If you replace a camera or remove the cameras from the bar and attach them elsewhere, this page explains how to do the initial extrinsic camera calibration.

Step 1: Find Calibration Scene

A good calibration scene has texture and some objects far away, ideally at several hundred meters to kilometer range. We typically point the stereo camera from our office roof on the 5th-floor building out to the city. The building and tree structures are feature-rich, and Google Earth makes it easy to measure distances to faraway objects.

Here we are on the roof with a NDR-HDK-2.0-50-65-A stereo camera. This is our normal setup for extrinsic camera calibration. We mount the stereo camera on a tripod and point it toward the city. For long-range cameras (30-deg HFOV), we point the camera more horizontally to see buildings up to 1 km away.

The output of a well calibrated camera should look like this (pointed from our roof to the parking lot below for a 65-deg camera):

Notice that the depth map is filled in (lower left window). For longer ranges, we point the camera more horizontally so that we can see buildings at longer distances (180 m and 1 km buildings, as measured using Google Earth). The following image is for 135-deg cameras with 1-m baseline:

Here is another scene that will work for calibration. The building on the left-hand side is at 160 meters. For 30-deg systems, you'll want an object farther than that, typically at the maximum desired operating range.

Step 2: Install configuration files

Copy extrinsics.ini , intrinsics.ini, and master_config.ini to /home/nodar/.config/nodar/config

The extrinsics.ini should be set to the following initial values for the 1-m HDK:

phi = 0
theta = 0
psi = 0
T1 = 1
T2 = 0
T3 = 0

phi, theta, and psi are relative pitch, yaw, and roll, respectively. And (T1, T2, T3) is the translation vector between the cameras. Roughly speaking, T1 is along the bar (left-right), T2 is up-down, and T3 is along the line-of-sight of the camera.

The intrinsic camera parameters in intrinsics.ini are measured at NODAR HQ using an Image Engineering GEOCAL. These are fixed values.

The master_config.ini must be updated with the right camera serial numbers. For example,

camera_left_id = 250500957
camera_right_id = 245002384