Submitted to: Environmental Monitoring and Assessment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2005
Publication Date: 12/5/2006
Citation: Booth, D.T., Cox, S.E., Berryman, R.D. 2006. Point sampling digital imagery with 'samplepoint'. Environmental Monitoring and Assessment 123:97-108. Interpretive Summary: Taking a digital picture is much easier, quicker, and less expensive than conventional methods for measuring percent occurrence of objects like bare ground, weeds, or plant cover. However, measurement accuracy from digital pictures has not equaled that from conventional field measurements. We created a new software program, ‘SamplePoint,’ to make quick, accurate measurements from digital images and tested it for accuracy and speed. We found SamplePoint data accuracy was comparable to that from the most accurate field-methods for ground-cover measurements and that its ease of use allowed data to be obtained in less than half the time required by a previous method for obtaining data from digital pictures. We recommend SamplePoint for making measurements of percent occurrence from digital images or for calibrating more complicated software programs that automatically extract measurements.
Technical Abstract: Measuring percent occurrence of objects from digital images can save time and expense relative to conventional field measurement; however, accuracy of image analysis has not reached the level of the best conventional field measurements. Additionally, most image-analysis software programs are very technical and require advanced user training to successfully analyze images. Here we present a new software program, ‘SamplePoint,’ that provides the user a single-pixel sample point and the ability to view and identify the pixel context. We found SamplePoint to allow accuracy comparable with the most accurate field-methods for ground-cover measurements, and ease of use that allows rapid measurements from image data. We recommend SamplePoint for calibrating the threshold-detection level of image-analysis software or for making measurements of percent occurrence from digital images.