# Toy/hobbyist quad copters - what coordinate systems? **URL:** \ **Category:** Factual Questions\ **Created:** [April 9, 2014, 2:17am UTC](https://boards.straightdope.com/t/toy-hobbyist-quad-copters-what-coordinate-systems/685684 "2014-04-09T02:17:51Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [April 9, 2014, 2:17am UTC](https://boards.straightdope.com/t/toy-hobbyist-quad-copters-what-coordinate-systems/685684/1 "2014-04-09T02:17:51Z")
Those quad rotor flying devices that sell for below $100 these days - I mean for example the ones you see if you search for “quad copter” on Amazon - what coordinate systems do they use? Do you control them in geographic coordinates in terms of North, South, East and West? Or do you control them in polar coordinates from yourself in terms of Closer, Further, to my Left and to my Right? Or do you control them in terms of the coordinate system of the device itself, so the copter would have a front and a rear, and you would tell it go forward, back up, move to copter’s left, or copter’s right? And in this last case, you have to be able to see how it is oriented to know how to work the controls, right? And how about up and down, are there any different versions of that? Do copters understand how to keep themselves facing the operator, for instance, while moving around? Do they come with selectable coordinate systems? ---
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [April 9, 2014, 2:32am UTC](https://boards.straightdope.com/t/toy-hobbyist-quad-copters-what-coordinate-systems/685684/2 "2014-04-09T02:32:27Z")
You’re not asking about a coordinate system as much as a control scheme. The product description or videos will usually let you know how they’re controlled. And it really just depends. The [cheaper ones](http://www.amazon.com/UDI-2-4GHz-RC-Quadcopter-Camera/dp/B00D3IN11Q/ref=sr_1_1?ie=UTF8&qid=1397010345&sr=8-1&keywords=quadcopter) move around like RC cars… moving in different directions relative to its current position, with you controlling it via an RF remote. The cheap ones don’t really know where they’re going and at most they self-stabilize to level flight while waiting for your input. At the cheapest levels they’re unlikely to have a real-time video feed either. If you [spend more money](http://www.amazon.com/Parrot-AR-Drone-Quadricopter-Controlled-Android/dp/B007HZLLOK/ref=sr_1_1?ie=UTF8&qid=1397010348&sr=8-1&keywords=Parrot+AR), you can get drones that feed you real time video to either a headset, a dedicated video unit, or a smartphone/tablet. Beyond that, you can also get [self-piloting drones](http://www.amazon.com/DJI-Phantom-Quadcopter-Integrated-Camcorder/dp/B00FW78710/ref=sr_1_1?ie=UTF8&qid=1397010698&sr=8-1&keywords=GPS+quadcopter) that have built-in GPS. You create waypoints for it beforehand, upload the journey, and then it’ll take off and fly where you tell it to, maybe with a video camera attached, and go from GPS waypoint to waypoint. The more expensive ones usually also let you take over and fly manually if you so choose. But the cheaper ones can’t fly along a GPS route because it has no hardware or software for that, and likewise can’t give you a video feed without a camera and some sort of wireless transmitter. If you DIY this stuff (there’s a huge community out there), you get to pick your own control scheme(s). ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [April 9, 2014, 2:33am UTC](https://boards.straightdope.com/t/toy-hobbyist-quad-copters-what-coordinate-systems/685684/3 "2014-04-09T02:33:15Z")
> **[How to Fly a Quad Copter](https://www.instructables.com/How-to-Fly-a-Quad-Copter/)** > > How to Fly a Quad Copter: Do you need a new hobby?  Want to fly?  There are multiple instructions about how to make a quad-copter, but what about if you want to fly it as well?  I am going to show you all the necessities to be able to... [http://www.researchgate.net/publication/228808757\_Quadrotor\_helicopter\_flight\_dynamics\_and\_control\_Theory\_and\_experiment/file/9c960526569f1826e2.pdf](http://www.researchgate.net/publication/228808757_Quadrotor_helicopter_flight_dynamics_and_control_Theory_and_experiment/file/9c960526569f1826e2.pdf) (PDF warning) ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [April 9, 2014, 3:00am UTC](https://boards.straightdope.com/t/toy-hobbyist-quad-copters-what-coordinate-systems/685684/4 "2014-04-09T03:00:45Z")
Wow. Nice info! Nice links, both of you! I especially liked the paper at the last link (the pdf warning) and its discussion of blade flapping. I wondered about that. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [April 9, 2014, 4:02am UTC](https://boards.straightdope.com/t/toy-hobbyist-quad-copters-what-coordinate-systems/685684/5 "2014-04-09T04:02:38Z")
> [@Napier](#): > > Do they come with selectable coordinate systems? Some do. Mine can orient itself so that “forward” goes forward with respect to the body, or north (using GPS or compass as a reference), or directly away from the operator (conversely, “back” will bring the 'copter back towards you). ---
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [April 9, 2014, 4:52am UTC](https://boards.straightdope.com/t/toy-hobbyist-quad-copters-what-coordinate-systems/685684/6 "2014-04-09T04:52:27Z")
> [@Dr.Strangelove](#): > > Some do. Mine can orient itself so that “forward” goes forward with respect to the body, or north (using GPS or compass as a reference), or directly away from the operator (conversely, “back” will bring the 'copter back towards you). What’s “you” in this case? Is it a pre-set coordinate, or does it track your body/your controller somehow? ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [April 9, 2014, 5:05am UTC](https://boards.straightdope.com/t/toy-hobbyist-quad-copters-what-coordinate-systems/685684/7 "2014-04-09T05:05:33Z")
> [@Reply](#): > > What’s “you” in this case? Is it a pre-set coordinate, or does it track your body/your controller somehow? As it’s set up now, mine takes a GPS reading upon takeoff, and then assumes I’ll stick around near the launch point. It’s also possible to send my GPS coordinates via the telemetry system, but I haven’t used that feature yet. It would involve hooking up the telemetry transmitter to my phone or other GPS-capable device. ---
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [April 9, 2014, 5:09am UTC](https://boards.straightdope.com/t/toy-hobbyist-quad-copters-what-coordinate-systems/685684/8 "2014-04-09T05:09:38Z")
> [@Dr.Strangelove](#): > > As it’s set up now, mine takes a GPS reading upon takeoff, and then assumes I’ll stick around near the launch point. It’s also possible to send my GPS coordinates via the telemetry system, but I haven’t used that feature yet. It would involve hooking up the telemetry transmitter to my phone or other GPS-capable device. Fascinating. In this scenario, where “forward” means “away from you”, does holding down “left” mean it’ll fly in a straight line perpendicular to “forward” (instead of turning left in circles like a car might)? ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [April 9, 2014, 5:20am UTC](https://boards.straightdope.com/t/toy-hobbyist-quad-copters-what-coordinate-systems/685684/9 "2014-04-09T05:20:21Z")
> [@Reply](#): > > Fascinating. In this scenario, where “forward” means “away from you”, does holding down “left” mean it’ll fly in a straight line perpendicular to “forward” (instead of turning left in circles like a car might)? Good question. I don’t use the mode much and so I’m not actually sure, but I _think_ the answer is that it goes counterclockwise at a fixed distance from the origin point. However, what I’m sure of is that the 'copter doesn’t rotate on its own axis. It doesn’t care which way it points since all directions are symmetrical. It always knows which way north is, and can travel equally well in any direction relative to that no matter what the orientation. There is a separate control which allows it to rotate in place (in case you need to aim a camera, for instance).