The SRS-NDVI is a matchbox-sized, multiband radiometer that can be mounted on a fence post, tripod, or meteorological tower. It’s inexpensive enough to deploy multiple sensors simultaneously. And it’s rugged enough to leave in the field for an entire growing season, or longer. Combined with the S-Node, it makes an ideal LoRaWAN remote NDVI monitoring station.
NDVI and PRI are calculated as the ratio between reflected and incident radiation, measured using downlooking and uplooking sensors, respectively. Depending on ambient sky conditions, one uplooking sensor may be able to provide reference values for multiple downlooking sensors.
Uplooking SRS sensors have a hemispherical view with Teflon diffusers providing a cosine corrected response. They should be mounted above the canopy with an unobstructed view of the sky.
Downlooking sensors are equipped with field stops that restrict the field of view of the SRS to 20°. The field stops allow you to aim the sensor at a specific target and exclude non-canopy elements, such as a tower infrastructure, from the field of view. The sensor can be mounted to monitor single plants, row crops, plots, or forest stands. Mounting height will determine the measurement area. The measurement spot size at a nadir view angle is 0.35*height above canopy.
Sensors are typically mounted above the canopy using a pole, post, tripod, or tower depending on the height of the canopy. Small size, low weight, and durable construction make the SRS suitable for attaching to a mobile sampling platform. They can also be attached to a mobile platform.
|NDVI wavebands||630 ± 5 and 800 ± 5 nm peak wavelengths, with 50 nm and 40 nm full width half maximum (FWHM) band widths|
|PRI wavebands||530 ± 3 and 570 ± 3 nm peak wavelengths, with 10 nm full width half maximum (FWHM) band widths|
|Foreoptics||(1) Cosine correcting Teflon diffuser, hemispherical field of view
(2) Field stop, 20° field of view
|Calibration||NIST traceable calibration to known spectral irradiance (W m-2 nm-1) or radiance (W m-2 nm-1 sr-1)|
|Accuracy||10% or better for spectral irradiance and radiance values|
|Measurement Time||< 300 ms|
|Dimensions||43 x 40 x 27mm|
|Weight||Sensor: 47g Sensor with 5 m cable: 170 g|
|Power Requirements||3.6 to 15 VDC, 4 mA (reading, 300 ms), 30µA (quiescent)|
|Operating Temperature Range||-40 to 50°C|
|Cable Length||5 m standard, custom cable length available upon request|
|Connector type||3.5 mm (stereo) plug or stripped and tinned lead wires (pigtail)|