Assessing the chromatic contrast in open surface excavations: a comparative study between subjective and quantitative approaches

The difficulties in the quantification of various aspects of visual impacts, among them the colour contrast, have resulted in delay of the development of effective assessment methodologies for mining operations. Technological evolution in image analysis has boosted the progression of more quantitative approaches. Yet, the critical question on how close the quantitative results are to the perceived colour difference remains an open issue. This paper is one of the few efforts to bridge subjective opinions gathered by a public preference survey with quantitative estimates of three different measurement approaches. Two main conclusions are drawn. First, people tend to compare the colour of the exposed excavation with the colour of the area near the edges of the quarry site. Second, the subjective colour difference is affected by landscape features that cannot be measured in numerical terms from existing image analysis tools.