TABLE 1. Guidelines Followed During Acquisition of Aerial Photographs.

Tidal Stage

Photography was acquired at low tide, +/- 0-1.5 ft., as predicted by the National Ocean Survey tables.

Plant Growth

Imagery was acquired when growth stages ensured maximum delineation of SAV, and when phenologic stage overlap was greatest.

Sun Angle

Photography was acquired when surface reflection from sun glint did not cover more than 30 percent of frame. Sun angle was generally between 20° and 40° to minimize water surface glitter. At least 60 percent line overlap and 20 percent side lap was used to minimize image degradation due to sun glint.

Turbidity

Photography was acquired when clarity of water ensured complete delineation of grass beds. This was visually determined from the airplane to insure that SAV could be seen by the observer.

Wind

Photography was acquired during periods of no or low wind. Off-shore winds were preferred over on-shore winds when wind conditions could not be avoided.

Atmospherics

Photography was acquired during periods of no or low haze and/or clouds below aircraft. There could be no more than scattered or thin broken clouds, or thin overcast above aircraft, to ensure maximum SAV to bottom contrast.

Sensor Operation

Photography was acquired in the vertical mode with less than 5° tilt. Scale/altitude/film/focal length combination permitted resolution and identification of one square meter area of SAV (at the surface).

Plotting

Each flight line included sufficient identifiable land area to assure accurate plotting of grass beds.

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