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Compass Calibration Guide
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<blockquote data-quote="Dronason" data-source="post: 13035" data-attributes="member: 553"><p>Yes, you should but as describe by [USER=18]@msinger[/USER] in this thread, at a clean location.</p><p></p><p>Compass calibration are not really needed often at all. Important is to have a good one. First sign is that your Spark fly with a small angle. If the angle is too big then the Spark will have a conflict between orientation given by the Spark and movement controlled by the GPS. Second there will be the toilet bowl effect and fly away if really poor. Also if you move at some really distant place where the magnetic North is not at same direction as where you calibrate.</p><p></p><p>Cheap drone with only GPS control (no Glonass satellites), poor firmware and mandatory to do always a compass before any takeoff (you do it badly a day or another) result in toilet bowl effect very easily, I had it several time. This guys show it nicely in his video:</p><p>[MEDIA=youtube]2TVOfhwTSIU[/MEDIA]</p><p></p><p>When Spark is hovering, its flight controller will try to make a position correction due to wind drift to bring it where the GPS say it should be. So it will calculate the angle it should adjust the thrust of motors to go to that position but with a compass error (angle difference between the orientation reported by the compass and the real orientation the Spark will move and will be reported by GPS) it will arrive at a wrong position. The next iteration done by the flight controller will also result in an error and it can to start turning around the expected position. Depending on several factors, either it converge finally to correct position or it start to circle with more and more large distance from the correct position.</p><p>In the past, the correction could be done by rotation physically the compass on the drone. Now there are what is called compass calibration. It will allow the Spark to define what is the angle between magnetic North and the Spark structure. Normally the thrust angle difference with the structure is expected negligible. In fact it is the total error between compass North indication and the thrust angle that is important. This is illustrated here:</p><p>[MEDIA=youtube]BfaRpNp-__k[/MEDIA]</p><p></p><p>When the compass angle error is reasonable, it will be not noticeable. If the angle error is larger, you will get instability in hovering (small toilet bowl effect) or even fly away (large toilet bowl effect). The Spark will detect at some point the compass issue and will go for manual control. If it is fare away or you didn't notice that it is no more control under the GPS or there is a lot of wind, it will be difficult to control and bring it back.</p><p>Go4 app indication of compass error at low altitude usually means that Spark is near some metallic stuff. It doesn't mean you must recalibrated but that it should move it away.</p><ul> <li data-xf-list-type="ul">Take off at another location</li> <li data-xf-list-type="ul">Take off on some plastic box</li> <li data-xf-list-type="ul">Move away from car</li> <li data-xf-list-type="ul">Take some altitude</li> <li data-xf-list-type="ul">...</li> </ul><p>As soon you are at some altitude, there is no more interference with metallic part at ground level.</p><p>If you get a compass error at some altitude, it means that you compas really need a good calibration.</p><p>Practice of manual mode (ATTI, no GPS) is important so you are ready if this happens.</p></blockquote><p></p>
[QUOTE="Dronason, post: 13035, member: 553"] Yes, you should but as describe by [USER=18]@msinger[/USER] in this thread, at a clean location. Compass calibration are not really needed often at all. Important is to have a good one. First sign is that your Spark fly with a small angle. If the angle is too big then the Spark will have a conflict between orientation given by the Spark and movement controlled by the GPS. Second there will be the toilet bowl effect and fly away if really poor. Also if you move at some really distant place where the magnetic North is not at same direction as where you calibrate. Cheap drone with only GPS control (no Glonass satellites), poor firmware and mandatory to do always a compass before any takeoff (you do it badly a day or another) result in toilet bowl effect very easily, I had it several time. This guys show it nicely in his video: [MEDIA=youtube]2TVOfhwTSIU[/MEDIA] When Spark is hovering, its flight controller will try to make a position correction due to wind drift to bring it where the GPS say it should be. So it will calculate the angle it should adjust the thrust of motors to go to that position but with a compass error (angle difference between the orientation reported by the compass and the real orientation the Spark will move and will be reported by GPS) it will arrive at a wrong position. The next iteration done by the flight controller will also result in an error and it can to start turning around the expected position. Depending on several factors, either it converge finally to correct position or it start to circle with more and more large distance from the correct position. In the past, the correction could be done by rotation physically the compass on the drone. Now there are what is called compass calibration. It will allow the Spark to define what is the angle between magnetic North and the Spark structure. Normally the thrust angle difference with the structure is expected negligible. In fact it is the total error between compass North indication and the thrust angle that is important. This is illustrated here: [MEDIA=youtube]BfaRpNp-__k[/MEDIA] When the compass angle error is reasonable, it will be not noticeable. If the angle error is larger, you will get instability in hovering (small toilet bowl effect) or even fly away (large toilet bowl effect). The Spark will detect at some point the compass issue and will go for manual control. If it is fare away or you didn't notice that it is no more control under the GPS or there is a lot of wind, it will be difficult to control and bring it back. Go4 app indication of compass error at low altitude usually means that Spark is near some metallic stuff. It doesn't mean you must recalibrated but that it should move it away. [LIST] [*]Take off at another location [*]Take off on some plastic box [*]Move away from car [*]Take some altitude [*]... [/LIST] As soon you are at some altitude, there is no more interference with metallic part at ground level. If you get a compass error at some altitude, it means that you compas really need a good calibration. Practice of manual mode (ATTI, no GPS) is important so you are ready if this happens. [/QUOTE]
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