Feature evaluation for target/background discrimination in image sequences taken by approaching sensors

Abstract

The conspicuity of different targets in image sequences taken by approaching sensors is addressed in applications such as the assessment of camouflage effectiveness or the performance evaluation of autonomous systems. In such evaluation processes the consideration of background characteristics is essential due to the propensity to confuse target and background signatures. Several discriminating features of target and background signature can be derived. Furthermore, the changing aspect and spatial resolution during an approach on a target have to be taken into account. Considering salient points in image sequences, we perform a nominal/actual value comparison by evaluating the receiver operating characteristic (ROC) curve for the detections in each image. Hence, reference regions for targets and backgrounds are provided for the entire image sequence by means of robust image registration. The consideration of the uncertainty for the temporal progression of the ROC curve enables hypothesis testing for well-founded statements about the significance of the determined distinctiveness of targets with respect to their background. The approach is neither restricted to images taken by IR sensors nor applicable to low level image analysis steps only, but can be considered as a general method for the assessment of feature evaluation and target distinctiveness. The analysis method proposed facilitates an objective comparison of object appearance with both, its relevant background and other targets, using different image analysis features. The feasibility and the usefulness of the approach are demonstrated with real data recorded with a FLIR sensor during a field trial on a bare and mock-up target

Search by photo methodology for signature properties assessment by human observers

“…Furthermore, we believe the observer trial methodology can be cost-effective compared to other tests of signature properties such as image sequences at different target distances (requires helicopter [13]) or transportation of a large number of soldiers for signature testing in the field (several different locations, at different seasons), but still reliable and easy to use. As an example the methodology allows signature solutions intended for winter and summer to be tested simultaneously, and is therefore quick.…”

“…In our methodology targets are recorded (e.g. photographed) in a natural setting, which commutes well with criteria such as detection time and probability of detection, but rules out detection range, even if the latter can be found well suited as ranking parameter in other test set-ups [13,18]. The choice of detection time over probability of detection is a decision we had to make ourselves, and our rationale was the following:…”

“…Photo-simulation by using human observers as an assessment method of camouflage effectiveness has been used in various forms in the recent decades [1][2][3][4]. Other methodologies have also been tested out, involving video surveillance [5], simulation of human vision [6][7][8][9][10][11], similarity measures of target-background by image analysis techniques [2,11], assessment by simulation of target vehicles against different backgrounds [12], and image sequences taken by approaching sensors [13].…”