DEEPIKA SAHU, Department of Soil Science and Agricultural Chemistry
ANJALI PATEL, Department of Agronomy
Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.)


The RapidSCAN CS-45 is a small, hand-held instrument that is composed of a polychromatic light source and three spectrally sensitive photo-detectors (670 nm, 730 nm and 780 nm) with an embedded microcontroller that coordinates data collection, geospatial location, data storage, in-situ configuration of an agronomic mathematical model and data transfer.
  • A modular software design approach facilitates configuring the sensor to accommodate user needs.
  • Application operating system (OS) modules have been developed for biomass predication, N rate recommendation, plant vigor assessment, and yield prediction using point and scan data collection.
  • New technologies like RapidSCAN CS-45 crop sensor and others can provide small and mid sized producers access to these precision agriculture tools.
  • Tools such as these can provide the small and midsized farmer with valuable information regarding crop nutrient and health status needed in order to make informed decisions regarding the management of their agricultural operation.
  • However, data produced by these instruments are generally in the form of simple vegetation indices and require post-processing of data in order to effect a calibration and/or deployment as a canopy diagnostic tool.
  • Users of these technologies have expressed the need for active optical sensor (AOS) instruments (Holland et al., 2012) to provide approximated data calibrated in agronomical units, for example, biomass in tons per hectare, kg N per hectare, approximate yield, leaf area index (LAI) units, etc. plus some basic statistical calculations pertaining to the crop canopy structure. To address this need, a new software ecosystem for the RapidSCAN CS-45 has been developed.
  • The sensor is unaffected by ambient illumination allowing it to take accurate biomass measurements day or night due to its internal polychromatic light source.
  • The sensor is capable of collecting data from vegetation at sensor-to-canopy distances ranging from 0.3 meters to over 3 meters. Information produced by the sensor includes NDVI/ NDRE vegetation indexes, latitude/longitude and sample statistics as well as basic reflectance information.

The RapidSCAN CS-45 is sensor is ergonomically designed for ease-of-use and is light in mass, nominally 0.7 kg.
  • The sensor is composed of a microcontroller that coordinates optical sensing data collection and storage, a power management controller that performs battery charging and monitoring as well as system voltage conversion, a GPS sensor for geospatial data location and a user interface (display and keypad).
  • The optical component of the RapidSCAN CS-45 has been pulled forward from Holland Scientific’s Crop Circle ACS-430 three-channel AOS.
  • The RapidSCAN simultaneously collects spectral reflectance data for the red (670nm), red-edge (730nm) and NIR (780nm) spectral bands.
  • The light source is a polychromatic lamp that simultaneously emits light in each of these spectral bands.
  • Detection is performed synchronously in accordance with light source modulation and measured irradiance values are converted to reflectance values spanning from 0 to 100%.
  • The NDVI and NDRE vegetation indices are computed from these reflectance values. Data are stored in a 32Mb nonvolatile memory.
  • The RapidSCAN CS-45 contains sufficient memory to store over 15,000 canopy scans (NDRE, NDVI and reflectance) including geospatial data and descriptive statistics for each scan.
  • The RapidSCAN’s GPS receiver utilizes a SiRFStar IV core with high sensitivity low noise amplifier (LNA); -160dB, tracking.
  • A ceramic patch antenna (RHCP) is connected to the GPS’s core’s LNA and provides ~5dBic of gain at zenith with a center frequency of 1581 MHz and a bandwidth of 15 MHz.
  • The GPS core has EGNOS, WAAS, GAGAN and MSAS capability embedded with correction of positional errors due to ionospheric and orbital disturbances.
  • Overall spatial accuracy is typically less than 2.0 meters. The RapidSCAN’s power source is a 4.2-volt lithium, polymer cell.
  • The cell can power the instrument for over 20 hrs of operation. A power management controller supervises cell charging and charge termination. Instrument recharging is performed using either a 5 -voltage USB wall charger or a USB port from an active (powered ON) PC USB port.
  • A typical charge cycle can last up to 5 hours depending on the discharge state of the lithium cell.

Figure 2. RapidSCAN CS-45 system block diagram

The RapidSCAN software application (app) ecosystem consists of seven software apps. These apps include: Point-and-Scan, N-Rec Split, NRec Dose, GeoLog, LAI Estimator, Yield Estimator and Biomass Estimator.
  • Each application is uploadable to the RapidSCAN using an app manager called RapidAPP. RapidAPP negotiates software transfer, configuration parameters and registration codes with the RapidSCAN sensor via a USB serial connection.
  • While all of these potential applications could potentially be integrated into one extensive app, multiple apps were designed so as to maintain ease-of-use by minimizing each app’s learning curve and by reducing the degree of complexity of the user interface.

  • Internal differential GPS for geolocating canopy measurements.
  • Polychromatic light source for sunlight independent measurements – scan day or night.
  • Three spectral bands (670 nm, 730 nm and 780 nm) for acquiring NDRE and NDVI measurements simultaneously.
  • Internal lithium ion battery for up to 40 hrs of operation between charges.
  • Ergonomic design for low fatigue ease-of-use.
  • Micro USB connector for retrieving data and charging sensor.
  • Integrated data logger for logging canopy re ectance, measurement statistics, GPS location and vegetation indexes.

  • Hail damage estimation
  • Nutrient and fertilizer studies
  • Herbicide performance studies
  • Plant biomass quantification
  • Trend/detect plant vigor changes
  • Early disease detection
  • Leaf senescence studies
  • Turf and agricultural landscape mapping
  • Hybrid selection


Sensor-to-Canopy Range: Typically 1.0ft (0.3 m) to >9.8 ft(>3 m)
Field-of-View: ~45 degrees by ~10 degrees;
Active Light Source: Modulated polychromatic lamp
Photo detection: Three channel silicon photo detector
Optical Measurement Bands: 670 nm, 730 nm and 780 nm

GPS Accuracy: <1 meter CEP 50, SBAS enabled
Operating Range: 0 to 50 ºC
Communication Interface: USB 2.0 transceiver
Serial Communication: 56000, no parity, 8 data bits,1 stop bit
Power: Internal lithium battery
Memory Storage: 3 M bytes (>25,000 data points with all logging features enabled)
Battery Life: Typically > 20 hrs

Enclosure: Plastic and powder-coated aluminum
Environmental: IP65 for dust and water resistance
Weight: 1.75 lb (0.8 kg)
Dimensions: Width 4.0 in (10.2 cm), Length 8.9 in (22.6 cm), Height 6.75 in (17.1 cm)
Serial/Battery Charger Connector: Micro USB type B connector

A new type of multi-measurement remote sensing platform has been presented in this paper that allows a user to reconfigure the sensor’s measurement mode by uploading specialized software apps that are dedicated to particular types of measurements.
    What enables a single instrument to make varied plant physiological and agronomical measurements and estimates, without modifications to the instrument’s hardware, is that each measured/estimated biophysical property is fundamentally related to the spectral reflectance characteristics of the crop canopy.
    Apps for the sensing platform developed thus far include estimators for LAI, biomass, nutrient and yield/vigor.
    Two other apps pertain to data acquisition of plant canopy reflectance, one for point-and-scan measurements and the other for real-time data logging.