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Report on internally mounted GPS sensor


(Kevin) #1

Bottom line up front: GPS works on ArduSub and BlueROV2, but it needs to be mounted on a mast and out of the water to work properly.

After getting a proper tablet earlier in the week, I set about doing various ROV tests. One of these was to finally get the system wet.

The results are below.

Screenshot 8 shows the ROV out of the water with a good GPS lock.

Screenshot 9 shows the ROV in the water, disarmed and on the surface. You can see how it looses lock and the GPS wanders according to inputs from the IMU.

So what next? Well, we are either going to need to make a mast and mount an antenna externally or reconfigure an antenna inside the hull. There isn’t a lot of room to do the latter, so I am open to ideas.




(Jacob) #2

I wasn’t expecting anything else, but good to hear that you have physically confirmed this.

I am curious on how you determined/tested this. Can you elaborate on that?

-Jacob


(Kevin) #3

Jacob,

Here’s how I had the GPS sensor mounted. There isn’t enough room to mount it horizontally or else I would have.



(Jacob) #4

Oh, I see now with the screenshots how you see that the gps is working/not working. I test with a usb gps on a mast. Do you have a raspberry pi on your ROV? I can explain how to get the gps into ardusub if that is the case.

-Jacob


(Kevin) #5

Sorry about that, hit “enter” before I was done with the post.

Yes, I have the Raspberry Pi variant, let me know how you went about setting up the USB GPS option and I’ll start looking at alternatives.


(Jacob) #6

Ok, first of all, you will be limited to about 3ft depth, or whatever your mast is, but I wouldn’t recommend a longer mast than that (make sure your mast is stiff!). I use a BU353-S4 gps, and scripts designed specifically for that unit. The first step will cutting the usb cable so that you can penetrate it, then reconnecting the usb once penetrated. The usb gps plugs into the raspberry pi. I will provide some more details at a later date. I will update the ArduSub documentation in the meantime so everyone can benefit.

 

-Jacob


(Kevin) #7

Thanks, I’m familiar with the BU353-S4. I’ll order a few and get one integrated with a penetrator. any idea if the GPS is sealed, or does it need to be encased in epoxy?

I’m thinking of making a 3D printed mount and using some of the existing mount holes. Be a nice little addition.


(Ryan) #8

I can confirm the same gps behavior. It seems like anything more than a foot underwater and I lose gps. It’s still handy to have once you are surfaced.

I mine is a custom frame but similar layout to BROV2.

Excuse the cat and mess on the work bench :slight_smile:




(Kevin) #9

Awesome rig there Ryan! Can’t wait to see it get wet.

I like where you mounted your GPS. How many satellites do you get or what does your GPS lock look like when it is on the surface?

I could probably try rotating my BR2 electronics chassis and remounting the camera, but things might get a little weird.


(Rusty) #10

@Ryan - Very cool frame! I like the design.


(Ryan) #11

Thanks guys. I tried to design it to be as compact as possible using some left over materials. I’m still not 100% satisfied with it and would like to add clamps for the center tubes.

It has been in the water. The first test was in a quarry here in KY. It made it to 40ft with no issues! Credit goes to everyone that has been developing ardusub.

 




(Paul) #12

Good test Kevin, although the results were pretty much what a lot of us thought would happen. FYI, the VideoRay CoPilot system uses an active GPS antenna potted in a shark-fin / surfboard fin apendage on top of the float block. I rather like that idea over a wand, less likely to snag.



(Kevin) #13

The Riptide UUV has a similar setup with the GPS mounted in a fin. The fin works fine for vehicles that go straight, but we have strafing capabilities. I’m thinking of more of a “support” that is mounted in a few of those holes on the top of the frame. So not a wand-like mast, but maybe something angled that gets the sensor up about 2 inches out of the water.


(undersearobotics.com) #14

Any updates? I’m thinking about adding a GPS (maybe this one) in the main housing.


(Kevin) #15

No updates as of right now. That was the GPS module I was going to try and install too.


(Svein H.) #16

I have installed this one, but it will loose signal as soon as i come below the surface…


(Mark Langille) #17

We are going to look at adding on as well. Is the stock software setup to handle the GPS already or is there any special config needed?

We have a number of Pixhawk GPS kicking around from UAVs so figured may as well use one to provide surface positioning before a dive.


(Svein H.) #18

Just plug in and you get the potition in the map. You can also have the potition displayed in the overlay field


(undersearobotics.com) #19

Yes, that is to be expected. But did it work well while the ROV was on the surface? I plan on building a waterproof “pod” and “mast” to hold the GPS above the water’s surface.


(Svein H.) #20

Yes it did. The reason for installing it was just to be able to take fixes at surface before diving.