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Correct RTK fused position topics (M300)
385 6 1-19 15:45
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nzaccardi-at
lvl.1

United States
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What is the correct Telemetry topic to use for RTK fusion data that is >5Hz (preferably 50hz) on an M300? I would like to have accurate Lat / Lon / Altitude / Heading. I'm aware of these methods for accessing GPS data when using the telemetry system:


- TOPIC_ALTITUDE_FUSIONED

- TOPIC_ALTITUDE_BAROMETER <- Inaccurate

- TOPIC_GPS_FUSED

- TOPIC_GPS_POSITION <- Mostly correct using RTK as baseline, up to 5m difference from RTK

- TOPIC_RTK_POSITION <- Most accurate

- TOPIC_RTK_YAW <- Seems to be most accurate

- TOPIC_COMPASS <- Very inaccurate


Ultimately this will be used in connection with a joystick command or a posAndYawCtrl command so connecting those values to what would be passed to those two functions would be helpful.

For example, posAndYawCtrl seems to base the altitude on broadcast data. Newer versions seem to use joystick comamnds but still rely on broadcast. This is relatively confusing for altitude because pasAndYawCtrl is an absolute value not an offset.

Any help would be appreciated!

NZ


1-19 15:45
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kv886
Second Officer

South Africa
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I think it is the TOPIC_RTK_POSITION. Because only this topic can get RTK position.
1-21 03:07
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nzaccardi-at
lvl.1

United States
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The problem with TOPIC_RTK_POSITION is that it is only 5hz which is insufficient for positional movement commands which should be updated at 30Hz otherwise the motion can be erratic. 5Hz is slow.
1-21 04:46
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fans88f98038
lvl.1
Flight distance : 126955 ft
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United States
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Did you try TOPIC_POSITION_VO which support 50Hz update frequency.
This topic fused  IMU, VO, GPS(if available), RTK (if available), ultrasonic, magnetometer, barometer all these sensor data.   

* @note Since this topic relies on visual features and/or GPS, if your environment does not provide any of these
* sources of data, the quality of this topic will reduce significantly. VO data quality will reduce if you are too high
* above the ground. Make sure that the Vision Positioning System is enabled in DJI Go 4 before using this topic
* (by default it is enabled).
1-21 10:10
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nzaccardi-at
lvl.1

United States
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I did implement something using VO however that is not a workable solution for us because the we are flying in open space and have no visual feedback.
1-27 09:28
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djiuser_evs0J1OtFS5U
lvl.2

Spain
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Any news?
I have come to the same conclussion, there is no way to do smooth control of an autonomous flight using the RTK_POSITION since its frequency. I thought that the topic GPS_FUSED would use the RTK information if available. How does DJI achieve precise flying with the rtk then?
7-14 02:59
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nzaccardi-at
lvl.1

United States
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We did indeed use RTK_POSITION however we needed to do our own fusion and control loop to make it work.  I'm happy to connect with you and discuss the solution if that is helpful. PM me your email and we can connect.

NZ
7-14 06:39
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