# Depth Information Source Unclear

Source: https://forum.modalai.com/topic/3947/depth-information-source-unclear
Category: Development Drones (https://forum.modalai.com/category/44/development-drones)
Tags: starling2 max, voa, depth sensor, dfs, starling
Posted: 2024-11-16 00:50:58 UTC by griffin
Replies: 2 · Views: 1509

## griffin · 2024-11-16 00:50:58 UTC

Following the [0.9 VOA tutorial](https://docs.modalai.com/voxl-vision-px4-collision-prevention-0_9/) we cannot start up the `voxl-dfs-server` via `systemctl enable` or `start`, it shows enabled but does not run even after restarting the drone.

- Checking in the VOXL portal the VOA point cloud shows that some kind of depth information is being gathered.
- Does DFS occur through some process other than the `dfs-server` in the 1.0+ version of the SDK? Or does the depth information originate from the TOF sensor? 
- The config file from the VOA tutorial is missing / has been renamed to `voxl-vision-hub.conf`, there is a `voxl-vision-hub` process running; is this where depth information is produced in newer SDK versions?

Additionally:

- The `tof_pc` and `tof` views in VOXL portal seems to be rotated s.t. z is forward, y is left and x is down which does not match the NED/FRD frames of the other views. Is this correct?
- The VOXL mapper does not populate on the portal (blank scene) and the mapper service does not appear for `voxl-inspect-services`.

What is the source of depth information on a Starling 2 Max drone with the TOF module?
Any help is appreciated.

## Reply by James Strawson (ModalAI staff) · 2024-11-18 19:59:01 UTC

Hi Griffin,

DFS stands for depth-from-stereo and is only used on the M500 and Sentinel platforms that have stereo cameras.

Starlings use the PMD TOF camera which outputs 3D point points directly from voxl-camera-server. That data is in the reference frame of the camera such that Z points out the lens, X to the right of the image, and Y pointing downwards.

voxl-vision-hub then consumes that data and rotates it based on the mounting location described in /etc/modalai/extrinsics.conf and the current position/orientation of the drone as reported by VIO.

voxl-mapper is not installed by default as it's not part of the core SDK, however it is locally available and can be installed with `apt install voxl-mapper` without needing an internet connection.

Best,
James

## Reply by griffin · 2024-11-19 22:24:36 UTC (in reply to James Strawson)

@James-Strawson 

Hey James,

Thanks for the tip, installing via `apt install voxl-mapper` and then running with `systemctl start voxl-mapper` worked out of the box.

Kind regards,
Griffin