
%0 Journal Article
%A Hassett, R. C. 
%A Wood, H. L. 
%A Carter, J. O. 
%A Danaher, T. J. 
%T A field method for statewide ground-truthing of a spatial pasture growth model
%J Australian Journal of Experimental Agriculture
%D 2000/12/21
%V 40
%N 8
%P 1069-1079
%K model calibration, model validation.
%R https://doi.org/10.1071/EA00010
%U https://www.publish.csiro.au/paper/EA00010 
%X This paper describes an innovative method, commonly referred to as &#8216;spider mapping&#8217;, that allows pasture biomass and related data to be collected over large areas in a timely and efficient manner. Spider mapping was developed initially to collect data to allow calibration and validation of a spatial and temporal pasture growth model operating across Queensland on a 5 km grid basis. Two field officers made over 220 000 estimates and collected about 1300 samples of pasture biomass between January 1994 and August 1995. A number of selected biomass samples were analysed for nitrogen, phosphorus and carbon content. In addition, data were also collected on foliage projective cover and tree basal area for a range of woodland communities and both variables compared with mean long-term Normalised Difference Vegetation Index values derived from a time series of National Oceanographic and Atmospheric Administration satellite imagery. Both variables were strongly related to the satellite data with overstorey foliage projective cover having the strongest non-linear correlation (r2 = 0.91). The method described here is currently being used in related work in the rangelands of New South Wales, South Australia, Western Australia and the Northern Territory. 
