Seacraft ENC3 Inertial navigation unit?

[Tassi Devil Diver]

Have been looking into this too, from my understanding the propeller is an optional extra and is not needed to track movement only to display speed.

 

[stuartv]

Have been looking into this too, from my understanding the propeller is an optional extra and is not needed to track movement only to display speed.

Good info. I was wondering why they would need that propeller. If the 3D accelerometer(s) is accurate and precise enough, it shouldn't need a prop to track movement and position. Using the prop just to display water speed makes sense. I would expect that it can show ground speed without the propeller.

 

[napDiver]

Per my understanding of using accelerometer data...

You can "guestimate" position/direction/path with accelerometer but it won't be very accurate. Otherwise, we wouldn't need GPS at all for location tracking. It would be helpful for heading and direction for long segments.

 

[stuartv]

Per my understanding of using accelerometer data...

You can "guestimate" position/direction/path with accelerometer but it won't be very accurate. Otherwise, we wouldn't need GPS at all for location tracking. It would be helpful for heading and direction for long segments.

I think your statement is inaccurate by virtue of being incomplete. I think it might be correct to say "you can guesstimate position/direction/path with accelerometer but it won't be very accurate using affordable consumer grade accelerometers that were available in 2017."

Or something like that. I mean, I think submarines having been using accelerometers to do very accurate tracking for years. They just use big, really expensive components. Those components have not been available in a small enough size, while also being affordable, to use on consumer DPVs (for example). Maybe until now...?

Maybe the tech has finally advanced enough that we CAN do position/direction/path tracking with modern accelerometers. Ones that are small and inexpensive. And accurate ENOUGH. I mean, it's not like we're going to use one of these ENC3 units to navigate over 1000 miles of sea bottom.

Personally, if I can get in the water, scooter around for a couple of miles, and get back to within 30 - 50 feet of my starting point, that is plenty accurate enough for me.

 

[stuartv]

Well, @napDiver, I think you were right about the current state of accelerometer data.

I wrote Seacraft and asked questions. This is the response I got (bold added by me):

The ENC3 uses a mix of GPS and inertial guidance. It records the last known GPS position on the surface and from there, gyro, compass and pressure sensor take over to extrapolate the position.

To do this, the ENC3 needs a speed sensor, tracking the speed of the forward motion in the given compass direction.

When the movement stops, the ENC can be programmed to automatically stop recording and to continue when there is a movement again.


So far, so good.

Since the civil version oft he ENC has no means to get GPS signals under water, there is of course an error margin, especially when it comes to currents, drift and rapid changes in salinity or in the surrounding magnetic field.


The latter can be observed live on the ENC display, showing indications oft he surrounding magnetic field and of magnetic objects nearby.

Currently, there is no drift or current compensation, as the calculations and sensor arrays to achieve that are rather complex.


So, you currently have no guarantee to find your way with ENC properly, when there is a drift or current or flow involved.


All other functionalities like using GPS under water, setting waypoints etc. are currently limited tot he military versions oft he console.

 

[stuartv]

I had a feeling it was too good to be true.

 

[-JD-]

Well, I find this last sentence to be rather interesting:

All other functionalities like using GPS under water, setting waypoints etc. are currently limited tot he military versions oft he console.

GPS under water. Are they trailing a floating receiver or is there some sort of amazing techno-magic that has been developed?

 

[stuartv]

Well, I find this last sentence to be rather interesting:



GPS under water. Are they trailing a floating receiver or is there some sort of amazing techno-magic that has been developed?

No idea on that.

 

[-JD-]

No idea on that.

They'd probably have to kill you if you did.

 

[AJ]

According to the specs it has a 3D gyroscope. Does this mean the compass is'nt magnetic? I'am struggling to find a decent spot for my magnetic compass on my scooter.

Included sensors:
3D magnetometer, 3D gyroscope, 3D accelerometer, pressure sensor, temperature sensor