METER Legacy Canopy Measurement Sensors

Rugged radiometer measures NDVI or PRI

• Measure NDVI or PRI vegetation indices at the plot or plant stand scale
• Non-destructive sampling of canopy greenup, senescence and plant stress
• Collect vegetation index data unattended for days, months or years
• Use low cost, research grade sensors to maximize spatial coverage
• Improve crop growth models with spatially explicit data
• Monitor data remotely from office or phone

Low cost, weatherproof radiometer

The SRS 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.

Deploy for months or even years

Most spectrometers are delicate and expensive, making long-term field deployment risky. The SRS is built for long-term exposure to the elements. Key design features:

• encased in durable Geloy housing
• epoxy-filled, watertight, and weatherproof
• fully sealed optics

These materials and methods have been tested over months and years on other buried and above ground sensors. Combined, these features help minimize drift in calibration over time.

Field ready and radiometrically calibrated

Each sensor is radiometrically calibrated to a NIST-traceable standard. Readings are output in units of radiant flux density. Calibration information is stored on board the sensor so you never have to worry about keeping track of calibration coefficients.

Continuously monitor NDVI, PRI at the plot scale

NDVI and PRI are calculated from measurements of of electromagnetic radiation reflected from canopy surfaces. They are correlated with canopy variables such as:

• light use efficiency (LUE)
• biomass and crop yield
• crop and forest phenology
• canopy growth
• photosynthetic performance/CO_² uptake

SRS sensors measure incident or reflected radiation in two bands:

• Normalized Difference Vegetation Index (NDVI) bands are centered at 650 nm and 810 nm with 50 nm and 40 nm full width half maximum (FWHM), respectively.
• Photochemical Reflectance Index (PRI) bands are centered at 532 nm and 570 nm with 10 nm FWHM.

Hemispherical or directional field of view

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 36°. 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

Low cost for maximum spatial coverage

By focusing on just two bands, it’s possible to make an accurate multiband radiometer for a fraction of what a full-feature spectroradiometer costs. Use the SRS-NDVI and SRS-PRI sensors to maximize spatial coverage and explore spatial and temporal variability in canopy structure and function.

Data logging and software

The SRS is an SDI-12 digital sensor.

When used with METER’s EM50 series data loggers, the SRS plugs in via stereo connector. Setup is straightforward: select the sensor type from a drop-down menu, set the measurement interval and start logging data. No programming necessary.

The SRS provides readout of the individual bands in W m^-2 nm^-1 or W m^-2 nm^-1 sr^-1, depending on sensor type. Decagon’s DataTrac 3 database and graphing software can manage your data set and will calculate NDVI or PRI automatically.

The SRS sensor is also compatible with Campbell Scientific and other SDI-12 capable data loggers.

Collect data and monitor remotely

When used with METER’s EM50G data loggers, you can monitor remote sites from your office, phone, or any internet-connected device. Observe field conditions, check sensor and system function, or download data from sites that are difficult to access.

• SRS manual
• SRS firmware updater
• SRS NDVI integration guide
• SRS PRI integration guide
• SRS quick start
• SRS CSI data logger example program

The D1 Dendrometer is a simple tool that allows you to manually measure changes in the circumference of tree stems over time. The D1 is designed to be installed, left in place, and periodically visited to record changes in the circumference resulting from tree or stem growth.

The D1 is made by German manufacturer METER Ag with painstaking attention to detail. The D1’s measuring tape is made of low-friction, low thermal expansion Astralon plastic. It wraps around the trunk of a tree and fastens with a spring mechanism that allows the tape to expand as the tree grows. The researcher measures the change in diameter, typically at longer intervals (once a year). The measurement scale is in units of π so there is no need to convert circumference to diameter.

The D1 has a specially shaped frictionless Vernier scale to make it easier to take a precise reading. UMS has additionally reduced friction by manufacturing the eyelets without burrs and eliminating printing on the bark-side surface of the tape.

The D1 measures trees with diameters from 10 to 66 cm. Two tapes can be connected to measure larger trunks. Stems less than 40 cm in diameter should use the short spring, and the longer spring should be used on stems > 40 cm in diameter.

• D1 Dendrometer manual

The D6 is an automated, weatherproof sensor that provides continuous high-resolution measurements of tree or branch circumference. It is designed to be attached to tree boles or branches and logged continuously for long term data collection.

Expands as the tree grows

A broad measurement range means that it can be left attached to most trees without ever having to make adjustments.

Sensitive to small diameter changes

You can use the D6 to monitor diurnal fluctuations in stem circumference related to water transport from the roots to the leaves. You can also monitor immediate response to weather events. When used over longer time periods, the D6 can also be used to monitor tree growth.

Designed to protect tree tissue

The D6 mounts without screws or hardware that penetrate tree tissue. It is a small, lightweight sensor that does not damage bark or disturb tree growth. A flexible Teflon buffer layer minimizes friction and prevents wounding.

Weatherproof

The measuring cable is made of INVAR steel which is highly resistant to corrosion and has low temperature dependence (<1 µm/mK). Strain gages are covered with rubber polymer.

Adjustable

The pad and cable can be configured to fit any tree circumference.

Data logging

We recommend using Campbell Scientific data loggers for powering and logging the D6.

• D6 Dendrometer manual

The infrared thermometer monitors surface temperature by measuring the thermal energy radiated from any surface within its field of view.

Highly accurate, meticulously calibrated

Has an accuracy of ± 0.2 °C when the target temperature is within 20 °C of the sensor body temperature. The IR Thermometer is calibrated from -30 to 65 °C.

Non-contact, continuous monitoring

Delivers a continuous stream of temperature data from the entire field of view, not just data from a single leaf.

Purpose built for plant science applications

Not a generic IR thermometer, but a scientific-grade sensor designed for making canopy measurements. It comes with a highly accurate factory calibration. A radiation shield and mounting bracket are included.

Four field of view options

Select the right field of view for your application. Choose a circular aperture with a half angles of 14, 18, or 22 degrees, or pick a horizontal aperture with 13 degree vertical half angle and 32 degree horizontal half angle.

Corrects for sensor temperature

Measures both the target temperature and the temperature of the sensor itself to correct for the temperature sensitivity of the detector.

Rugged, lightweight, weatherproof

Tough germanium window makes the sensor durable without decreasing its accuracy. A weatherproof aluminum body withstands harsh weather conditions.

Monitor temperature from your mobile device

Compatible with METER’s simple, low-power EM50 series data loggers. Run the sensor and logger on five AA batteries. Download data in your office or anywhere with an internet connection. No programming required.

Applications

• Stomatal conductance: Monitor water use in real time by using a biophysical model to back-calculate stomatal conductance
• Plant water stress
• Evapotranspiration: Use temperature to estimate stomatal conductance instead of using a crop coefficient
• Calculate true Vapor Pressure Deficit (VPD): Reduce errors when modeling by using actual canopy temperature instead of air temperature

• Infrared Thermometer manual