Camera calibration and distance measurement based on homography

An apparatus for estimating a real world height in an image, comprising:

• one or more memories;
• and
• one or more processors coupled with the one or more memories, wherein the one or more processors are configured, individually or in combination, to:
• obtain a first image and a second image from a camera installed at an unknown height in an environment, wherein the first image includes a first object at a first location in the environment and the second image includes the first object at a second location in the environment, and wherein the first object has a known object height;
• determine, based on the known object height, a first vector that intersects with a point on the first object in the first image and points to a real world ground plane, wherein the point on the first object has a known point height based on the known object height;
• determine, based on the known object height, a second vector that intersects with the point on the first object in the second image and points to the real world ground plane;
• and
• calibrate the camera by determining a height of the center of a camera lens of the camera using an intersection of the first vector and the second vector.

A non-transitory computer-readable medium storing instructions for estimating a real world height in an image, wherein the instructions are executable by one or more processors to:

• obtain a first image and a second image from a camera installed at an unknown height in an environment, wherein the first image includes a first object at a first location in the environment and the second image includes the first object at a second location in the environment, and wherein the first object has a known object height;
• determine, based on the known object height, a first vector that intersects with a point on the first object in the first image and points to a real world ground plane, wherein the point on the first object has a known point height based on the known object height;
• determine, based on the known object height, a second vector that intersects with the point on the first object in the second image and points to the real world ground plane;
• and
• calibrate the camera by determining a height of the center of a camera lens of the camera using an intersection of the first vector and the second vector.