Home        Store        Docs        Blog

Airmar DX900+ for ROV?


(Tim) #1

http://www.airmar.com/uploads/brochures/dx900-multilog-sensor.pdf

Looks like this may finally be on the market for about $1k… Water speed vector sensing plus depth and temperature. Understanding that it measures relative water speed and not true water speed, could this be useful on an ROV?


(Kevin) #2

Hi Tim, (I’d recommend you assign a category to this thread so it doesn’t fall off the “Latest Posts”)

I’ve been looking at the DX900 as well, but as a future replacement for our DST800 on our support vessel.

This probably won’t be comparable to a DVL for positioning. I’d recommend the WaterLinked system for positioning. Speed through water for a tethered ROV? I’d say it would be a “nice to have”. The depth (altitude in this case) would be useful, but I’ve heard rumors there is something in the works. Now, if we start talking untethered autonomous, that’s where things get interesting.

I also know the @nidorobotics guys were working with the 800 series awhile back for a client so they might be able to shed some light on this.


(Tim) #3

Thanks Kevin, I just put it in General Discussion. Noob oversight, my first original topic here.

The DX900 seems like it has potential as a mid-budget navigation tool for those who can’t afford a DVL or USBL. I imagine integration for navigation could be tricky and it would probably only be semi-accurate but the technology and price make this unit interesting, especially if one is already planning on adding a sonar for altitude.

I see this idea has been covered briefly already: Using current meters to localize a rov

I do have a DT800 that I will try to implement on my ROV once it’s finished, wish a DX900 was in the budget just to experiment with…


(Kevin) #4

I agree, it’s a starting point, but I’m not quite sure it will get us there. I’m not quite sure a small vehicle will be moving fast enough to get accurate speed through water measurements. I still think some sort of “bottom lock” is required to really determine velocity.

Now if the depth transducer that comes with the DX900 factors into the velocity calculations, that would really be something. Maybe the next version? I need to do more research into what a Nautical Leeway Angle is as I’ve never hear it before.

A good experiment nonetheless.


(Enrique) #5

Hi Tim,

We have used a DST800 only for data collection, not for navigation. The water speed measurements are not enough for relative positioning, but I have been wondering if inercial data could have enough accuracy for this purpose, maybe someone has experience in this?

Also, the DX900 has a 60m depth rating, that would be a limitation for the BlueROV2.

Maybe it is more interesting to see if those rumors bring something smaller and more suitable for small ROVs :wink:


(Tim) #6

The DX900 has +/- 0.1 kt speed accuracy, perhaps good enough? I hope the ‘something in the works’ materializes…


(Kevin) #7

On closer look at the data outputs, I’d say “no” for the NMEA 0183 Speed sentences, but there is a PGN in the NMEA 2000 category that looks interesting, the “130578 Vessel Speed Components.” I’m trying to see how the sentences are broken out on that one. And obviously, we don’t have a NMEA 2000 reader yet.