I have two DST810's and have had issues with one of them since install. If you search on various forums or just the internet in general, you'll find people having similar issues for a number of years. I'm involved in a forum thread on TrawlerForum about flaky depth and speed readings, etc. that you can probably find. Mine show up as DST200s in NMEA 2000-land as well, which is irritating.

However, it doesn't necessarily mean that your sensor is dead or broken just because it is showing weird depth. It could be thermoclines in the water, reflective junk, or a number of other reasons. Mine routinely will show 6 feet depth for 5-10 minutes and then go back to showing actual depth, and it is clean (I've removed it many times) and there are no other issues that I know of configuration or location wise. 

There are some spots where I've found this to happen reliably, over and over, and I assume it has to do with the water or the bottom, and that the sensor just can't read it. Those spots I know I will lose accurate depth. But it also happens randomly in places which is the irritating part.

I've also looked at alternatives, and there aren't any. Airmar is really the only game in town, and the ultrasonic stuff seems like it has its own set of problems. I'd be curious if you are able to correlate specific areas that have issues, or if it is something that just goes haywire, like mine, in random spots as well.

Posted by: @stevemitchell

I have two DST810's and have had issues with one of them since install. If you search on various forums or just the internet in general, you'll find people having similar issues for a number of years. I'm involved in a forum thread on TrawlerForum about flaky depth and speed readings, etc. that you can probably find. Mine show up as DST200s in NMEA 2000-land as well, which is irritating.

However, it doesn't necessarily mean that your sensor is dead or broken just because it is showing weird depth. It could be thermoclines in the water, reflective junk, or a number of other reasons. Mine routinely will show 6 feet depth for 5-10 minutes and then go back to showing actual depth, and it is clean (I've removed it many times) and there are no other issues that I know of configuration or location wise. 

There are some spots where I've found this to happen reliably, over and over, and I assume it has to do with the water or the bottom, and that the sensor just can't read it. Those spots I know I will lose accurate depth. But it also happens randomly in places which is the irritating part.

I've also looked at alternatives, and there aren't any. Airmar is really the only game in town, and the ultrasonic stuff seems like it has its own set of problems. I'd be curious if you are able to correlate specific areas that have issues, or if it is something that just goes haywire, like mine, in random spots as well.

Hey @stevemitchell,

Testing so far has been limited. It seemed to behave on the trip from Shilshole back to our slip @ EBM. Now sitting in the slip it will follow the tidal changes for a bit and then revert back to 15'. I strongly doubt it has anything do with the seabed floor underneath our slip as it just goes back to 15' no matter what the tide height. I was hoping the DST810 would be more reliable than the 800, i guess not. This is what it looks like in grafana. I'm going to graph the temperature readout and see if i see a similar change at the same time. 

 https://imgur.com/a/nhrv5u6 

Yikes that is a lot more than mine does. Is this brand new? Did you make sure they didn't paint it with your recent bottom job? Mine had some paint on it from my yard time in August, but that didn't seem to make a difference once I cleaned it.

Oh and just to be clear, I have the 810 and 800 - one of each. That was a typo....

@stevemitchell

Yup brand new. It appeared to be clean when i looked at it while it was still on the hard. I didn't check it just before we splashed. I guess I could pull it up and take a look. Just checked the temp graph and that seems to be working fine. 

This thread grabbed my attention as I'm planning to buy a DST810 in the near future. But, I think Steve is right - its probably related to thermoclines. Maybe the 810's internal software is not quite as good at filtering out thermoclines as others? That said, I do a fair amount of marine geology research, and the thermoclines in the ocean are impressive - particularly at shallow depths. We commonly do CTD casts (conductivity, temperature, depth profiles) to get better water column velocity data to make better maps of the ocean bottom. Attached is a CTD cast (randomly grabbed off the web) showing how temperature and salinity varies near the sea surface. Such layers give rise to reflections and can fool the depth sounder. 

@peterh

Interesting information. I will see if it does it while we are underway. I also just installed a BBDS1 with an airmar 744v transducer and it works flawlessly.