P4 RTK for Ag Mapping

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Hi All,

I've been searching heavily on how to use my new P4 RTK specifically for my application. Unfortunately my DRTK 2 base station failed out of the box (won't switch on at all), and has gone back for warranty, hopefully a new replacement.

I'm not new to DJI drones, but I am to all this mapping thing. I have only one need, to map my own very flat paddocks so I can set them up in Terra Ag and spray them with my Agras spray drone. I don't need sub cm accuracy, I'd be vary happy with 30cm and delighted with 10cm. Again, I'm not going for survey grade results but I do want my 30k drone to respect the boundaries and obstacles I enter into Terra Ag within reason.

1. Do I need ground control points for the accuracy I need? I certainly don't want to do them, as I thought the whole point of RTK was so you didn't need them. Again, 10-30cm accuracy would be fantastic for me.

2. Do I need reference points, and what are they compared to GCP's? Do they have to be at ground level, or could they be the tops of posts, etc which would be very much easier.

3. I would really like to leave whatever field spraying job I design on file, and be able to use it again in the future without mapping/planning it all again. Is that possible? Will it be reliable in the future, or should I do it all again each time? I'm thinking if it goes well, that would be the one to use next time, kind of like a 3D print file.

4. Standard or SDK controller? I've got both, and an Android tablet for the SDK, but I'd like to start simple and I certainly don't want to pay for a 3rd party app at this stage. My Agras spraying mentor is mapping with an M300 and UCGL, pretty sure in 3D as well, but he's very experienced and spraying extremely hilly country full of trees. My place is wide open flood plains, very flat with the odd tree here and there. I'm thinking of starting with 2D maps and the basic controller until I get settled, unless there's a compelling reason not to. I'd only do contract work for immediate neighbors on the same sort of land.

5. Mapping height etc? I see it's set at 100m and 50m is the minimum. At 60m I'm clear of any tree on the property by 20m's. Would that be a good height for my application? It's pretty windy where I am, and my MPP certainly likes it lower in that regard.

6. Will I just leave the camera and mapping settings on auto/standard? I would imagine they'd just set them to work as they designed the thing?

When answering these questions above, please consider my application which is spraying 6m wide swathes at about 2.5m above the field. I don't need survey grade accuracy, anything less than 30cm (1 foot) will be ideal. Being able to store spray jobs on the computer would be excellent as long as they were repeatable. To much fiddling around will scare off customers, they want you to do the job and leave.

I would appreciate any advice or tips, thank you
 
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Hi Cap,

Did you make any progress on this? I'd be very interested to have a chat about your processes & requirements with the spray drones.

We're just about ready to launch our weed mapping & management platform (agristry.com), which is hopefully exactly what you're looking for (shameless plug).

We've got the entire process automated, just upload the images & select your buffer size. All the image stitching & weed mapping process is run automatically in the background and returns a shapefile which allows for variable rate application according to weed sizes (and nozzle limitations).

We've been working mostly with large broadacre farmers and integrating these weed maps directly into their boom sprays to achieve spot spray results at scale without the limitations and costs involved with camera sprayers.

If anyone would like to test out the platform, just sign up. It will continue to run for free until we have published our case studies.
Feel free to sign up, I'd love to get feedback. https://my.agristry.com is the link to try it out.


Question time:

1. RE GCPs: Because your terrain is flat, you should be able to get within 0.5m (X & Y) accuracy without using control points. It'll be height accuracy that is the most effected the most. As long as your terrain is flat, this will not have a huge effect on your X & Y accuracy. The less flat the terrain, the more impact vertical accuracy will have on X & Y.
*If you upload to Agristry, shoot me a message and I'll send you the accuracy report


2. Reference points are similar to GCP's. Many GCP's are used to assist during the stitching process VS reference points which are used to assess the accuracy of the stitching job.
For your requirements, fence posts make great GCP's. The trick is that you'd first need your DRTK pole to measure the exact location of the top of the post

3. This is why the strainers (corner fence posts) make for such great GCP's. Once you've measured & painted them you can re-use them without being that guy pinning out a heap of GCP's through a field.

4. I've got both, it's personal preference. For large agriculture mapping jobs I much prefer the SDK controller with a good tablet. Because: less likely to drop the controller using a tablet & if you do, it is much less likely to break anything.

5. This is project specific. The P4RTK can handle wind VERY well but you have to increase the overlap a bit on windy days.
*For weed detection we mostly fly at 120m for 3cm/px but again, it depends on the job.

6. I recommend leaving camera settings at standard, it makes workflow simple.
When creating our weed detection platform, we ONLY used standard camera settings when training our algorithm. This is becacuse we can't expect end users to have knowledge of photography.

Reach out if you have any questions.

Regards,
Darren
 
Hi Cap,

Did you make any progress on this? I'd be very interested to have a chat about your processes & requirements with the spray drones.

We're just about ready to launch our weed mapping & management platform (agristry.com), which is hopefully exactly what you're looking for (shameless plug).

We've got the entire process automated, just upload the images & select your buffer size. All the image stitching & weed mapping process is run automatically in the background and returns a shapefile which allows for variable rate application according to weed sizes (and nozzle limitations).

We've been working mostly with large broadacre farmers and integrating these weed maps directly into their boom sprays to achieve spot spray results at scale without the limitations and costs involved with camera sprayers.

If anyone would like to test out the platform, just sign up. It will continue to run for free until we have published our case studies.
Feel free to sign up, I'd love to get feedback. https://my.agristry.com is the link to try it out.


Question time:

1. RE GCPs: Because your terrain is flat, you should be able to get within 0.5m (X & Y) accuracy without using control points. It'll be height accuracy that is the most effected the most. As long as your terrain is flat, this will not have a huge effect on your X & Y accuracy. The less flat the terrain, the more impact vertical accuracy will have on X & Y.
*If you upload to Agristry, shoot me a message and I'll send you the accuracy report


2. Reference points are similar to GCP's. Many GCP's are used to assist during the stitching process VS reference points which are used to assess the accuracy of the stitching job.
For your requirements, fence posts make great GCP's. The trick is that you'd first need your DRTK pole to measure the exact location of the top of the post

3. This is why the strainers (corner fence posts) make for such great GCP's. Once you've measured & painted them you can re-use them without being that guy pinning out a heap of GCP's through a field.

4. I've got both, it's personal preference. For large agriculture mapping jobs I much prefer the SDK controller with a good tablet. Because: less likely to drop the controller using a tablet & if you do, it is much less likely to break anything.

5. This is project specific. The P4RTK can handle wind VERY well but you have to increase the overlap a bit on windy days.
*For weed detection we mostly fly at 120m for 3cm/px but again, it depends on the job.

6. I recommend leaving camera settings at standard, it makes workflow simple.
When creating our weed detection platform, we ONLY used standard camera settings when training our algorithm. This is becacuse we can't expect end users to have knowledge of photography.

Reach out if you have any questions.

Regards,
Darren

Hey mate,

Thanks very much for the info. I'll forward a link to your app to my mentor, as he's all about software for spot spraying. Are you in Australia or the US?

I'm still waiting for my RTK station to be repaired/replaced under warranty by DJI, and I'm told it may be some weeks, so I'm still waiting there.

I'm a bit new to all of this, so I'll get my mate to help me map out my place the first time. I do like the idea of permanent GCP's on my corner posts. Do I need to make some big black and white checker plates or something to go on top, or can I just paint the top of the posts white or something?

My mate does a lot of spraying in "fruit tree mode" due to the extremely hilly country he works in, but my area is very flat and he says field mode will work fine and the height is checked by the drones radar during spraying.

I've got so much to learn, and start all my license training in a week. I'll report back when I'm flying a bit, even just training flights.
 
Hi Cap,
I'm based in QLD Australia. Would be happy to show you a demo of our platform and discuss how it can be used for your use case.
We haven't done much with spray drones yet but the technology is there to integrate with boom sprays, which all accept the same format.

I've only used RTK mapping. If you're getting your RTK station replaced, I recommend waiting for that & learning as much as you can until then. There is no point trying to use it for this use case without RTK. GCP's are time consuming.


All the best. Talk soon
 

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