How distance to home is calculated

qczek · June 18, 2018, 9:23pm

Hi,
I develop free available QCZEK LRS RC control system, which provides limited (due to slow downlink) mavlink support and i wonder which messages are required to calculate distance to home value.
Currently only following messages are transfered,

MAVLINK_MSG_ID_HEARTBEAT
MAVLINK_MSG_ID_ATTITUDE
MAVLINK_MSG_ID_GLOBAL_POSITION_INT
MAVLINK_MSG_ID_SYS_STATUS
MAVLINK_MSG_ID_RC_CHANNELS_RAW
MAVLINK_MSG_ID_GPS_RAW_INT
MAVLINK_MSG_ID_VFR_HUD
MAVLINK_MSG_ID_RADIO_STATUS

But it’s not enough for distance to home calculation.
Does Tower need HOME_POSITION msg ( #242 ) to get home position which is stored by FC?
Thank you in advance
Kris

moobsen · June 18, 2018, 10:15pm

Hi,

Interesting project.

While I do not fully grasp the Tower source, I believe yes, it takes the home position from the drone to calculate the distance from home. How else should it calculate the distance to home otherwise?

But see for yourself, I believe this is the relevant part in the Tower source:

github.com

DroidPlanner/Tower/blob/83f62c10282c710709e2bd29bc86530a78b91b42/Android/src/org/droidplanner/android/notifications/StatusBarNotificationProvider.java#L252


    mInboxBuilder.setLine(4, SpannableUtils.normal("Signal:   ", SpannableUtils.bold(update)));
}


private void updateHome(Drone drone) {
    if (mInboxBuilder == null)
        return;


    String update = "--";
    final Gps droneGps = this.drone.getAttribute(AttributeType.GPS);
    final Home droneHome = this.drone.getAttribute(AttributeType.HOME);
    if (droneGps != null && droneGps.isValid() && droneHome != null && droneHome.isValid()) {
        LengthUnit distanceToHome = UnitManager.getUnitSystem(mContext).getLengthUnitProvider()
                .boxBaseValueToTarget(MathUtils.getDistance2D(droneHome.getCoordinate(), droneGps.getPosition()));
        update = String.format("Home\n%s", distanceToHome);
    }
    mInboxBuilder.setLine(0, SpannableUtils.normal("Home:   ", update));
}


private void updateGps(Drone drone) {
    if (mInboxBuilder == null)
        return;

Cheers

qczek · June 20, 2018, 10:11am

Thanks,
I found this piece of code, by i can’t find where mavlink stream is processed, and where high level notifications are send. I expect something like big case, and depending on message type different event is generated… Do you where it’s located in the code?
Thx
Kris