Sending x, y, z coordianates in meters to flight controller

ArduCopter
,
1

Hello,
I would like to replace GPS, by sending coordinates as x, y, z in meters.
Right now I am getting the best results by converting the coordinates to lat, lon, alt and sending it as GPS_INPUT mavlink message. But the drone is still drifting about 0.2-0.5 m. I am also obtaining yaw angle from arcus tangent of 2 UWB sensors located on drone. The UWB accuracy should be around 10cm.

I know there is the message VISION_POSITION_ESTIMATE, but it requires the roll and pitch angles which i don’t have. When I am sending 0 for them I am getting an error that IMU stopped aiding.

Thank you for any help

2

If someone is wondering how to convert meters to gps coordinates here is an example from mavsdk(link):

CoordinateTransformation::global_from_local(LocalCoordinate local_coordinate) const
{
    const double x_rad = local_coordinate.north_m / world_radius_m;
    const double y_rad = local_coordinate.east_m / world_radius_m;
    const double c = sqrt(x_rad * x_rad + y_rad * y_rad);

    GlobalCoordinate global{};

    if (fabs(c) > 0) {
        const double sin_c = sin(c);
        const double cos_c = cos(c);

        const double ref_sin_lat = sin(_ref_lat_rad);
        const double ref_cos_lat = cos(_ref_lat_rad);

        const double lat_rad = asin(cos_c * ref_sin_lat + (x_rad * sin_c * ref_cos_lat) / c);
        const double lon_rad =
            (_ref_lon_rad +
             atan2(y_rad * sin_c, c * ref_cos_lat * cos_c - x_rad * ref_sin_lat * sin_c));

        global.latitude_deg = to_deg_from_rad(lat_rad);
        global.longitude_deg = to_deg_from_rad(lon_rad);

    } else {
        global.latitude_deg = to_deg_from_rad(_ref_lat_rad);
        global.longitude_deg = to_deg_from_rad(_ref_lon_rad);
    }

    return global;
}

After that you need to send mavlink message of type GPS_INPUT:

	mavlink_message_t msg;
	uint16_t len = mavlink_msg_gps_input_pack(
		1, 0, &msg,
		micros(),
		0, //Gps ID
		IGNORE_FLAGS_MV_GPS,
		time_week_ms,
		time_week,
		3,		//Fix Type,	
		lat_int, lon_int,
		alt_int,			// altitude
		0,	// HDOP,
		0,	// VDOP
		0.0f,	// Vn
		0.0f,	// Ve
		0.0f,	// Vd
		0.0f,	// Speed accuracy
		0.0f,	// Horizontal accuracy
		0.0f,	// Vertical accuracy,
 		14,		// Satellites visible
		yaw
	);

	mavlink_msg_to_send_buffer((uint8_t*)io_buff, &msg);
	ser.write(io_buff, len);

And set couple of parameters:
GPS_TYPE - MAV
COMPASS_ENABLE - 0
COMPASS_USE - 0
COMPASS_USE2 - 0
COMPASS_USE3 - 0
EK3_SRC1_POSXY - 3 (GPS)
EK3_SRC1_POSZ - 3 (GPS)
EK3_SRC1_VELXY - 0 (None)
EK3_SRC1_VELZ- 0 (None)