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