Hello,
I have some questions about RM Pro. My uniti is a Lowrance HDS-7 Gen2.

1) Is it possible to use my DGPS (NMEA) to improve survey position?
2) Is there a way to use water sound velocity profiles to correct depth?
3) Any way to use a NMAE Motion Sensor (heave, pitch, and row) to correct data?

Thanks,

Augusto

Hi Augusto,

1. Yes, if your GPS is connected to your unit, then the sonar logs will use this improved data when logging position to file.
2. No. We use depth values that are calculated by the units and logged with the sonar data - we do not calculate the depth ourselves from the sonar returns (although this option is coming).
3. Currently not, but again this is something we are looking at at the moment.

thanks,
Matt

Hi Matt,
Is it already possible to calculate the depth ourselves from the sonar returns with sound velocity?
And is it with the latest update possible to use a NMAE Motion Sensor to correct data?

Thank you,
Sam

I've had a similar request regarding the heading correction by magnetic sensor previously. There is an interesting project going on, that might be relevant here, so I'll just drop a link:
hackaday.io/project/25211-usb-tinytracker

If this device comes to market one day, and its data could be used, I'd think that the SS mosaics would benefit quite a bit.

Matt wrote:
Hi Matt,
Is it already possible to calculate the depth ourselves from the sonar returns with sound velocity?
And is it with the latest update possible to use a NMAE Motion Sensor to correct data?

Kind regards,
Sam

The effect of sound velocity on shallower areas is marginal for single beam echo sounder, why do you need that?
Bigger depth increases the angle and reduces the details you see, I usually lose detail if I go below 10 meters and increase range above 30 meters. A towed sonar can get you close to the bottom on bigger depth to solve that problem.

Are you planning to use a sound speed profiler to get the average sound speed for the water column?

I use a GPS compass to get accurate heading at 10Hz, the gps compass reports true heading with any magnetic deviations. It also reports position at 10Hz with high accuracy.

I supply heading and position to the Lowrance Touch 2 using NMEA0183 and with the latest firmware heading is inserted for every ping and it uses the 10Hz heading data.

RM2 uses heading and gives you great mosaic even in the turns now.

The problems with an external sensor is to sync the data with the sonar pings.
The best solution would be that RM2 logged the pings direct from Ethernet output from the Lowrance unit together with the sensor data from USB. That would also make it possible to get live sidescan data in RM2 :)

Cheers
Hakan

hakan wrote:
Hi Hakan,
I am planning to ploth a depth chart with only a single beam with a beam of 200kHz and a beamangle of 11 degrees up to 60 metres. Because the differences of sound velocity in salt and fresh water influences the measured depth resp. 2 metres, I would like to see I can adapt the velocity in RM.