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Digital Photo Point Count System for Accurate Ground Cover Measurement

This guide outlines a systematic method for measuring ground cover using digital photographs. Begin by capturing images of your pasture or hay field and importing them into PowerPoint. Overlay the point count grid and identify the species or components at each grid point. Tabulate your findings, ensuring multiple counts for accuracy. For confidence intervals, a sample size of 100 points yields ±13% CI, while 250 points provide ±8% CI at a 50% frequency. Enhancing photo count accuracy by using 100-point samples improves ground cover calibration against dry matter yield.

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Digital Photo Point Count System for Accurate Ground Cover Measurement

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  1. Point Count System for Measuring Ground Cover from Digital Photos.Edward B. RayburnWest Virginia University1078 Ag. ScienceMorgantown, WV 26506304-293-6131-4209erayburn@wvu.edu

  2. How to use the digital photo point count system. • Take digital photos of the pasture or hay field. • Import photos into PowerPoint as a picture. • Copy the point count grid onto the slide. • Identify the species, botanical component or bare ground at the tip of each “V” and tabulate the numbers. • Relocate the grid and count again. • For 100 points the CI is ± 13% (0.05 probability) at 50% frequency. • For 250 points the CI is ± 8% (0.05 probability) at 50% frequency. • More photos using 100 points/photo is probably better than taking more than 100 points on a photo. • Clip some areas and hand separate the sample (quadrates in these photos) when calibrating percent ground cover against percent dry matter yield. • The effect of sample size on the confidence interval of a mean for a normal distribution (as in measurement of yield) and a binomial distribution (as in measurement of percent) are presented below.

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