Help: ZED depth camera annotation error problem

zhangYQHBAU · September 10, 2024, 7:45am

When I used the ZED camera, I used the depth camera and the color image for the combination of positioning errors. The distance of about 1m has an error of 2-4 cm. What causes this?
My operation is as follows:
Open the image node in ZED_ROS_Wrapper.
First, we obtained the color image information after the left eye correction, and then marked the (u, v) coordinates in the image.
The depth information is then obtained using /zed/zed_node/depth/depth_registered"

According to (u, v) and the depth information obtained, the corresponding three-digit distance information is calculated: the formula is as follows;
mmexport1725954207144

But the error calculated by the problem city is very large, about 0.7m-1.5m within the range of 3-4 cm error, may I ask why the city? Thank you!

Myzhar · September 10, 2024, 7:48am

Hi @zhangYQHBAU
what type of surface are you looking at? Is it texturized?
What Depth mode are you using? Is it the default PERFORMANCE?

zhangYQHBAU · September 10, 2024, 8:02am

This is the type of surface that I am looking at.

Can the depth mode be modified in ZED_ROS_Wrapper? I didn’t focus on that metric.

Myzhar · September 10, 2024, 8:15am

You have a lot of parameters to tune to obtain the configuration that better fulfills your requirements:

github.com

stereolabs/zed-ros-wrapper/blob/master/zed_wrapper/params/common.yaml

# params/common.yaml
# Common parameters to Stereolabs ZED and ZED mini cameras
---

# Dynamic parameters cannot have a namespace
brightness:                     4                               # Dynamic
contrast:                       4                               # Dynamic
hue:                            0                               # Dynamic
saturation:                     4                               # Dynamic
sharpness:                      4                               # Dynamic
gamma:                          8                               # Dynamic - Requires SDK >=v3.1
auto_exposure_gain:             true                            # Dynamic
gain:                           100                             # Dynamic - works only if `auto_exposure_gain` is false
exposure:                       100                             # Dynamic - works only if `auto_exposure_gain` is false
auto_whitebalance:              true                            # Dynamic
whitebalance_temperature:       42                              # Dynamic - works only if `auto_whitebalance` is false
depth_confidence:               50                              # Dynamic
depth_texture_conf:             100                             # Dynamic
point_cloud_freq:               10.0                            # Dynamic - frequency of the pointcloud publishing (equal or less to `grab_frame_rate` value)

This file has been truncated. show original

You can find a detailed description of each of them on the online documentation.

zhangYQHBAU · September 10, 2024, 9:38am

Thank you very much for your reply, I will do an experiment to verify it right away!

zhangYQHBAU · September 10, 2024, 9:40am

I would like to ask you, do you have the recommended parameter value for the test object I use?