iXBlue Octans MRU (HEHDT) (Heave Up O) - 05

Description

Please use preferred Driver:
IxSea Octans TAH ($PHOCT) driver
* Octans
* Hydrins
* Landins
* Phins (optional)
* Rovins

Driver for iXSea (previously Photonetics) Octans solid state MRU.
Driver can decode NMEA messages $PHTRH or $PHTRO/$PHLIN and/or $PHSPD and/or $HEHDT and $PHINF.
Driver is used to decode roll-pitch-heave observations, local speeds and/or heading.

The Octans unit should be programmed to output in GYROCOMPASS 2 mode or OCTANS STD1 mode. 
The GYROCOMPASS 2 mode is preferred because it outputs heave, pitch and roll in a single string.

In GYRO COMPASS 2 mode the Octans will output data using this specific sequence: $HEHDT, $PHTRH, $PHSPD, $PHINF.
The latter is a status message that is used to update the quality indicators of the heading/pitch/roll/heave observations.

In OCTANS STD1 mode the Octans will output data using this specific sequence: $HEHDT, $PHTRO, $PHLIN $PHSPD, $PHCMP, $PHINF.
The $PHCMP is a status message which is not used, the $PHINF message is used to update the quality indicators of the heading/pitch/roll/heave observations.

Two versions of the driver are available: a Serial version and a Network version (UDP).
The internal workings of the drivers are the same except for the data reception.
Please be aware of the following when using the network version: None of the messages contain a time/date field, so timestamping of the data is done when received at the UDP Port.
Due to network characteristics, unpredictable latencies can be introduced, which may result in very inaccurate timestamping of the data. It is not recommended to use a network version in combination with e.g. a multibeam survey.

Driver Information

Decoding Notes

The timetag of the arrival of the HEHDT message is used for the pitch/roll/heave observation.

The status bits Bit3-Bit0 from the $PHINF message are used to determine the quality indicators of the Pitch/Roll/Heave/Heading.
If respective Status bit is 0 then the quality indicator is set to 1.
If Status bit is 1 (error) then the quality indicator is set to -1.

Note that for the computation, observations with quality indicator equal to -1 are rejected!

Database Setup

To decode also the pitch, roll and heave, add a "System" of type "Pitch, Roll and Heave Sensor". Select the driver and define the driver parameters.
To decode all four observations (pitch, roll, heave and heading), add both these system types to the Qinsy database and make sure to select the same gyro driver as the MRU driver (regarding the heave convention) and the same I/O parameters for both systems. 

Drivers IO Notes

Command line parameter "U" will decode a 'U' heave sign as heave up, whereas parameter "O" will decode an 'O' heave sign as heave up.
"NOCS" will not decode and test the checksum field in the messages.

Additional Information

Firmware version

The Photonetic manuals used to describe that 'U' is plus for heave up, but when older Octans systems were lifted, the heave sign character used to be 'O'.
In recent firmware versions, this problem has been solved, so iXSea Octans systems will output a 'U' when the Octans is lifted, which corresponds to the manuals.

QPS is not sure in which firmware version this problem has been solved, but Photonetics has confirmed us that Octans firmware 4.6, or higher, should be according to the Heave Up 'U' conventions.
Use the I/O Test Utitlity in Qinsy to check which is the output character when the Octans is lifted, 'U' or 'O'.