Reach M+ Navio2 + ROS Mavros GPS accuracy

[sundru]

Hello,

Am hoping someone can point me in the right direction. using ReachM+ with Navio2, running ardupilot info sent thru ROS mavros.

Am reading the topic on ROS called “/mavros/global_position/global” to get the Current GPS coordinates. how do i get the current accuracy of these readings (like horizontally accurate to a few meters )?

[wizprod (Christian Grüner)]

Relative or absolute accuracy?
Is the reach m+ set up for RTK? If so, your absolute position accuracy is determined by how well you placed your base-station.

[sundru]

Relative or absolute either would work, i would like to know programmatically that precision being reported now is +/- 1m radius or whatever, so i can do some actions like recording position based on accuracy.

the navsatfix message published has below format , either using this format or other programmatic ways to find accuracy from ReachM+/Navio2 would be great.

http://docs.ros.org/melodic/api/sensor_msgs/html/msg/NavSatFix.html

Also sensor_msgs/NavSatStatus Documentation - can below status be used as in does Navio2 report these correctly ?

Navigation Satellite fix status for any Global Navigation Satellite System

Whether to output an augmented fix is determined by both the fix

type and the last time differential corrections were received. A

fix is valid when status >= STATUS_FIX.

int8 STATUS_NO_FIX = -1 # unable to fix position
int8 STATUS_FIX = 0 # unaugmented fix
int8 STATUS_SBAS_FIX = 1 # with satellite-based augmentation
int8 STATUS_GBAS_FIX = 2 # with ground-based augmentation

Below is the actual ros message being published by mavros

[tatiana.andreeva]

Hi @sundru,

How exactly do you want to determine the precision? Is it enough to get information about solution status only for your application?

You can output the position from Reach in NMEA format. NMEA messages contain information about solution type, HDOP, VDOP, and PDOP. HDOP parameter provides a description of horizontal precision, VDOP - of vertical and PDOP - of position (3D) precision.

So even if there are no ROS topics that fit your requirements, you can write your own topic to get data from NMEA messages.

[sundru]

@tatiana.andreeva

You can output the position from Reach in NMEA format. NMEA messages contain information about solution type, HDOP, VDOP, and PDOP. HDOP parameter provides a description of horizontal precision, VDOP - of vertical and PDOP - of position (3D) precision.

that works thanks ! Another qq , how do I programmatically initiate a navio2 compass calibration (without APM planner) ?

[tatiana.andreeva]

Hi @sundru,

I hardly can advise you something special. You can examine soft- and hard-iron magnetometer calibration algorithms and implement it.