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How to use the digital photo point count system. PowerPoint PPT Presentation

Point Count System for Measuring Ground Cover from Digital Photos. Edward B. Rayburn West Virginia University 1078 Ag. Science Morgantown, WV 26506 304-293-6131-4209 erayburn@wvu.edu. How to use the digital photo point count system. Take digital photos of the pasture or hay field.

How to use the digital photo point count system.

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

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.