3D radiometry
Methods and a computer program product for deriving temperature information with respect to surfaces within a scene that is imaged radiometrically. A time sequence of radiometric data is acquired in frames viewed from distinct angles. A three-dimensional structure of the scene is derived, allowing viewing angles and distances to the imaged surfaces to be inferred. Normalized surface areas of the imaged surfaces are calculated based on the inferred viewing angles and emissivities of the imaged surfaces are corrected accordingly. Corrections also account for background radiation impinging on the imaged surfaces. The radiometric data are converted to a perceptible temperature map of the imaged surfaces.
1. A method for deriving temperature information with respect to surfaces imaged radiometrically by means of a radiometric camera in motion with respect to the imaged surfaces, the method comprising:
a. acquiring and storing a time sequence of frames of radiometric data including a plurality of radiometric images from distinct angles of a scene containing the surfaces;
b. modeling a 3D structure of the scene;
c. inferring viewing angles and distances to the imaged surfaces based on the modeled 3D structure;
d. calculating normalized surface areas of the imaged surfaces based on the inferred viewing angles;
e. correcting emissivities of the imaged surfaces based on the inferred viewing angles; and
f. converting the radiometric data to a perceptible temperature map of the imaged surfaces.
2. A method in accordance with claim 1 , wherein modeling the 3D structure of the scene is performed using optical flow analysis.
3. A method in accordance with claim 1 , wherein acquiring is performed by means of an infrared radiometric camera.
4. A method in accordance with claim 1 , further comprising correcting the radiometric data to account for background radiation impinging upon the imaged surfaces.
5. A method in accordance with claim 1 , wherein the acquiring and storing are performed by means of a camera disposed on a vehicle traversing the imaged surfaces at street level.
6. A method in accordance with claim 1 , further comprising a step of calibrating an infrared camera in order to acquire the radiometric data.
7. A computer program product for deriving temperature information with respect to surfaces imaged radiometrically by means of a camera in motion with respect to the imaged surfaces, the computer program product comprising a non-transitory computer usable medium having computer readable program code thereon, the computer readable program code including:
a. a computer code module for storing a time sequence of images of the surfaces at a plurality of positions;
b. a computer code module for modeling a 3D structure of the scene;
c. a computer code module for inferring viewing angles and distances to the imaged surfaces based on the modeled 3D structure; d. a computer code module for calculating normalized surface areas of the imaged surfaces based on the inferred viewing angles;
e. a computer code module for correcting emissivities of the imaged surfaces based on the inferred viewing angles; and f. a computer code module for converting the radiometric data to a perceptible temperature map of the imaged surfaces.
8. A computer program product in accordance with claim 7 , wherein the computer code module for modeling the 3D structure of the scene is based upon optical flow analysis of the plurality of radiometric images.