Olex can be connected to various trawl and ROV positioning systems. The trawl is visualized on the Olex screen in 2D and 3D with distance, direction, and door spread. It is also possible to track each trawl door in addition to own vessel.
ROV positioning with NMEA $PSIMSSB
The NMEA sentence $PSIMSSB comes in different varieties. Those understood by Olex, contains a bearing from the boat to the ROV. Others will give format errors. The equipment that generates the message must know the boat's true heading.
The sentence should contain at least 10 fields separated by commas, the first one being a time stamp. The second is a name of the ROV target, and the third should be "A". The fourth field is empty, and the fifth should be "C". The sixth should be either "N", "E" or "H", and the seventh can be any character. Fields number 8 and 9 is the horizontal distance in meters from boat to ROV, and number 10 is the vertical distance.
Should the sixt field be "H", the sentence $PSIMSNS must be received on same port as $PSIMSSB, to convey the heading of the boat.
Below is an example of $PSIMSSB which would not work, but instead give format error:
The error is that field 5 is "U" which means the the sentence provides an absolute position in UTM instead of a relative bearing.