# Fuse altitude measurements to state estimate

Source: https://forum.modalai.com/topic/154/fuse-altitude-measurements-to-state-estimate
Category: VOXL SDK and Software (https://forum.modalai.com/category/47/voxl-sdk-and-software)
Tags: ekf2, range finders, altitude
Posted: 2021-03-11 10:28:42 UTC by LucasW
Replies: 2 · Views: 1906

## LucasW · 2021-03-11 10:28:42 UTC

I would like to send altitude data produced by embedded, downward-looking range finders (VL53l1X and teraranger evo 60m) to the auto-pilot. I would like to do it over mavros since I already have interfaced the sensors over ROS (connected to voxl I²C port 7).

Should I try to use the [`/mavros/vision_pose/pose topic`](https://docs.px4.io/master/en/ros/external_position_estimation.html#relaying-pose-data-to-px4)? There are also several PX4 parameters (`EKF2_RNG_*`) that have to be set (defining when to use the range finders, e.g. at takeoff and while landing), but I am not sure if those parameters are supposed to work only with supported flight controller hardware when connecting specific range finders directly to them.

Long story short, I haven’t found a clear way of publishing altitude data over mavros to let the EKF2 fuse this information into the state estimate. Any hint?

## Reply by Chad Sweet (ModalAI staff) · 2021-03-11 22:06:44 UTC

Hi Lucas, I don't think we have any experience with this. Have you tried the PX4 EKF topic at px4.slack.com?

## Reply by LucasW · 2021-03-15 11:48:19 UTC

I do not think I have access to this slack. It seems restricted to a few specific people only. But I tried their [forum](https://discuss.px4.io/). Thanks anyway!