# Better choice in GPS denied flight: Offboard or Mission?

**URL:** <https://discuss.px4.io/t/better-choice-in-gps-denied-flight-offboard-or-mission/32998>\
**Category:** PX4 Autopilot\
**Created:** [June 30, 2023, 3:08am UTC](https://discuss.px4.io/t/better-choice-in-gps-denied-flight-offboard-or-mission/32998 "2023-06-30T03:08:22Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![chuck00lin](https://discuss.px4.io/letter_avatar_proxy/v4/letter/c/4da419/32.png) [@chuck00lin](https://discuss.px4.io/u/chuck00lin)\
**Post date:** [June 30, 2023, 3:08am UTC](https://discuss.px4.io/t/better-choice-in-gps-denied-flight-offboard-or-mission/32998/1 "2023-06-30T03:08:22Z")

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Hello,

I am currently working in a GPS-denied environment and exploring the usage of PX4 with external vision sources and optical flow. I initially attempted to use QGroundControl to create mission scripts. However, I noticed that the missions only functioned in simulation and not in the real world.

- I was wondering if Mission mode requires a GPS signal to operate. Is it possible to utilize mission mode with an external vision system?

- Additionally, I attempted to switch to Offboard mode while connecting PX4 through MAVROS, but I encountered difficulties in doing so. Are there any preconditions or specific requirements for using Offboard mode?

I would greatly appreciate any recommendations regarding the appropriate choice between these modes.

my setup:  
ROS2  
PX4 1.13  
MAVROS

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**Author:** ![mdobrea](https://discuss.px4.io/user_avatar/discuss.px4.io/mdobrea/32/7568_2.png) [@mdobrea](https://discuss.px4.io/u/mdobrea)\
**Post date:** [July 2, 2023, 7:09pm UTC](https://discuss.px4.io/t/better-choice-in-gps-denied-flight-offboard-or-mission/32998/2 "2023-07-02T19:09:44Z")

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Some preconditions to switch to Offboard mode:

1. The vehicle must be armed before this mode can be engaged.
2. The vehicle must be already be receiving a stream of target set-points (\>2Hz) before this mode can be engaged. The vehicle will exit the Offboard mode if target set-points are not received at a rate of \> 2Hz.
3. This mode requires position or pose/attitude information - e.g. GPS, optical flow, visual-inertial odometry, mocap, etc.

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**Author:** ![chuck00lin](https://discuss.px4.io/letter_avatar_proxy/v4/letter/c/4da419/32.png) [@chuck00lin](https://discuss.px4.io/u/chuck00lin)\
**Post date:** [July 3, 2023, 9:16am UTC](https://discuss.px4.io/t/better-choice-in-gps-denied-flight-offboard-or-mission/32998/3 "2023-07-03T09:16:56Z")

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Thanks for your reply. I believe my question arises from a lack of understanding regarding Offboard Mode.

Additionally, do you know if it is possible to use Mission Mode without a global position? I haven’t been able to find any documentation mentioning this.

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**Author:** ![mdobrea](https://discuss.px4.io/user_avatar/discuss.px4.io/mdobrea/32/7568_2.png) [@mdobrea](https://discuss.px4.io/u/mdobrea)\
**Post date:** [August 17, 2024, 3:03pm UTC](https://discuss.px4.io/t/better-choice-in-gps-denied-flight-offboard-or-mission/32998/4 "2024-08-17T15:03:51Z")

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I have no practical experience, so I make a supposition that is not possible … but I can be wrong also.