Page 88 - Nutrient Management Planning Guide

83

Chapter 3.2

By overlaying a transparent acreage grid map on an aerial photo you can estimate area, knowing the aerial photo’s scale. The following is a list of steps to estimate areas from aerial photos:

Trace the outline of areas to be estimated on a 1.

photocopy of the aerial photo, a printed copy of a digital image or an unmarked transparency. This will make area boundaries easier to identify and will preserve the original photo.

Superimpose the standardized grid on the tracing 2.

of the aerial photo and trace directly on the grid the boundaries of all areas to be estimated. Put the grid on a white background for easier 3.

viewing. Count and record the grid dots contained in each outlined area. For dots that lie on the boundary line, count every other one. Using the grid dots recorded in step 3 and table 3.2.4 4.

or table 3.2.5 to estimate areas identified in the aerial photo.

Calculating Area from an Aerial Photo

Based on the aerial photo of this field (1:5,000 scale), determine the number of hectares eligible to receive manure (taking into account required and voluntary setbacks from sensitive areas, obstructions, non-productive areas, etc.).

Total number of grid dots in areas with field boundary = 1,440

Total number of dots in shaded areas (i.e., setbacks, physical obstacles) = 38

Referring to table 3.2.4, at the 1:5,000 scale, each grid dot is equal to 0.0252 ha.

Total field area (ha) = number of grid dots x ha per grid dot = 1,440 x 0.0252

= 36.3 ha is the total field area which included 1,440 grid dots

Total shaded areas (e.g., setback, obstacles) (ha) = number of grid dots x ha per grid dot = 38 x 0.0252

= 1.0 ha is the total field area which included 38 grid dots

Approximate area available for manure (ha) = Total field area (ha) - Total shaded area (ha) = 36.3 x 1.0

= 35.3 ha of this field is available for manure application

tip

To estimate the area eligible for manure application, trace the outline of fields manure is to be applied, and then outline and fill in any areas ineligible to receive manure (e.g., application setbacks, sensitive areas).