Next up in our “Ask Drone Girl” series is about programming your drone to land at a precise, but different landing point than where it took off from. If you have a question for Drone Girl, contact her here.
Would the DJI drone be able to use the RTK/PPK to land precisely at an ending point (different than the takeoff)?
For example, I’d like the DJI RTK/PPK capability to survey terrain where the drone lands at the other end of the field/swamp onto the roof of my truck. I see this benefit in areas where the drone cannot land safely until it reaches the other side of the field/swamp.
You want to program your drone to takeoff on one side of a field and land on another. It sounds fairly simple, right? It’s possible, to program your drone to set its legs down in a different landing point. But you’ve also introduced another tricky variable: landing on a super precise point — a roof of a car.
This question is kind of a two-parter. Here’s what you have to do to make sure your DJI drone lands in not just a different endpoint, but a precise, small one at that.
Programming DJI drones to land in a different landing point than the takeoff point
DJI drones can complete their mission at a different landing point than the takeoff point.
The simplest option: flying in waypoint mode
Many of DJI’s mid-tier drones (and all their high-end drones) allow you to fly your drone in Waypoint mode. In Waypoint mode, you can pre-record multiple spots in the sky that make up a flight path for your drone. When enabled, the drone will remember those spots, and fly them autonomously, which may be useful if you’re surveying terrain.
However, if you fly in waypoint mode, you need to take one extra step. The default setting is that your drone will return to home (where it took off) when it’s finished with the mission you’ve programmed it to fly. You’ll have to switch it from the default, to either hover (the drone hovers in place until it gets a new, manual command from you, the pilot), land (it lands at the last waypoint) or return to first waypoint (the drone flies to the first waypoint and waits for your next command.
In your case, it might make sense to allow the drone to finish its last waypoint, and then you take control and manually land the drone on your car.
The following drones have a Waypoint intelligent flight mode:
Some pilots use third-party apps such as Litchi to enable waypoints on other DJI drones that don’t already have a Waypoint intelligent flight mode. However, third-party apps are not supported by DJI so use at your own risk. The following drones do not have a Waypoint mode.
For even more customization, use DJI GS Pro to program a different landing point
DJI Ground Station Pro is a free iPad app that allows you to conduct automated flight missions and manage flight data on the cloud.
To use it, you set your required flight zone and camera parameters. The software then automatically generates an efficient flight path. You can set a waypoint flight path with up to 99 waypoints. You can also set end-mission actions. So when your drone finishes its mission, you can set it to either return to home, hover or land (presumably you would tell it to land).
Drones compatible with GS Pro are:
- Mavic 2 Enterprise
- Mavic 2 Enterprise Dual
- Mavic 2 Pro
- Mavic 2 Zoom
- Mavic Pro
- Phantom 3 Standard/4K/Advanced/Professional
- Phantom 4/RTK/Pro/Advanced/V2, and P4 Multispectral
- Inspire 1/Inspire 2
- Matrice 100, Matrice 200 V2, Matrice 210 V2, Matrice 210 RTK V2, Matrice 200/210/210 RTK, Matrice 600/600 Pro, A3, N3
Consider turning off return to home
DJI drones have a feature called “Return to Home.” This is a safety feature, or maybe just a ‘lazy’ feature. If you can’t fly your drone anymore — maybe there was a technical problem, or you feel like you lost control of the drone’s direction and don’t want to fly it even farther away to the point where it loses connection — you may want to press the Return to Home button. As long as the drone’s home point was updated prior to takeoff, DJI drones are able to return to their takeoff point.
In your case though (or cases where drones can’t return to their takeoff point, such as they were launched from a moving boat), you may want to disable return to home.
You can do that in the advanced settings area of the DJI app. Instead of telling your drone to land back at the takeoff point when something goes wrong, you might tell it to land in its current spot. But if that current spot is over a muddy swamp, water or some other unsafe landing spot, you can also just program the drone to hover.
Consider updating the home point manually
If you’re in a situation where you are also moving (ie. you walk alongside the drone during its flight with controller in your hands), you can update the home point manually. Here’s how:
While using the DJI GO 4 app, swipe left on the main screen, press “Home Point: Me,” second, and open the general settings by pressing the three dots on the upper right corner. From there, go to “Main Controller Settings,” and press “Home Point: Me” (it’s that button with a person and home point below).
What is RTK and why you need it for landing on an ultra-precise point
You mentioned that your drone needs to land on the roof of your car. Presumably landing your drone in swampy land is not your ideal. Assuming your car is also parked in that same ultra-precise spot (perhaps it’s a truck you don’t actually drive anymore).
There are plenty of other use cases where drones need to land on an ultra-precise point. Maybe your drone is landing on an automatic charging pad out in a field to boot up for another flight without any human interaction. Maybe you’ve got 1,000 drones in the air for a light show — and when they come down, they can’t land a few inches off, because they’ll land on each other.
For ultra-precise positioning, you probably need to use RTK, which stands for Real-Time Kinematics. RTK is an advanced satellite positioning technique that is supposed to deliver centimeter-level accurate location data.
RTK is generally marketed for drone use-cases like inspections or precision mapping, where every centimeter counts. For example, if you’re conducting a search and rescue mission and looking for lost people over a broad area, it doesn’t really matter if your drone is an inch off. But if you’re making a high resolution, 3D model of the Christ the Redeemer statue in Rio de Janerio, you can’t be a couple inches off, or Christ might end up with an extra finger.
DJI makes drones that are automatically integrated with RTK, like the DJI Phantom 4 RTK. It’s basically a normal Phantom 4, but with the addition of an RTK module integrated into the drone to provide real-time, centimeter-level positioning data. The RTK module can provide positioning accuracy of 1cm+1ppm (horizontal), 1.5cm+1ppm (vertical), and the Phantom 4 RTK can get the 5cm absolute horizontal accuracy of photogrammetric models.
There’s also a redundant GNSS module, intended to help the drone maintain flight stability in signal-poor regions (like some sort of swamp).
PPK won’t help with a precise landing
You mentioned considering PPK. That won’t help you here. PPK, which stands for Post-process Kinematics will help you post-flight, not during flight.
PPK is designed for use in surveying missions that take place in remote areas with poor network signal reception, and/or with obstructions like trees, buildings, or metal structures. PPK software is able to analyze data stored onboard the drone, and calculate where takeoff, in-flight and landing data wasn’t necessarily perfect, but is able to correct those inaccuracies post-flight to build an accurate dataset.
Both RTK and PPK drone solutions are useful for producing centimeter-level accurate data, but while RTK can help you fly with accuracy in real-time, PPK won’t. It only helps you after-the flight. For your purposes, you can ignore PPK.
Is RTK right for you?
In the case of landing a drone on the roof of a car, maybe.
A drone like the Phantom 4 RTK is a powerhouse in precision mapping, allowing you to get centimeter-accurate data while requiring fewer ground control points. But it also has a whopping $6,500 price tag.
That’s an incredible value vs. the cost and effort of traditional GPS for photogrammetry. But in your situation of flying a drone to land on a car, you might not need centimeter-level accuracy. This assumes your car is also parked with centimeter-level accuracy (and let’s face it, it’s not).
If you’re flying automated missions, you might want RTK, but if you don’t need centimeter-level precision, a standard DJI Phantom 4 might be sufficient.
The easiest way to get your hands on the DJI Phantom 4 RTK is through New York-based camera store B&H Photo. The catch? It’s not available for purchase online, so you’ll either have to call them or visit their New York store, in-person.
If a trip to New York isn’t in the cards, you can order the significantly more expensive, $15,000 DJI Phantom 4 RTK with D-RTK 2 Mobile Station, Terra Pro & Accessories Kit. That might be beyond your budget. But hey, at least there’s free 2-day shipping.
If you don’t need centimeter-level precision: save your money. I recommend you fly something like the Phantom 4 or Mavic Pro to take advantage of the intelligence waypoint mode. Once your drone has reached its last waypoint, I advise you set the drone to hover, upon which you can take control and land it on your car.
Readers, what would you advise Emmett do? Leave your thoughts in the comments below!