Search by photo methodology for signature properties assessment by human observers

Abstract

Reliable, low-cost and simple methods for assessment of signature properties for military purposes are very important. In this paper we present such an approach that uses human observers in a search by photo assessment of signature properties of generic test targets. The method was carried out by logging a large number of detection times of targets recorded in relevant terrain backgrounds. The detection times were harvested by using human observers searching for targets in scene images shown by a high definition pc screen. All targets were identically located in each "search image", allowing relative comparisons (and not just rank by order) of targets. To avoid biased detections, each observer only searched for one target per scene. Statistical analyses were carried out for the detection times data. Analysis of variance was chosen if detection times distribution associated with all targets satisfied normality, and non-parametric tests, such as Wilcoxon's rank test, if otherwise. The new methodology allows assessment of signature properties in a reproducible, rapid and reliable setting. Such assessments are very complex as they must sort out what is of relevance in a signature test, but not loose information of value. We believe that choosing detection times as the primary variable for a comparison of signature properties, allows a careful and necessary inspection of observer data as the variable is continuous rather than discrete. Our method thus stands in opposition to approaches based on detections by subsequent, stepwise reductions in distance to target, or based on probability of detection.

Review of camouflage assessment techniques

“…Camouflage is typically deployed to reduce the visual signature of targets, thereby maximizing the average time needed by an observer to find the target in the scene. Search time (e.g., [29][30][31]33,35,55,66]) and detection probability (e.g., [29,33,41,42,67]) are therefore often adopted as metrics to quantify the effectiveness of camouflage. Effective camouflage measures should result in an increase in search time and a decrease in detection probability.…”

“…Field search trials can in principle be replaced by experiments in the laboratory using either photographs and videos or computer simulated virtual environments [30,68]. The use of large panoramic scenes enables the investigation of the effects of FOV restrictions on human visual detection performance and search strategies ( [67,69]; see Figure 3 and Figure 4).…”

Spectral characteristics of moist birch leaves and synthetic materials: experimental studies and evaluation of models

“…According to known literature, several studies have been carried out assessing camouflage net effectiveness 11,12,[17][18][19][20] and camouflage textile effectiveness 3,5,6,8,[21][22][23][24] but mainly considering spectral reflectance (or pattern) background matching. Little has been reported on spectral transmission properties of camouflage materials as a function of both (i) the number of layers in a stack and (ii) wavelength.…”

Camouflage performance of winter uniforms: photosimulations in the visual spectrum

“…The methodology used to assess winter camouflage was based on photosimulations with observers [26,38,39]. We have recently used the method for similar tests, as reported in [12,[27][28][29]40]. For interested readers, we refer to these works for extensive details of the test methodology.…”

“…In recent years, FFI has developed a photosimulation methodology for evaluating the visual camouflage effectiveness of camouflages [12,[27][28][29][30] based on test methods used by other nations [26,[31][32][33][34][35]. The methodology requires soldiers to visually search for camouflage targets (uniforms) in various scenes, with detection time and probability of detection as metrics to quantify the camouflage effectiveness.…”