Sources of Uncertainty in Land Use Pressure Mapping

L.R. Lilburne and H.C. North
Landcare Research
P.O. Box 69, Lincoln, Canterbury 8152, New Zealand
Ph. +64 3 3256700; Fax +64 3 3252418
E-mail: lilburnel@landcareresearch.co.nz

Abstract
A key agricultural management pressure in Canterbury, New Zealand, is the practice of leaving land fallow during winter, because any nitrate present is likely to  be leached since there is no plant uptake. Remote sensing imagery has been successfully used to identify  land bare for significant periods in winter and early spring. This was achieved by use of simple rules  on a temporal sequence of three Landsat 7 images. In particular, ability to correctly classify land into bare, sparsely vegetated, and fully vegetated categories according to percentage cover of vegetation was investigated using detailed field data along with the images. This paper analyses the sources of error in mapping fallow ground using remote sensing image sequences. Accurate assessment of total area and correct assessment at each spatial location were the aims. Potential sources of error include suitability of the logical  model, timing of image acquisition, scale mismatch, incorrect reference data, geometric errors between  images, and radiometric variation both within and between images (month to month and year to year). A probabilistic approach to providing estimates of uncertainty was applied to draw together the most important of these error sources. Radiometric error was the most significant error source. A map of uncertainty is also produced.

Keywords: landuse pressure, multi-temporal, radiometric error, geometric error

In: McRoberts, R. et al. (eds).  Proceedings of the joint meeting of The 6th International Symposium On Spatial Accuracy Assessment In Natural Resources and Environmental Sciences and The 15th Annual Conference of The International Environmetrics Society, June 28 – July 1 2004, Portland, Maine, USA.

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