IMAGE ANALYSIS OF WATER–SENSITIVE CARDS FOR SPRAY COVERAGE EXPERIMENTS

Water–sensitive papers can be useful spray droplet sampling devices provided that their limitations are taken into account. One of these limitations is that the color of the unstained areas on a water–sensitive paper changes as the distance between stains decreases. An image analysis system and an appropriate image thresholding calibration procedure were developed. Ideally, the calibration is performed for each consistent set of samples. One useful feature of the calibration procedure is the estimation of the absolute error in the measurement of the percent area covered. In the example used to describe the method, the absolute error in percent area covered was estimated to
3.5%.