The spectral reflectance properties of plants have been known for many years. In the late 1960s and early 1970s the idea of ratioing multiple bands of the visible and near infrared spectrum was proposed. The ratioing of bands tends to eliminate albedo effects and shadows. The resulting imagery and associated numerical data is generally known as "vegetation index". Several indexes have been developed in the last twenty years.
The Dycam ADC software supports the IPVI, NDVI and SAVI. Traditionally, near-infrared imagery has been difficult and expensive. An aerial infrared image alone is insufficient for band ratioing. A visible light image filtered for the correct band is also required. Satellite imagery has been available now for many years, but the cost is prohibitive for the small farmer and the ground resolutions are too low for "precision farming" needs.
The ADC is a portable digital camera specifically tailored for multi-band photography in the visible red and near-infrared. The camera and software allow calibration for the ambient conditions and apply the calibration value to all images made under the calibrated conditions. The 24-bit "color" image from the camera is evaluated by the host software as one of the three supported vegetation indexes. The processed "VI" image directly represents the result of the index equation used on a pixel-by-pixel basis. The resulting 8-bit image can be palletized, saved and exported for use with other software. The camera is easy to operate, rugged and compact.
The host software operates under Windows and DOS. The ADC model connects directly to the serial port and requires no additional boards in the computer. A serial cable, battery charger, filters and software are included.
Basic Specifications:
Spectral sensitivity: 600 nm to 1100 nm, Visible red and NIR ( TM bands 3 and 4 extended)
496 x 365 Pixels
24 bit color, 8 bits per band
Interface: RS-232 Serial
Image Storage: 8 to 24 (user selectable), 36 to 100 (available option)
Size: 6.7" x 3.2" x 1.2"
Weight: 10 oz.
Power: Rechargeable Ni-Cad or external 12VDC
Optics: 8.5 mm F4.5 in focus 1m to infinity
Exposure time: Automatic, 1/2000 sec to 2 sec or user selectable.
Triggering: On camera button or remote with interface connector.
Software: Windows application allows camera configuration, access and all file operations.
Indexes Supported: NDVI, SAVI and IPVI.
Calibration: User executes calibration routine on sample image made under ambient conditions.
File Types Supported: All common file types, .BMP, .TIF, .JPG, Targa etc.
