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Using Aerial Photos for Nutrient Management Planning

Figure 3.2.1 A partial acreage grid map

Calculating Distances

The scale of an aerial photo is the ratio of the distance between two objects on a photo to the actual distance on the surface of Earth, in the same units. For example, an aerial photo with a scale of 1:5,000, a 1 cm measurement on the photo is equal to 5,000 cm or 50 m on the actual ground. Distance can be calculated from the scale of a photo using the following equation:

Distance on the Ground (units) = Measurement on Photo (units) x Scale of Photo (e.g., 5,000)

Calculating Distances from an Aerial Photo

AOPA does not allow surface application and incorporation of manure within 30 m of a common body of water.

A producer has a field that is bordered by a creek. Using an aerial photo, the producer wants to determine the width of the grassed strip between the edge of the field and the creek. He wants to determine if he can apply manure right to the edge of this field or if he needs to stay back from the grassed edge to meet the 30 m setback. On a 1:5,000 scale aerial photo, the distance between the edge of the field and the creek is 1.4 cm. Distance on the Ground (units) =

Measurement on Photo (units) x Scale of Photo (e.g., 5,000)

= 1.4 cm x 5,000 = 7,000 cm

= 70 m is the distance on the ground The edge of the field is 70 m from the creek. Therefore, the producer can apply manure to the field boundary, provided it is incorporated within 48 hours of application.

Estimating Areas

To estimate areas on aerial photos of known scale the following materials are needed:

standardized grid that is printed or copied onto a •

transparency fine tipped, non-permanent pen (for use on •

transparencies) standard school geometry set • calculator •