单相机实现地面已知尺寸物体真实坐标计算可行性咨询

You do not need a dual camera setup—a single camera is fully capable of solving this task given your constraints. Here's why and how:

Key Constraints That Enable Single-Camera Solution #

Your setup provides critical information that eliminates the need for stereo vision:

• Known camera height (2.5m above ground)
• Known real-world dimensions of the 3 objects
• Access to the objects' image coordinates

Step-by-Step Approach #

1. Camera Calibration
   First, perform standard camera calibration to obtain intrinsic parameters: focal length (fx, fy), principal point (cx, cy), and distortion coefficients. This corrects for lens distortion and sensor-specific quirks—skipping this is likely why your earlier focal-length-only attempt was inaccurate.

2. Define Your World Coordinate System
   Set the ground plane as the Z=0 plane. Position your camera at a known 3D coordinate (e.g., (0, 0, 2.5) if it's directly above the origin of your 10×3m area). Adjust this if your camera is offset from the area's center.

3. Calculate Real-World Coordinates
   Use the perspective projection equation to map image points to ground-plane coordinates:

   [u; v; 1] = K * [R | t] * [X; Y; 0; 1]
   

   • K: Intrinsic matrix from calibration
   • R: Rotation matrix (accounts for camera tilt/rotation relative to the ground)
   • t: Translation vector (camera's 3D position in your world system)
   • (X,Y): Real-world coordinates of the object point you're solving for

   Since you know the object's real dimensions, you can use two distinct image points from the same object (e.g., opposite corners) to solve for the scale factor and derive X and Y directly. For a perfectly top-down camera (no tilt), this simplifies to basic similar-triangle calculations using the object's known size and its pixel size in the image.

When Would You Need Dual Cameras? #

Stereo vision is only necessary if you lack critical information like:

• Unknown object dimensions
• Unknown camera position/height
• Need to calculate 3D coordinates for objects not on a flat plane

In your case, all required variables are known, so a single camera is more than sufficient.

内容的提问来源于stack exchange，提问作者Maximarina VI