Empirical Approaches of Canopy Characteristics Retrieval

Case Study

Phenological Characterization of Agricultural Crop Stands
by Means of Spectroradiometric Data

Contact Persons

Dr. Mathias Kneubühler

Silvia Huber

Keywords

Hyperspectral RS and Agriculture, Field Data Acquisition Techniques, Empirical Methods, Phenology, Vegetation Canopy Parameter Retrieval, In-field Variation, Precision Crop Management

Abstract

Agricultural crops pass through a series of phenological stages from sowing until harvest. The plant's physiological state, reflected by its biochemistry and structural characteristics, constantly changes. This results in spectral changes observable by a remote sensing device. Knowledge of the stage of crop development is necessary for time-specific crop management during crucial periods.
The plants' transition from the vegetative through the reproductive to the senescing phase can be described by a number of parameters that depend on plant vitality. Such parameters are LAI, FAPAR, water content and chlorophyll content. Methods investigated include empirical, semi-empirical and statistical approaches.
Retrieved vegetation canopy parameters can either serve as immediate basis for action in agricultural management or as input (e.g. driving variable, calibration or validation purposes) for agricultural models.

Equipment

Field- and laboratory equipment commonly used for acquisition of spectral data, biophysical and biochemical parameters:

All you need on a typical measurement day:

ASD FieldSpec Pro FR Spectroradiometer:

LAI-2000 Plant Canopy Analyzer:

Sunfleck Ceptometer for FAPAR determination:

Chlorophyll extraction in the laboratory:

Laboratory determination of total leaf area using a LI-COR 3100 Leaf Area Meter:

Determination of leaf chlorophyll content using a CADAS-100 Spectrophotometer:

Results

A)

Phenological development of a spring wheat cultivar observed in the Limpach Valley (Swiss Cantons of Berne and Solothurn) during the 1999 cropping cycle:

Assessment of a crop stands vitality can be performed by relating spectral data to measured variations of biophysical and biochemical parameters.

 

B)

Determination of LAI, FAPAR and Plant Water Content of spring wheat, based on a hyperspectral data set of the HyMap imaging spectrometer flown over the Limpach test site on July 16th 1999. Parameter retrieval is based on semi-empirical and statistical approaches.