YDQA cm accuracy

John Dickow: [00:00:00] How we achieve centimeter accuracy with a drone. I, I was trying to do some research myself, and it's a lot more complicated than, say, a setting on your phone or a setting on your

Greg Gradwell: drone. I still don't, it still feels like magic to me, but I feel like I know a couple of the spells and that's really all you need to, to get the benefits of it.

John Dickow: Hello and welcome back to another episode of Your Drone Questions Answered. I'm John Dicko here to find the answers to your drone questions, or at the very least, the person who can. Answer your drone questions. Uh, today I have with me Greg Gradwell. He is a software engineer at pica. Greg, thank you for joining me today.

Yeah,

Greg Gradwell: thanks for having me. So I'm an, uh, aerospace engineer kind of by trade. I've slowly worked myself into the software space just because I wanted to work on autopilots and, uh, more autonomous features with with aircraft. So I'm a software engineer at Pike. I also work, uh, A great deal on kind of the [00:01:00] hardware, hardware and uh, writing firmware, which is how I ended up in the g p s and uh, r t k centimeter level accuracy, uh, area, cuz we've added that, added that to our aircraft.

Can you first

John Dickow: just kind of tell me what centimeter level accuracy is when it comes to drones? So

Greg Gradwell: the typical, just like a regular g p s kind of off the shelf, you'll get maybe one to two meters of accuracy in the horizontal. And maybe, you know, up upwards of 10 meters inaccuracy in the vertical, you know, where they're less accurate in the vertical.

So for some applications, that's just insufficient. So, you know, the nice thing is a lot of inertial navigation systems, um, will, you know, be calculating a position that's more accurate than just the raw g p s, you know, incorporating accelerometers and, and driver scopes and other sensors to kind of fuse those all together.

And give you a better picture, um, than just the raw g p s. But if you really need to know where you are, there are some other methods for giving, you know, so like center media, lab level accuracy is kind of like the, the tagline for about as good as you can expect, um, with, with other methods.

John Dickow: I can imagine that's, that can be pretty [00:02:00] useful in, in certain industries.

What, gimme some examples of how centimeter accuracy is

Greg Gradwell: used. Surveying, if you are, you know, taking like a 3d, do you wanna do a 3D scan? So you're using lidar, so it's very important to know exactly where your drone was at the time of every scan because you're trying to, you know, you can imagine if you're off by, let's say even a meter and.

Uh, you're projecting a beam of light, you know, several hundred meters, uh, that turns into a much larger error or, you know, so, um, that's a big one is, is 3D scans or precision agriculture as well. If you have, let's say, a ground vehicle and you wanna be spraying in a crop and you, you need to know exactly which row you're in.

So if you're a meter off, you might be in a completely different row of your crop. So you wanna really know exactly where you are. Um, and yeah, generally if you're, if you know within a centimeter that's, Pretty good for, for most applications.

John Dickow: Yeah, no, absolutely. And, and when it comes to agriculture, I, I believe you at pica you're doing work actually leading, um, [00:03:00] those type of projects for the agricultural industry.

Is that right?

Greg Gradwell: Yeah, exactly. So, you know, we, we are, we're developing autonomous crop spray, excuse me, crop spraying aircraft as well as, uh, cargo aircraft. Um, so in the air, the, the centimeter level accuracy is, is less needed. You know, we, cuz of course like with an aerial application, we're talking about. On the order of, you know, several meters that are a swath, swath width of what we're spraying.

But, but it's nice. I, I think one of the main advantages we found is we're in countries other than the US where g p s is just not as good. And we were seeing, you know, even more, uh, uh, accuracy. You know, bounds. And so our, our R T K really helped us, uh, bring that in and made our, especially in takeoff and landing, like we know, we wanna know exactly where we are.

So we're on the runway every single time. So anything we can do to improve our solution, uh, is beneficial in, uh, uh, many areas.

John Dickow: Very cool. Very cool. Yeah. And so, kind of getting to the core of the question, I mean, how we achieve centimeter [00:04:00] accuracy with a drone? I, I was trying to do some research myself and it's a lot more complicated than say, a setting on your phone or a setting on your drone.

I mean, it's, it's pretty involved. And you mentioned things like r t K and so go ahead, kind of explain to me how centimeter level, uh, accuracy is a, is achieved, the

Greg Gradwell: reason we can only get one to two meters, uh, you know, of accuracy. For just a traditional GPS is that, you know, so we're getting essentially signals radio waves from satellites in space and those radio waves are traveling through the atmosphere.

And I think particularly the ionosphere is the most, provides the most kind of, uh, disturbance. And the timing is a very important for those waves. So if they don't have this direct path, uh, then the, you know, your receiver can't know exactly how long it took for to get from the satellite to your receiver and that, that's basically how we're.

Um, calculated how the GPS is calculating its position. So what we need to do after the fact, what we're able to do is if we know where the satellites were at the [00:05:00] time that they sent those signals, uh, we can either kind of compute, uh, some of the errors or remove some of the errors in real time, which is r t K.

So if that stands for realtime kinematic, or we can do it even better after the fact, which is P P K or post-process kinematic. So if you're doing like a scan, let's see, you want to have like a 3D scan of an area. P P K might be perfectly sufficient where you just, you fly without any sort of augmented G P s, but then after the fact, you can, from some sort of service, can know exactly where the satellites were.

They can do this post-processing and then kind of correct all of your positions to a much more precise. Uh, value. And that's one way to get centimeter level accuracy, um, with pica. And a lot of, I think, um, like if you're spraying a crop, of course you need to know exactly where you are in real time. It doesn't matter after the fact, right?

And so, uh, I think R T K is a more common. Um, more common solution, especially cuz it's, you don't need to rely on a, a third party to [00:06:00] process your data and it's gotten much more accessible in the last couple years. And so I'd love to talk about the ways that you can get r t k on your drone, uh, right now for not too much money.

John Dickow: That was my next question is how, what is needed? How do you get there?

Greg Gradwell: First of all, you need a GPS receiver that is capable of, of processing, you know, this, these R T K corrections. So I think the most common one that I've seen now is, um, manufactured by U Blocks. It's the Zed F nine P, so the Z E D F nine P.

And you see that kind of popping up everywhere. So I, you know, I'm not sure for a lot of the commercial. Um, kind of off the shelf drones, how how many of them specify which receiver is, is being used, but generally they will say if they're, you know, capable of R T K or not. The, the cool thing is, is that these receivers are doing all the corrections on, on board.

Like you just need to feed them this correction data, which we can talk about, and, and they do all the calculations. And that wasn't the case, you know, three years ago, five [00:07:00] years ago. Uh, so that's what's so exciting now. It's like you don't even really need to know how it works. You just need to know what you need to give the receiver and it'll take care of everything.

John Dickow: Okay. And so you mentioned yeah, feeding the, the correct, the collection data. I mean, is that something that's easy to do or do you need

Greg Gradwell: some know-how It's not terribly complicated. Um, it, it's kind of one of those things I think that you. You're gonna kind of iterate on your level of understanding. You know, first you like, you'll read about it and you're like, oh, I think I kind of get it.

And then you'll be like, actually, I don't understand about 90% of it. But like the, the more you just kind of read, uh, some articles, um, spark Fund has a really great, uh, kind of tutorial about how to set up. A, a base station to, to get R T R T K corrections. I still don't, it still feels like magic to me, but I feel like I know a couple of the spells and that's really all you need to, to get the benefits of it.

Yeah. So essentially if you want R T k, what you need is some sort of base station that is going to publish, uh, corrections. And these corrections are in the form of R TCM messages. So there's a [00:08:00] handful of messages that will go from a, a base station to your rover. So those are kinda like the two terminologies we'll use, like the base is a fixed.

A fixed receiver and the rover is whatever's moving around, uh, you know, on your drone. And the Bay Station is this known at a known position. So there are a number of ways you can do this. You can either, um, there are many, um, bay stations that are set up, either like as government, you know, there'll be like government organizations or research organizations that have their own base stations cuz they, they need the corrections and they're publishing them.

Um, or you can set up your own. It's, it's really easy if you just have a second, uh, GPS receiver. You, um, you can record data for a, a certain amount of time. I mean, even a few hours will get you, um, close enough. And so collecting that data over, over a long period of time, you're able to post process that data.

Um, there's a couple organizations that that will do that. You wanna know where your base station is. Within, let's say a couple centimeters, basically, whatever accuracy you have with your base [00:09:00] station, you can get, should be able to get that with, with your drone. And so the idea being that if your base station knows exactly where it is, and you will, you will tell the, the receiver, um, either you can post-process it, you know exactly where it is, or the, the uBlock receivers have a, a mode called Survey Inn.

Where they will just, they know that they're supposed to be a Bay Station. They'll try to, uh, estimate their accuracy to a certain threshold. As soon as they know that they lock in, they say, okay, this, here's where I am in space. Therefore, any, any, basically if, if I, any, um, g P S signals that I get that tell me that I'm somewhere else, I know that that's an error, or I can assume that's an error.

So they're able to calculate these corrections from each satellite. Because they say, I know where I am. You're trying to tell me that I'm a little bit over here, but I'm not. So that must be from the errors that we've, you know, have come through the atmosphere. So that's how they calculate and, and they'll produce these r TCM messages.

You want your base station. Uh, the, the antenna should have, you know, you want it to have [00:10:00] good view of the sky. It should be, um, Basically, yeah. Any errors that are in your base station will be propagated to your rover. So if you don't have a great base station solution, like you're just gonna see that, that, uh, that error is propagated.

Uh, if you used the survey in mode. So that's, if, let's say I, I go to somewhere, I'm going, I'm flying somewhere new and I am just gonna be there for the day. But I do want to have centimeter level accuracy while I'm there. So you'd use that survey in mode, you'd set up, so I use like a tripod for my antenna, so it's in a fixed spot.

I let it run. I mean, it takes, I mean, a matter of minutes. If you've got a good, good view of the sky with, with a nice antenna and it, it basically, it will, it will fix its position. You won't, you won't have absolute centimeter level accuracy. From that mm-hmm. From that base station, but you'll have like relative centimeter level accuracy.

So it, because like we said, the base station will only know where it is within a couple meters. You know, it, it's still got all the inherent GPS inaccuracies because, you know, again, it's got, it's got that centimeter level accuracy, just not in the absolute sense. So, okay. [00:11:00] This might not be great if you are, um, if you're trying to map something like.

If you're getting the 3D scan, you, you really need that absolute accuracy. If I wanna say I, I wanna locate something on a map, I wanna know exactly where it is in, in 3D space. Um, the survey in mode might not be sufficient. Um, but if you just want to have like a, your vehicle performing much better than it.

Than it might normally like if you want to have your drone hovering perfectly in place, uh, you know, then that relative accuracy would be sufficient at, at Pica we do, you know, we we're flying at, at airfields, we know we're gonna be there for a long time. So like the first thing we do when we go to a new spot is we will get a fixed base station location.

And then we just set that and every time we fly, it knows exactly where it is. There's no, you know, you don't have to do that every time. Where would

John Dickow: somebody find like a base station? How can you get one and or even the antennas, are those just things that you acquire online from certain

Greg Gradwell: sites? Yeah, so I mean, spark Fund's a great place to look.

Um, there's a company called Arju Simple, um, that's in Europe. Uh, we can link to that. That's, they've got a lot of great tutorials. [00:12:00] Um, and they're, a lot of their products are, um, intended for, I mean, it's basically just to get R t K more accessible is extremely affordable. These, you know, these receivers are on the order of a couple hundred dollars, which is just.

In order of magnitude less than I think, you know, it cost five years ago to get R T K. The nice thing is your bay Station could be the same exact receiver that you have in your rover, which makes things really easy. So you're only familiar with, you know, you only need to be familiar with one. The GPS receiver, um, and U Blocks has software to, to configure them.

Uh, again, they're, they're many tutorials like RJ Simple has configuration files that you can just download and you say, okay, I've got, I wanna make one of these receivers my base and one my rover, and they've got. Configuration files ready, that you just use the software to upload directly. So like you could really hardly know anything about it and, and, and get a, a solution working.

Um, the key is that you need some way of transmitting the corrections from your base to Year Rover. So, [00:13:00] okay. Um, I think, you know, probably the easiest way is just a, a point to point link. So like an XB radio or something. Uh, and RJ simple, they have basically all their kits have headers to, you can just slap on an XB radio.

I mean, they sell, they sell kits that are ready to go. You could, you could just one stop shop. They'll sell you the, the base and the rover with the xbs configured to talk to each other. So like you, it's practically plug and play. I mean, for under a thousand dollars you can have RTK out of the box, which.

It's just, I mean, it seems crazy to me. It's, it's fantastic. Yeah.

John Dickow: That's so much more accessible than I would ever imagined. And so that's, that's really cool. Do you think it's only gonna become more accessible into the future as things

Greg Gradwell: continue to develop? I don't see why not. Um, I think as the, the receivers get cheaper, uh, and as you know, as more people buy 'em and it becomes more popular, so yeah, go out there and buy some, so the prices come down so we can all get the benefits.

If you don't want to have a base station, you can leverage one of these existing ones. Uh, RTK to Go is a great site, uh, that works with that. Basically it shows you they're, they're called casters, so it's essentially like a fixed base station that is publishing [00:14:00] data to, um, To a server, and then you can use, if you have internet access, you can then retrieve those corrections.

The, the catches that you have to be within roughly 35 kilometers, I think is kind of the, the, the number I see with, you know, you have to be near enough that caster so that the corrections will still apply to your rover, but there's a number of free, you know, free ways to just get correction data. Uh, if you didn't want to have your base station,

John Dickow: Again, accessibility.

I'm just so surprised that they're, you know, that this is, anyone can really do this. It's

Greg Gradwell: wild. It's so cool.

John Dickow: Well, Greg, thank you so much for coming on and explaining this to me. I really appreciate it. To our audience, you can submit your own drone questions, uh, at yd q a.io. I'll do my best to find the answer to it, or again, find the person who can answer to it.

Uh, in the meantime though, we'll see you in the sky.