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Drivers Manual

Network - Javad AT4 Event Marker (XA message) - 23

Description

Driver to decode message from a Javad AT4 or from Javad IMU unit and to optionally output event data to an ASCII log file.

These messages may contain attitude (roll, pitch and heading) data, external event markers, position (lat/long/height) data, and/or sensor information data.

Messages from the Javad AT4 that will be decoded are [AR] and/or [XA] records.

These records are defined in the Topcon GPS Receiver Interface Language (GRIL) Manual, version 2.2.
The [AR] records contain roll and pitch (no heave available!) and heading information.
The [XA] records contain the external event markers, specifically decoded by this driver.

In order to decode roll, pitch and heading in addition to the event marker, also define a gyro system using the Javad AT or IMU (Heading) driver, and a motion reference system using the Javad AT4 or IMU (R-P) driver.

Messages from the Javad IMU unit that will be decoded are [ap], [SE], [po], and/or [at] records.

The [ap] records contain roll and pitch (no heave available!), heading, and position information.
The [SE] records contain sensor information (acceleration and angular velocities around the axis), specifically decoded by this driver.
The [po] records contain position information.
The [at] records contain roll and pitch (no heave available!) and heading information.

The driver will automatically detect the different message types.
In order to decode roll, pitch, heading, and position, also define a gyro system using the Javad AT or IMU (Heading) driver, a motion reference system using the Javad AT4 or IMU (R-P) driver, and a position navigation system using the Javad IMU Unit (Position) driver.

Only a Network version (UDP) is available, no serial version.

When the driver is started by starting the QINSy online program, the following window becomes visible:
(Note that initially the window is minimized in the bottom bar and needs to be maximized)

The window shows the decoded event observation number, date and time of the event and the output file (optionally).
Note that, in order to see heading, roll and pitch parameters in the Event Driver dialog box, both a gyro system and MRU system must be defined in addition to this event system.

If a "Javad AT4 Event Marker ([XA] message) (Network)" driver is defined using the same communication parameters as were used in defining the "Javad AT4 or IMU (Heading)" gyro system and the "Javad AT4 or IMU (R-P)" motion reference system,  the observations will be updated only if an [XA] record has been received.
Without defining this event marker driver the heading and motion observations will be updated every time a new record has been received and decoded by the driver.

Each time a new event marker (XA message) is received, the event number displayed will increment by one. The current event number is saved in the Windows registry to ensure that prior events are not overwritten when the QINSy Online program is stopped and then started again.

Driver Information

Driver

Javad AT4 or IMU Unit

Interface Type UDP Driver Class Type Counted 
UTC Driver (question) No Input / Output Input and Output  Executable DrvJavadAT4UI.exe
DrvJavadAT4UDPUI.exe
Related Systems
Related Pages   



Decoding Notes

The solution type & checksum fields are not decoded. The flag field is decoded as the quality indicator. A zero value is decoded as -1 and a value of 1 is decoded as zero.
Sign convention is +ve heading is clockwise, +ve pitch is bow up and +ve roll is starboard side down.

Note

Observations with a negative quality indicator are not used in QINSy. This can be checked with the Observation Physics display.

The driver also decodes the XA-message which contains the following fields:

Format Description

Field

Format

Description

Values, Range, Units

Identifier

Char [2]

Record identifier

Always "XA"

Length

Char [3]

Length coded as ASCII chars

"00A" hex = 10 bytes

ms

Integer

Millisecond part of event time tag

Milliseconds

ns

Integer

Nanosecond part of event time tag

Nanoseconds

Scale

Char

Time scale

0 = GPS
1 = UTC_USNO
2 = GLONASS
3 = UTC_SU
4...254 = Reserved

CS

Char

Checksum

A generic observation is filled with value 0.0 and the observation time is set to the value decoded from the data.
The quality indicator is set to the decoded scale.

Database Setup

To decode the heading, add a "System" of type "Gyro", select the driver, and define the heading 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 driver name and the same I/O parameters for both systems.

The unit for roll, pitch and heading must be set to Degrees

To decode the event marker, add a "System" of type "Miscellaneous", select the driver "Javad AT4 Event Marker ([XA] message) (Network)".
Add a new generic observation and give it a correct name.
The event marker observation will start at a value of zero and will be incremented by one every time an event marker record is received.

If the roll, pitch or heading are also decoded, make sure that the same I/O parameters are selected for both systems.

Online

If a "Javad AT4 Event Marker ([XA] message) (Network)" driver is defined using the same communication parameters as the position driver an output file will be created in case the user decides to record data to a raw database.
In case the user pauses the recording the output to this file is also paused.
File splitting as used for raw databases is not supported. The file uses the same naming convention as the raw database and is stored in the "LogFiles" subfolder of the project folder.
It contains the last value of the each of the observation which were received just before the occurrence of the event marker.

Format Example
Date,Time,Event,Latitude,Longitude,Height,Heading,Roll,Pitch

15-3-2005,09:27:32.000,13,,,,295.4626,1.1411,1.5350
15-3-2005,09:27:33.000,14,,,,295.4584,1.1185,1.3720
15-3-2005,09:27:34.000,15,,,,295.5360,1.4105,1.7046
15-3-2005,09:27:42.000,23,,,,295.5265,1.1414,1.4622
15-3-2005,09:27:43.000,24,,,,295.2147,0.6477,1.7100
15-3-2005,09:27:44.000,25,,,,295.1323,0.2946,1.6318

In this case the user paused between event 15 & 16 and resumed recording between event 22 & 23.