Passive Ranging
Abstract
This paper compares the classical photogrammetric approach to the passive ranging problem with the approach based on the theory of optical flow applied to dynamic imagery. It also describes various errors, due to the environment and imperfections of the sensor system, long recognized by photogrammetrists but largely ignored by proponents of the optical flow methodology. An error sensitivity analysis indicates that the optical flow approach is more sensitive to errors--and to those due to image distortion, in particular--than is the photogrammetric approach. This is primarily because of the necessarily small line-of-sight angle between two views of the same object point by the sensor, especially when the sensor platform is constrained to move nearly parallel to the optical axis of the system. Although this constraint on the platform motion guarantees that the focus of expansion (FOE) remains in the field of view, that fact does not make the system less sensitive to error, but rather more so. Analysis shows that the opposite constraint imposed by photogrammetrists, having the platform move in a direction orthogonal to the optical axis, reduces the error sensitivity even though it forces the FOE out of the field of view--in fact, to infinity.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1988
- Accession Number
- ADA206884
Entities
People
- Irwin W. Kay
Organizations
- Institute for Defense Analyses