Airborne hyperspectral remote sensing enables not only spatial monitoring of vegetation

cover, but also the derivation of individual plant constituents such as chlorophyll and

nitrogen content. These are important parameters for optimised agricultural management

on a field basis through the possibility of spatially differentiated fertilisation and for

hydrological and vegetation yield modelling.

The use of existing airborne imaging spectrometers is cost-intensive. Moreover, it is

difficult to obtain these sensors for multitemporal applications. The imaging spectrometer

AVIS (Airborne Visible/Near Infrared Imaging Spectrometer) was built at the Chair of

Geography and Geographical Remote Sensing of the Ludwig Maximilians University

Munich, Germany, to overcome these difficulties. AVIS is designed as a cost-effective tool

for environmental monitoring using commonly available components. AVIS enables the

deployment of a hyperspectral sensor for both scientific research and educational

purposes. It is based on a direct sight spectrograph coupled to a standard B/W CCD

camera. The signal received by the CCD is read out and sent via a frame grabber card to a

personal computer, where the data is stored on the hard disc together with additional GPS

data. The radiometric, spectral and geometric properties of AVIS resulting from the

calibration procedure are summarised in Table 7-1.

Table 7-1: AVIS characteristics

Parameter Description

Spectral range 553-999nm

Spectral resolution 6nm

Spectral sampling rate / resampling 2nm / 6nm

Number of used bands 74

SNR 45dB (year 1999), 47dB (year 2000)

Spatial resolution 300 pixels per image line

Spatial sampling rate 390 pixels per image line

FOV 1.19rad

IFOV across track 3.1mrad

IFOV along track 2.98mrad

One aim of this thesis was to test the potential of AVIS for the purpose of environmental

monitoring, especially of the chlorophyll and nitrogen status of plants. The land cover

types under investigation were grassland, maize ( Zea mays L.) and winter wheat ( Triticum

aestivum L.). Within this scope, a total of 21 AVIS flights were carried out during the

vegetation periods of the years 1999 and 2000. The AVIS data were preprocessed before analysis, including dark current and flat field correction, resampling as well as atmospheric

correction and reflectance calibration.

The test area chosen for the validation of the AVIS data is located in the northern

Bavarian foothills, 25km southwest of Munich, Germany (48° 6’ N, 11° 17’ E). It is situated

between the Ammersee in the west and the Starnberger See in the east. The

municipalities Gilching and Andechs define the northern and southern borders

respectively.

Within this area, three water protection areas were chosen as test sites. In these test

sites, most of the farmers are under contract to the local agricultural office “ Amt für

Landwirtschaft” resulting in detailed management data for each field. This data include

useful information for the interpretation of ground and AVIS data. Two weather stations of

the Bavarian network of agro-meteorological stations, namely No.72 (Gut Hüll) and No.80

(Rothenfeld), are located in the test area and provide information about precipitation,

temperature and radiation. Ten and thirteen stands were selected as test fields in 1999

and 2000 respectively, including three fields each of maize and wheat in 1999 as well as

three fields of maize and six fields of wheat in 2000. During both years, four meadows

were investigated belonging to the same plant community ( Arrhenatherion elatioris). The

meadows differ in the utilisation intensity (non-fertilised meadow with one cut, meadow

with one cut, meadow with rotational grazing and meadow with four to five cuts).

The ground truth campaigns included weekly measurements of plant parameters, such as

height, dry and wet biomass, phenological stage, chlorophyll and nitrogen content, as well

as a photographic documentation for each field.

The chlorophyll and nitrogen measurements