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Spectral characterisation and mapping of Welwitschia Mirabilis in Namibia


Kellenberger, R; Kneubühler, M; Kellenberger, T (2009). Spectral characterisation and mapping of Welwitschia Mirabilis in Namibia. In: IEEE International Geoscience and Remote Sensing Symposium, Cape Town, ZA, 12 July 2009 - 17 July 2009.

Abstract

Remote Sensing bears the potential to contribute towards
identification and mapping of endemic and endangered
plant species. This study assesses the spatial distribution of Welwitschia mirabilis, an ancient desert plant species, in its natural habitat, Africa’s Namib desert. Welwitschia
mirabilis is one of the oldest plants in existence; some
plants reach an age of up to 1500 years. Considered as a
living fossil, the plant is difficult to map both due to the
fragile ecosystem in which it lives, and the fact that a large part of its indigenous area is inaccessible as a result of diamond mining.
In a first step, various Welwitschia individuals from
botanical institutions within Switzerland are spectrally
characterized using an ASD FieldSpec3 spectroradiometer.
These data sets are investigated to a) identify potential
spectral differences within and among individuals and b)
elaborate possible common spectral characteristics of the
genus usable for remote sensing recognition. The results of
these experiments show that the overall spectral behaviour
of Welwitschia does not represent potential influencing
factors like plant age, plant stress and environment, which
makes the signal suitable for remote sensing species
detection.
In a second step, mapping of individual Welwitschia plants
is performed in a valley of the Namib-Naukluft Park using
multispectral IKONOS satellite data of high spatial
resolution. The plant species are classified using a
maximum likelihood approach. It can be concluded that
with the IKONOS data used, an adequate result may only
be achieved under ideal conditions where Welwitschia
individuals and additional plants (e.g., acacias, bushes)
grow apart from each other on a homogeneous background
consisting of bright gravel and sand. Despite the huge
amount of shadow fractions within a plant pixel due to the
spatial resolution of the image, the species Welwitschia was
successfully detected by its typical spectral signal.
Spatial and spectral resolution remain a limiting factor in
accurately mapping individual Welwitschia species and
detecting them in a heterogeneously vegetated environment.
Future spaceborne sensors of higher spatial and spectral
resolution can further contribute towards an improved
assessment of plant individuals from space and may
therefore support the detection of threatened, invasive or
prohibited species.

Remote Sensing bears the potential to contribute towards
identification and mapping of endemic and endangered
plant species. This study assesses the spatial distribution of Welwitschia mirabilis, an ancient desert plant species, in its natural habitat, Africa’s Namib desert. Welwitschia
mirabilis is one of the oldest plants in existence; some
plants reach an age of up to 1500 years. Considered as a
living fossil, the plant is difficult to map both due to the
fragile ecosystem in which it lives, and the fact that a large part of its indigenous area is inaccessible as a result of diamond mining.
In a first step, various Welwitschia individuals from
botanical institutions within Switzerland are spectrally
characterized using an ASD FieldSpec3 spectroradiometer.
These data sets are investigated to a) identify potential
spectral differences within and among individuals and b)
elaborate possible common spectral characteristics of the
genus usable for remote sensing recognition. The results of
these experiments show that the overall spectral behaviour
of Welwitschia does not represent potential influencing
factors like plant age, plant stress and environment, which
makes the signal suitable for remote sensing species
detection.
In a second step, mapping of individual Welwitschia plants
is performed in a valley of the Namib-Naukluft Park using
multispectral IKONOS satellite data of high spatial
resolution. The plant species are classified using a
maximum likelihood approach. It can be concluded that
with the IKONOS data used, an adequate result may only
be achieved under ideal conditions where Welwitschia
individuals and additional plants (e.g., acacias, bushes)
grow apart from each other on a homogeneous background
consisting of bright gravel and sand. Despite the huge
amount of shadow fractions within a plant pixel due to the
spatial resolution of the image, the species Welwitschia was
successfully detected by its typical spectral signal.
Spatial and spectral resolution remain a limiting factor in
accurately mapping individual Welwitschia species and
detecting them in a heterogeneously vegetated environment.
Future spaceborne sensors of higher spatial and spectral
resolution can further contribute towards an improved
assessment of plant individuals from space and may
therefore support the detection of threatened, invasive or
prohibited species.

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Additional indexing

Item Type:Conference or Workshop Item (Paper), not refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Geography
Dewey Decimal Classification:910 Geography & travel
Language:English
Event End Date:17 July 2009
Deposited On:01 Oct 2009 16:02
Last Modified:14 Aug 2016 07:03
Additional Information:Copyright 2009 IEEE. Published in the IEEE 2009 International Geoscience & Remote Sensing Symposium (IGARSS 2009), scheduled for July 13-17, 2009 in Cape Town, South Africa. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works, must be obtained from the IEEE. Contact: Manager, Copyrights and Permissions / IEEE Service Center / 445 Hoes Lane / P.O. Box 1331 / Piscataway, NJ 08855-1331, USA. Telephone: + Intl. 908-562-3966.
Publisher DOI:https://doi.org/10.1109/IGARSS.2009.5417388
Official URL:http://www.igarss09.org/default.asp
Permanent URL: https://doi.org/10.5167/uzh-20750

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