Dawn Precision Landing, an overview



Dawn's default precision landing behavior



Dawn ships with an app that engages Dawn's precision landing features under two conditions:


1) Your craft enters landing mode

2) Your craft starts a landing waypoint in mission mode


These triggers are easy to edit and modify yourself, and this default app is less than 100 lines of python and completely open source.


If Dawn does not detect a landing pad it will land in-place. Dawn will land unless something blocks its path, or the area it is landing on is unsafe - contains for example; trees, uneven ground etc. The default behavior in this app is not to perform a search for the pad or a safe landing spot, but a search can easily be commanded by editing the app and using our API. More details and documentation on this are coming soon!


If Dawn does find a pad it will perform a landing on the pad, while pausing if obstacles block its path. Dawn lands with a default accuracy of 0.5m, though this is configurable using our API.


DAWN REQUIRES A 2m RADIUS AROUND THE PAD TO BE COMPLETELY EMPTY. If objects or people are in this area Dawn will not land. If obstacles are close to 2m from the pad it may take dawn 20 - 30 seconds before it has built up enough confidence to begin a landing. This radius is configurable from within the API as well, though we strongly recommend keeping it 2m or greater.






This is an example of a landing area where obstacles are close to 2m from the pad. In this case the closest obstacle is a tree roughly 2.2m from the pad. In this scenario Dawn hovers above the pad for about 15 seconds before it is sufficiently confident that it can perform a landing. If you need Dawn to perform a fast landing it is important to make sure the landing pad is 3m or more from the closest obstacles. If people get in the way it may take another 15 seconds before Dawn will land after the people leave the landing site.



Troubleshooting guide



Dawn does not land, and instead hovers still above the pad



This is likely the result of obstacles being too near the landing pad. Check the Dawn logs and see if there are repeated messages that note that obstacles are blocking the landing path. If not it may be the case that Dawn does not have sufficient control over your craft, if you do not see messages about obstacles blocking your landing follow the troubleshooting section below.



Dawn oscillates above the pad and does not descend, or intermittently ascends and descends



This is very likely to be the result of a poorly tuned controller. Dawn uses the control system built into-px4. If you see this behavior you should follow guides online for tuning the position control system of px4. If px4 is following Dawn's setpoints closely and it is not a control issue it is very likely the result of either a poor gps fix or bad compass calibration. If this is the case follow the troubleshooting section below.



Dawn oscillates in z or flies unpredictably



Check your gps fix and compass calibration. Make sure that a regular landing with Dawn disabled lands smoothly and correctly. Dawn has careful safety mechanisms that prevent it from ever being overly aggressive in control, if you experience aggressive control behavior it may be either a GPS/ Compass issue or the result of excessive vibrations in your frame.



Dawn does not detect the pad



This is most commonly the result of craft vibrations shaking the cameras violently. Even though Dawn uses Global Shutter cameras, excessive vibration can still heavily impact system performance.





Here is an example of strong vibrations in the craft frame. Pull the Dawn logs and make sure the camera images are clean and crisp.





Example of a low vibration image under the same scene conditions. Even when Dawn is moving there should be little to no blur in the images. If there is, it may be an indication that vibrations are present in your frame.



Any other problems



If you are experiencing issues that are not on this page or you find this information to be unhelpful in any way please get in touch with us. We support clients in six continents, and are available to resolve issue at any time.