# ToF detecting phantom obstacles?

Source: https://forum.modalai.com/topic/1972/tof-detecting-phantom-obstacles
Category: General Questions (https://forum.modalai.com/category/2/general-questions)
Posted: 2023-03-21 15:01:09 UTC by hmlow
Replies: 3 · Views: 890

## hmlow · 2023-03-21 15:01:09 UTC

Hi devs

Is it normal for the ToF to detect phantom obstacles?
Might it be caused by certain types of lighting and/or environment?

Im encountering this phenomenon at specific spots (both indoors and outdoors) where it detects an obstacle in front of it when obviously theres is nothing there and PX4's collision prevention kicks in and does not allow it to move forward.

Any advice?

## Reply by wilkinsaf · 2023-03-21 15:14:49 UTC

@hmlow Are you sure that your propellers are out of the way of the ToF camera? 
I have seen issues with that before

## Reply by hmlow · 2023-03-21 15:31:08 UTC (in reply to wilkinsaf)

@wilkinsaf yep they are completely out of the way. Besides, I only encounter this issue at specific spots in some rooms

## Reply by wilkinsaf · 2023-03-21 20:06:17 UTC (in reply to hmlow)

@hmlow 

It might be useful to open voxl-portal and have a look at what the tof is reading when you are seeing this phenomenon. 

If you would like something more in detail you could

1. Would you be able to turn on Computer/Collision Avoidance under sdlog: SDLOG_PROFILE ![6694f651-226f-4b94-8a9f-b0558b76e87a-image.png](https://forum.modalai.com/assets/uploads/files/1679429073812-6694f651-226f-4b94-8a9f-b0558b76e87a-image.png) 

2. recreate the issue
3. verify that PX4 is getting a detection that there is something infront of it through the logs. the message you are looking for is OBSTACLE_DISTANCE