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Critical sample size and satellite image selection for the recognition of poppy and pyrethrum crops in North West Tasmania


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Barrett, Rachel Michelle 2002 , 'Critical sample size and satellite image selection for the recognition of poppy and pyrethrum crops in North West Tasmania', Research Master thesis, University of Tasmania.

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Determination of the critical level of training data, and investigation of targeting
the time of image acquisition to specific crop growth cycles, will increase the
efficiency of remote sensing data analysis, for recognition of poppies and
pyrethrum. The objective of this project, was to determine whether the amount of
training data (critical sample size) contributed significantly to classification, using
three methods of analysis of two season's data for, poppy and pyrethrum crops, on
the North West Coast of Tasmania and to investigate the timing of image
acquisition. Distinction between class types was not an objective of the study.
Eight Landsat 5 TM, two SPOT XS and three SPOT XI images were acquired
between 02 July 1997 and 28 March 1999.
Observations of the spectral response of poppies showed that, Landsat TM bands
one, two, three and five in November and January, provided significantly
different, peak pixel values for the poppy crop. SPOT XS band two in February
also provided peak pixel values for poppies. The spectral response of pyrethrum
indicated that an increase in pixel value for the January Landsat TM data in bands
five and seven was distinct, as was the peak in SPOT XI band three during
A principal component analysis, (PCA) was carried out separately on each image.
For all Landsat TM imagery, over 98.482% of variance was contained within the
first three principal components. Similarly, for all SPOT XI data, over 99.189% of
variance was contained within the first three principal components. When SPOT
XS data was analysed, the first and second components accounted for over
98.909% data variance.
The merged spectral response patterns generated from the automatic internal
average relative reflectance (AIARR), normalised difference vegetation index
(NDVI) and PCA images by an unsupervised, iterative self-organising data
analysis technique (ISODATA) for the poppy and pyrethrum AOIs, provided the
input for a supervised classification. As the AIARR, NDVI and PCA data were
normally distributed, and the spectral response patterns were parametric, a
maximum likelihood parametric decision rule was selected.
The amount of training data had a significant effect on the contribution to
classification for the three analysis methods, over two season's data for each of
the crop types.
To achieve a classification accuracy of 90% for poppies, the acquisition of
Landsat data in either November or January, required a PCA with 80% of the total
poppy area used as training (calibration) data. To achieve a classification accuracy
of 96% for poppies, the acquisition of SPOT XI data in either October or
December, required a NDVI analysis with 50% of the total poppy area used as
training (calibration) data.
For pyrethrum, a classification accuracy of 80% was achieved by acquiring
imagery in the post harvest and dormancy stage (late February to October), using
a PCA method and 90% of the total amount of data available for training. When
imagery was acquired in late December or early January, using 40% of the total
amount of pyrethrum data for training contributed, on average, to the
classification of 87% of the crop, when analysed using the NDVI method.
The findings of this research showed that the choice of the training set (quality
and quantity) had an influence on the success of a classification approach as well
as the choice of image analysis technique. Timely acquisition of imagery was
shown to be required to achieve a satisfactory level of contribution to
classification from training data of poppies and pyrethrum.

Item Type: Thesis - Research Master
Authors/Creators:Barrett, Rachel Michelle
Keywords: Crops, Poppies, Pyrethrum (Plant), Land use, Landsat satellites
Copyright Holders: The Author
Copyright Information:

Copyright 2002 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (M.Agr.Sc.)--University of Tasmania, 2002. Includes bibliographical references

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