IMPROVING GROUND TRUTHING FOR INTEGRATING
REMOTELY SENSED DATA AND GIS*
Qiming Zhou
Petter Pilesjö
School of Geography
University of New South Wales
Sydney 2052, AUSTRALIA
Remote Sensing and GIS Lab
Department of Physical Geography
University of Lund
S-221 00 Lund, SWEDEN
ABSTRACT
Accurate field estimation of vegetation cover is essential for any improvements in rangeland
vegetation modelling and monitoring. This paper reports a recent research project which focuses on
improved field techniques for rangeland vegetation investigation. A semi-arid rangeland field station has
been selected for intensive testing of a number of field techniques employed by pasture management and
remote sensing. The field sampling results from visual estimation, line intercept, quadrat and plant 2-D
crown cover model have been compared with digital images which were acquired from a digital camera
mounted on a five-metre high tripod. The statistical analysis of the sampling results has shown that
visual estimation methods, which are commonly used in rangeland remote sensing, delivered most
unreliable and inconsistent results. The study also shows that a high-level of errors has been associated
with data aggregation while performing rangeland vegetation ground truthing. A new method has been
invented using a remotely controlled digital camera with associated image interpretation methods which
allow accurate and consistent estimates of vegetation cover.
Rangeland constitutes 74% of Australian continent and maintaining the land in a sustainable
condition has been drawing great attention of Australian public. Extensive livestock production is the
major land use on the rangelands with large areas of land required per head of livestock. The rangelands
support large proportion of Australia’s cattle and sheep production which are mainly for export sale, thus
providing substantial input into the domestic economy (Frazier, et al., 1994). Management of rangelands
is ecological in nature, of a low energy input and involving actions that seek to modify, rather than
control, the natural forces operating on the land. To maintain the rangelands in a productive condition, a
land manager must be able to monitor conditions at a level commensurate with the large areas involved,
typically low productivity per unit area, and constraints of labour availability.
Remote sensing technology is recognised as an appropriate tool for rangeland management given
that it is capable of providing information on the state of vegetation on a regular, continuous and near
real-time basis. However, to be useful for land management, remotelv-sensed data must be processed and
* Presented at the International Society for Photogrammetry and Remote Sensing "Workshop on New
Developments in Geographical Information Systems, Milan. Italy, 6-8 March 1996.
1.0 INTRODUCTION