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Title
Remote sensing for resources development and environmental management
Author
Damen, M. C. J.

Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986
257
Spectral signature of rice fields using Landsat-5 TM
in the Mediterranean coast of Spain
S.Gandia, V.Caselles, A.Gilabert & J.Melia
Department of Thermology, Faculty of Physics, University of Valencia, Spain
ABSTRACT: This work gives the first results of a study carried out in an agricultural area of the Spanish Mediterranean coast using
Thematic Mapper images. Three cover types, rice, citric - vegetable orchard and urban area are classified in the zone by using a
vegetation index. Bands 4 and 5 seem to be more suitable for a possible classification of two varieties of rice.
Key words: Thematic Mapper, vegetation index, rice plants.
RESUME: Ce travail donne les premiers résultats d'une étude réalisé dans une zone agricole de la côte méditerranéenne espagnole en
utilisant des images du Thematic Mapper. Trois types de couverture du sol (riz, agrumes-legumes et une zone urbaine) ont été classées.
Les canaux 4 et 5 semblent les plus convénianu» pom une distinction de deux variétés de riz.
Mots clés: Thematic Mapper, index de végétation, cultures rizières.
1. INTRODUCTION
The application of radiometric measurements to the study of the
spectral response of rice has originated a number of publications.
A fair amount of the experimental measurements have been
ground-based radiometric ones and have mainly addressed to
establishing correlations among parameters of an agricultural
interest such as production, influence of the use of different
fertilizer treatments (Patel, 1985), (CCE.1978), (Berg, 1980),
etc. Air - flight images as well as images carried out from
satellites, especially with the Landsat MSS have also originated
frequent works (CCE, 1984).
The Thematic Mapper (TM) sensor of the Landsat 5 provides
better achievements with respect to the MSS which gives it a
greater potentiality in regards to thematic mapping techniques. In
regions with high ground parcelation the increase of spatial
resolution from 80 m (for the MSS) to 30 m (for the TM) is
essential. In the same way, the inclusion of new spectral bands,
B1 (0.45 - 0.52 pm), B5 (1.55 - 1.75 pm) and B7 (2.08 - 2.35
pm) allow a more complete definition of spectral signatures. The
increased quantization level of 6 bits (0 - 63) to 8 bits (0 - 255) is
very important in areas where besides high parcelation, different
agricultural cultivations alternate with urban areas. D. L. Toll
(Toll, 1985) carries out an important study comparing the
different characteristics of TM and MSS sensors for land cover
classification.
The present work gives the first results of rice studies carried
out in an area of the Spanish Mediterranean coast from
measurements supplied by the satellite Landsat 5 (TM).
2. STUDY SITE DESCRIPTION AND DATA USED
Approximately a third of Spanish rice production is obtained at
the south of the city of Valencia (Spain) which is an area
eminently agricultural. The area of cultivation (about 15.500 ha)
expands along the lands bordering the lake "La Albufera" and the
proximities of the outfall of the Jucar river, "Ribera Baixa". This
is a high populated area where rice cultivations alternate with
citrics and vegetables. The lands dedicated to the cultivation of
rice are slowly but constantly decreasing because they are being
substituted by orchards and citrics. The map of figure 1 shows
the referred area and the two studied zones.
But this seaboard stripe is also undergoing a strong urban
pressure characteristic of tourist areas. Similarly La Albufera lake
and its surroundings is an area of general interest due to the
alterations produced in the natural environment.
The heterogeneity of land cover types besides the big ground
parcelation impose the use of satellite measurements with high
spatial resolution for the classification of the ground.
In this study two neighbouring zones of about 7 km 2 each
have been chosen (figure 1). The lower one (Sueca)
representative of the different land cover types: rice, citric -
Figure 1. Training sites located in the Mediterranean coast of
Spain.
vegetable orchards and urban areas and has been defined in order
to separate these three land cover classes. The upper zone (La
Albufera) mainly contains rice fields. The work has been
centered in this area in order to study the spectral response of
rice.
In both zones, reference parcels have been chosen, with the
caracteristics shown in Table I. The varieties Bahia (91%) and
Sequial (8%) cover almost exclusively the whole production.The
net efficiency is about 6500 kg/ha. Parcels with other varieties
(Rubino, Pierina and Lido) have been taken in order to study
reflectivities. These latter parcels are considered experimental
from a production point of view.
The citric - vegetable class presents a great internal variability
due to the different degree of vegetated cover of the ground. In
these class other types of cultivations such as vegetables have
been included in order to discriminate them from rice.