Hi, I am new to flytos and planing to use it for autonomous flight without GPS as I ma using pymavlink for the same purpose. I was wondering if flytos can do the same or not?


Hi @sanchit.gupta, thanks for your interest in FlytOS.

@srv should be able to answer your query accurately.

Indoor positioning and navigation using vision SLAM

You can use FlytOS for autonomous flight. However the autopilot requires a position feedback (from one or more sources such as GPS, optical flow, vicon. etc.) to be controlled (navigation commands) remotely by using pymavlink or FlytOS.

So it’s your choice whether you want to use GPS or other sensor to provide position feedback to autopilot. FlytOS or pymavlink won’t be able to control the drone’s position if position lock is not available. Rather autopilot won’t switch to any position hold mode if position lock is not available.

If you have any sensor which can provide position feedback to autopilot then you are good to go. However for telemetry there’s no restriction of position lock.


Is GPS lock required for only takeoff & land api? For example, if I takeoff manually, setpoint command will work without position lock? (not necessary to be very stable, a little bit drift is acceptable)


As long as you have position lock via GPS, or optical flow or any other sensor, Position setpoint will work.


Thanks Dhiraj for your reply.
Right now I am not using any position lock so the UAV is drifting(obvious).

  1. Could you please tell me how can I send command set mode to without GPS mode?

  2. If I use image tracking (tracking a particular image) would i still need GPS for position hold for avoiding drift?

  3. If I use Lidar or Sonar, do I need to send any specific command?

ps: I tried searching in documentation but couldn’t find anything related to no gps or Lidar based navigation.

Thank you


I didn’t quite get that. Do you mean how to set POS HOLD mode even though no GPS data is available?
Flight modes are controlled by autopilot. If you don’t have GPS lock and have some other sensor, say px4flow then autopilot can be switched to POS HOLD mode without any additional setup (In PX4 firmware, unfortunately I’m not aware of steps in APM). All you need to do is to change your RC stick to POSHOLD mode.
In other words if position fix is available to autopilot through any means (GPS, mocap, optical flow, lidar, etc.) then you can switch it to POS HOLD mode.

Techincally you can not. Theoretically you should be able to stabilize the drone’s position with respect to that of target. But in this case when the position lock is not available the drone wouldn’t go to POS HOLD mode anyway where you can control it’s position. Bit of a chicken egg problem here.

I have not used LIDAR yet for positioning. Neither am I aware of any modules which can be used as position sensor with px4 or APM. Will be happy to hear about if you find anything on this topic.




I had a question about getting position lock purely using an optical flow sensor! I am using a pixhawk px4 along with a pxflow sensor. I have already disabled the preflight check for the gps in QGC, so I am able to arm the drone in manual mode without gps lock. When I try to switch to api mode and arm, I am unable to do so without gps lock. I also tried to unplug the gps completely and followed the same steps. That didn’t work either. Could you let me know what I am doing wrong here!

Thank you!


I am facing the same problem, I use a ZED camera instead of pxflow sensor.


Although it’s obvious, I will mention it once to rule it out. Px4Flow works at a height of min. 1 meter with a clear pattern on the ground. In case you are trying to switch to POS hold when the drone is still on the ground then it will not. Optical flow quality parameter in the telemetry stream will show you current optical flow quality. AFAIK 127 is the minimum quality value for good visual fix. With flow quality below 127, the autopilot will switch back to manual mode.

Apart from this, there are some parameter settings required by autopilot before you can switch to completely vision based pose hold.
@srv-admin Can you please provide more info on autopilot settings for optical flow?

Hope that helps.


@Por_Yu_Kheng Your case could be different. Can you please provide more info?