary format is stackable and can hold more than one position per Iridium transmission. In
this situation, all recorded positions will be displayed in the Location Log in table form, while
the latest position will be displayed in the Message Log.
Timestamp: 2023-06-20T12:00:35.001Z, Voltage Unloaded: 3.54, BatteryV:
2.62, Mode: Normal, Device Temperature (°C): -63, Message Type: GC,
Latitude: 44.714099,
Longitude: -63.604563, SNR: 45, Bearing: 0, Speed: .2880, HDOP: 24.4
Compressed Position
Timestamp
Date and time in UTC of the latest position reading
Voltage Unloaded
Voltage measurement taken before powering the Iridium modem
BatteryV
Loaded voltage of the power supply; minimum battery voltage
observed during the previous Iridium task
Mode
The timer in the scheduler used when the message was
transmitted
Device Temperature
Temperature read before transmission (not used)
Message Type
Displays the message format being transmitted
Latitude
Latitude of fix, decimal degrees
Longitude
Longitude of fix, decimal degrees
SNR
SNR (Signal-to-noise ratio) of GPS Fix, higher is better
Bearing
Direction of movement determined by device to the nearest 22.5°
Speed
Speed measurement in kilometers per hour
HDOP
Horizontal Dilution of Precision
Each compressed message is 23 bytes in size, with an additional 10 bytes added for each
additional “stacked” position.
