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BR2 alternative GPS solution


(Othonas) #1

Hi guys,

I have acquired my BR2 a few months ago and I 'm thrilled ever since!!! I’m planning on using it mostly for photogrammetry and would like to find a relatively easy solution to have GPS positioning on specific target points. I am aware of the Water Linked kit and I will definitely add it on as soon as I have the budget so I am looking for an alternative until then. Any suggestion is more than welcome.


(Bo Koppel) #2

Hi!
There are some lowbudget workarounds, but not near Waterlinkeds possibilities.

If You can live with topside position only, you can send GPS NMEA stream to companion in ROV.
That way you get positioning in QGC status window also, so screenshots will have “positioning”

Another way people have used is a buoy dragged above the ROV with a wifi GPS built in.
Then You can receive wifi positioning of buoy and send that NMEA strings further.
People have also used a basic standalone GPS tracker on a buoy, then you have timestamped positioning to match your photage at office.


(Othonas) #3

Thanks Bo!

One solution we have in mind as well is the buoy. Another way is to use a scuba diver as there will be one positioning some necessary control points (at least at areas with depths up until 30-35 meters)

If You can live with topside position only, you can send GPS NMEA stream to companion in ROV.
That way you get positioning in QGC status window also, so screenshots will have “positioning”

Can you give me some more info about this? How it works and what readings i will get back?


(Marcus) #4

The NMEA streaming works by porting a GPS string to the companion computer, which gives the Pixhawk a GPS lock, and is then reported in QGroundControl. When it is working, you can activate lat/long in the QGC gauge and position will show up. The way we do it with a surface GPS:

  • download NMEA Router. The original host page seems to be gone, but you can get it here

  • plug in your GPS device to topside computer. We use small USB GPS pucks.

  • open NMEA Router and make two new connections

  • connection 1 is configured as “input” serial device on the com port your USB GPS is on. Once it is enabled you should start to see NMEA sentences coming through NMEA Router

  • connection 2 is configured as “output” UDP, IP 192.168.2.2, port 27000

  • you then need to make a new “route” which pairs these two connections

  • save your profile for next time (though you may need to edit the topside connection each time since the USB port allocation may change)

  • make sure both connections and route are enabled

  • you know it is working when the Pixhawk light changes from flashing blue to flashing green

Once that is all done, you will have position on your gauges, and the map inset will show your position marked with a BR2!!


#5

Having a little more background from your other photogrammetry topic, if I understand you and what you’re trying to do with target or control points correctly, then you might not need any ROV GPS-awareness at all.

If the intent is only to produce position-referenced photogrammetry products, you (human) can visit the location above each control point and take surface coordinates there. Depth can be plumbed or measured by flying the ROV. If you’re placing control points manually, then I’d assume you’d already have them on a line and would be visiting each spot already.

Using Agisoft Photoscan as you mentioned in the other thread, you only need a few control points to geo-reference the whole thing. (A location where each picture is taken via the Water Linked system would be nice, but the geo-referencing results in Photoscan would likely only be marginally better.)


(Jacob) #6

In the situation you describe, you are telling the ROV that it’s GPS coordinates are the coordinates of the boat. This isn’t ideal, as the boat’s movements will not correlate to the other sensor data on the ROV, and can upset the filters running in the autopilot software.

All that you need to do is connect the USB gps to your computer, and select the NMEA GPS COM port and baudrate in QGC. Then the boat position will be shown in QGC.


(Marcus) #7

Thanks @jwalser but I’ve never been able to get GPS position that way. Whenever I try, position isn’t shown, and QGC crashes. It then crashes multiple times when restarting until eventually opening properly, but still no position, and will crash eventually unless I disable the GPS com port selection. Using Windows 10 with up to date QGC and companion software.


(Othonas) #8

Thank you all for your help!!! @spotxuv and @jwalser if I understand this correctly the reading I will get will be based on my computer’s position. However I will have a better look on this just to see how it works. @skcolb you do have a point here! If I use a boat or a scuba diver (or both) it will be relatively easy to have my readings. What I am trying to see is if there is a solution where I can do the same using only the Rov and nothing else