Hi,

I am using a Lowrance Point-1 antenna, but only as a heading sensor.
GPS Positions are provided by a LGC4000 antenna. (just a matter of placement in the boat)
But now I guess the heading sensor information remains unused in Reefmaster.
Is this true?

Hi Danny,

Headings can be used in the standalone sonar viewer to improve the drawing of sidescan mosaic. You need to ensure that you check the option Use Headings When Available before loading the sonar log file. If headings still don't show with this option checked, please share an example sonar file that shows this behaviour. It could be that your headings are not being logged.

Headings are not currently used in ReefMaster, but will be in the next major version, which will incorporate the new functions in the sonar viewer.

Hi Matt,

I have sent you an example.
Danny Geysen

Hi Danny,
There are no headings recorded in the file that you sent. What is your configuration? Can you see headings on your unit?

The heading sensor makes a big difference. See what happens when you forget to select it ... (see Garmin log on the right - the slip is skew and slightly misplaced in the mosaic. Whereas the Humminbird did have it selected and the slip is dead straight and accurate.

May I ask what the current status is regarding this issue? Is there a new release going to come out soon, or are the Sonar Viewer customers currently the only beneficiaries of heading data?

Yes, it is coming for RM later this year.

That would be nice. I'm usually on a fairly fast flowing river, I guess it would look horrible without heading correction. There are often 20 or more degrees offset between HDG and course.
What would be really nice is to get a function to import a second, more detailed, GPS/heading log, like SonarTRX offers. Then one could just use heading information from a dedicated smartphone, for example. Is such a feature planned?

Yes - synchronising separate GPS/heading logs with sonar logs is planned, and we already have code in development that is working very well. We have been testing with low-cost L1 RTK receivers with very good results, and it does make a very big difference for sidescan mosaics.

The image below shows three tracks - the red one is data recorded on a Lowrance unit, whilst the blue and yellow tracks come from two RTK units mounted fore and aft. Note the deviation in fore/aft tracks when turning corners or running across the strong NE tide on the day. Differencing the two RTK positions also provides accurate headings, and works in the same way as some GPS compasses (bottom image).





In fact we have been getting such good results with these low-cost receivers (post processing raw logged GNSS data) that it should be possible to use them for water level offsetting. In this image you can see the tide rise a metre or so over two hours, plus the journey from car-park -> over embankment -> down ramp to sea:

That's some really amazing stuff! Which L1 receivers did you use? Are these improvements really planned for 2016? That seems like a really big step!

We are using these Reach units from Emlid.They are a very convenient solution, built around an Intel Edison processor with u-blox NEO-M8T GNSS receiver. With built in wifi and blutooth, they can be controlled via a mobile phone and have enough onboard memory to log about 40 hours of raw GNSS data that can be later post-processed to provide a very accurate solution - all that is required in addition to the modules is a 5v battery pack. At the moment we are running two reach units during collection so that headings can be derived, and using local (freely available) CORS data to process for absolute positions. The units also contain a 9 degree of freedom IMU unit ( magnetometer, gyro, accel x 3 each) and ultimately we should be able to get headings, pitch and roll from this.. (waiting for the manufacturers to implement the logging functionality at the moment). This would mean only one unit would be required on the vessel, and the other could be left to run as a base station.
The Reach log is synchronised with the sonar log with a simple brute-force approach to minimise the differences between them, which works surprisingly well and also has the added benefit of providing an accurate absolute start time for each sonar log.

Hello!

I know this thread is very old, but I wanted to follow up and see where ReefMaster is at with the efforts described in Matt's last post in this thread.

I have been using RM2 for some time now and would like to look at improving the overall accuracy of the produced data. I have a number of the Emlid RTK units as well and am very interested in utilizing them to improve heading and position.

Could you provide any updates with the research that was described in the earlier post, and if possible, the workflows involved using the current version of RM2?

Specifically, I'd like to be able to use both the Emlid RS2 position logs and synchronize with the Lowrance SL3 logs, using the timestamp. Secondly, I'd like to use 2 Emilid RS2 units to determine heading. How did you accomplish this in the past? I don't believe Emlid has provided access to the IMU data from the Reach devices, but I could be wrong. Was there any progress on this with Emlid?

My apologies if there is updated information elsewhere in the forum that I missed. I have been looking for clarification on this topic, and this was the most precise thread I could find.

Thanks!