Global_position_int

amilcarlucas · May 2, 2018, 11:34am

Hi,

I really want to make sure that the altitude on this message is AMSL. According to common.xml it should be AMSL. To do that I searched the code for GLOBAL_POSITION_INT
and mavlink_msg_global_position_int_send
but I did not find the place in the code where that message gets assembled

Can someone point me to the source file where that message gets assembled ? basically the function call to mavlink_msg_global_position_int_send or something equivalent

Nicolas · May 2, 2018, 11:50am

The mavlink message is sent here:

github.com

PX4/Firmware/blob/71170dce0a87ce06e00d721a713dfc3dc92dfc11/src/modules/mavlink/mavlink_messages.cpp#L1804


			msg.time_boot_ms = gpos.timestamp / 1000;
			msg.lat = gpos.lat * 1e7;
			msg.lon = gpos.lon * 1e7;


			msg.vx = lpos.vx * 100.0f;
			msg.vy = lpos.vy * 100.0f;
			msg.vz = lpos.vz * 100.0f;


			msg.hdg = _wrap_2pi(lpos.yaw) * M_RAD_TO_DEG_F * 100.0f;


			mavlink_msg_global_position_int_send_struct(_mavlink->get_channel(), &msg);


			return true;
		}


		return false;
	}
};


class MavlinkStreamVisionPositionEstimate : public MavlinkStream
{

It is filled with the data from the uorb message, which is published here:

github.com

PX4/Firmware/blob/fbbe1f5288f0e3255b083f8deaaaf2168202a16a/src/modules/ekf2/ekf2_main.cpp#L1152


				vehicle_global_position_s &global_pos = _vehicle_global_position_pub.get();


				global_pos.timestamp = now;


				if (fabsf(lpos_x_prev - lpos.x) > FLT_EPSILON || fabsf(lpos_y_prev - lpos.y) > FLT_EPSILON) {
					map_projection_reproject(&ekf_origin, lpos.x, lpos.y, &global_pos.lat, &global_pos.lon);
				}


				global_pos.lat_lon_reset_counter = lpos.xy_reset_counter;


				global_pos.alt = -lpos.z + lpos.ref_alt; // Altitude AMSL in meters


				// global altitude has opposite sign of local down position
				global_pos.delta_alt = -lpos.delta_z;


				global_pos.vel_n = lpos.vx; // Ground north velocity, m/s
				global_pos.vel_e = lpos.vy; // Ground east velocity, m/s
				global_pos.vel_d = lpos.vz; // Ground downside velocity, m/s


				global_pos.yaw = lpos.yaw; // Yaw in radians -PI..+PI.

Looks like AMSL.

amilcarlucas · May 2, 2018, 12:04pm

Thanks!! That is what I was looking for.