# US 12,762,745 B2 · Camera calibration and distance measurement based on homography > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,762,745 B2 - Document ID: US12762745B2 - Status: Granted - Kind: B2 - Application number: 19/098,715 - Filed: 2025-04-02 - Published: 2025-07-17 - Granted: 2026-10-13 - Earliest claimed: 2022-11-23 - Assignees: Tyco Fire & Security GmbH - Applicants: Tyco Fire & Security GmbH - Inventors: Amit Rozner; Yohay Falik; Calanit Dotan - Web page: https://patentgrep.com/patent/US12762745B2 ## CPC - G06T 7/80: Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration - G06T 7/60: Analysis of geometric attributes - G06T 7/73: using feature-based methods - H04N 17/002: {for television cameras} - G06T 2207/30201: Face - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract Example implementations include a method, apparatus and computer-readable medium for estimating a real world height in an image, comprising obtaining 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 of known height at a first location and the second image includes the first object at a second location; determining, 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; determining, 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 determining a height of the center of a camera lens of the camera using an intersection of the first and second vector. ## Claims ### Claim 1 A method for estimating a real world height in an image, comprising: obtaining 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; determining, 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; determining, 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 calibrating 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. ### Claim 2 (depends on 1) The method of claim 1, wherein the point is a second point, further comprising: estimating, using a homography matrix that transforms an image plane associated with the image to a real world plane, a first position of a first point on the first object in the first image based on the real world ground plane; estimating, using the homography matrix, a second position of the first point on the first object in the second image based on the real world ground plane. ### Claim 3 (depends on 2) The method of claim 2, wherein the first point is associated with a base of the first object, and the second point is associated with a top of the first object. ### Claim 4 (depends on 2) The method of claim 2, wherein the first object is a person, the first point is associated with a foot of the person, and the second point is associated with a head of the person. ### Claim 5 (depends on 1) The method of claim 1, further comprising: obtaining a third image from the camera, wherein the third image includes a second object without a known height in the environment; and determining a height metric of the second object using a homography matrix and the height of the center of the camera lens. ### Claim 6 (depends on 5) The method of claim 5, wherein determining the height metric of the second object comprises: estimating, using the homography matrix, a third position of a third point on the second object based on the real world ground plane; determining, based on the height of the center of the camera lens, a third vector that intersects with a fourth point on the second object and points to the real world ground plane; and determining the height metric between the third point and the fourth point on the second object based on a distance between the third point and the fourth point relative to the height of the center of the camera lens. ### Claim 7 (depends on 6) The method of claim 6, wherein the third point is associated with a base of the second object, and the fourth point is associated with a top of the second object. ### Claim 8 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. ### Claim 9 (depends on 8) The apparatus of claim 8, wherein the point is a second point, and wherein the one or more processors are further configured to: estimate, using a homography matrix that transforms an image plane associated with the image to a real world plane, a first position of a first point on the first object in the first image based on the real world ground plane; estimate, using the homography matrix, a second position of the first point on the first object in the second image based on the real world ground plane. ### Claim 10 (depends on 9) The apparatus of claim 9, wherein the first point is associated with a base of the first object, and the second point is associated with a top of the first object. ### Claim 11 (depends on 9) The apparatus of claim 9, wherein the first object is a person, the first point is associated with a foot of the person, and the second point is associated with a head of the person. ### Claim 12 (depends on 8) The apparatus of claim 8, wherein the one or more processors are further configured to: obtain a third image from the camera, wherein the third image includes a second object without a known height in the environment; and determine a height metric of the second object using a homography matrix and the height of the center of the camera lens. ### Claim 13 (depends on 12) The apparatus of claim 12, wherein to determine the height metric of the second object comprises to: estimate, using the homography matrix, a third position of a third point on the second object based on the real world ground plane; determine, based on the height of the center of the camera lens, a third vector that intersects with a fourth point on the second object and points to the real world ground plane; and determine the height metric between the third point and the fourth point on the second object based on a distance between the third point and the fourth point relative to the height of the center of the camera lens. ### Claim 14 (depends on 13) The apparatus of claim 13, wherein the third point is associated with a base of the second object, and the fourth point is associated with a top of the second object. ### Claim 15 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. ### Claim 16 (depends on 15) The non-transitory computer-readable medium of claim 15, wherein the point is a second point, further comprising instructions executable by the one or more processors to: estimate, using a homography matrix that transforms an image plane associated with the image to a real world plane, a first position of a first point on the first object in the first image based on the real world ground plane; estimate, using the homography matrix, a second position of the first point on the first object in the second image based on the real world ground plane. ### Claim 17 (depends on 16) The non-transitory computer-readable medium of claim 16, wherein the first point is associated with a base of the first object, and the second point is associated with a top of the first object.