Part I: Section B
Ground-Truth Monitoring
3.1 Platform Photography

The platform is manufactured using polyvinyl chloride (PVC) tubing on which a camera is mounted pointing vertically downward from a height of 5.5 feet. The camera is mounted on a bracket, attached to the 1-m 2 quadrat, to provide consistency. The 1-m 2 quadrat appears in the center of the photograph to provide an estimate of scale, allowing for the accurate measurement of vegetative cover in the photo. Photographs taken with this setting (using a 35mm camera with a 28mm focal length and 5.5 feet above the ground) have a pixel size of 1mm² and show grazed leaf-tips on grass, bird footprints, goose droppings, weeds, and grass cover and vigor (Figure IB-1). Depending on the camera specifications, the height of the camera above the ground can be adjusted to capture a 1m² area. At one side of the frame, a clipboard is attached to provide a surface for displaying the date, field identification, and location within the field (Figure IB-2). For a more complete description on how to construct a platform photograpy system refer to Part III, Section B of the manual.

Figure IB-1: Platform photography. A 35-mm camera mounted on a lightweight platform of polyvinyl chloride tubing used to monitor goose grazing.

Figure IB-2: A clipboard attached to one side of the frame provides a surface for displaying the date, field identification, and location within the field (e.g., exclosure #8 inside).

Images taken using the platform allow for accurate determination of vegetative cover (Figure IB-3). Accurate measurement of vegetative cover is useful in determining the intensity of goose grazing.

Figure IB-3: Color photographs of a 1m 2 have been converted to a Boolean image for analysis of grass cover. Green (living) leaves were classified and displayed as black. Non-green litter and soil were classified and shown as white. Pixels were counted to determine percent of green leaves and soil/litter.


If platform photography is not used, monitoring can be conducted using a hand-held camera. However, in order to synchronize the GPS location to the picture, the camera should have a clock (time-stamp) feature. Although hand-held photographs can be adequate, platform photography is recommended.

We have used Kodak ® Color Royal Gold - Speed 400 film, which has produced high-quality pictures. Use 36-exposure film to match the form used for collecting ground-truth data (37 rows per form).

<< previous page  
1. Introduction
2. Purpose
3. Equipment Needed
- 3.1 Platform Photography
- 3.2 Hand-held GPS Unit
4. Methods/Instructions
5. Forms Needed
6. Costs
7. Appendices
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