that there is an imminent risk of underestimating or even not realising the weeds or
weed patches. Five significantly different maps have been produced from five
different starting points of sampling Regarding the weed
species analysed (Chenopodium album L., Stellaria media L.) in this paper and their
biological features, there appears to be a close correlation between the credibility of
the weed map produced from grid (a) and the distribution of the weeds in nature.
Weeds occurring scattered all over the field appear to be largely overestimated by grid
(a), whereas weeds that occur in a clustered way are mapped completely different or
not at all (Table1; Table 2). In this study six different weed species, including the
category of all gramineous plants (e.g. Echinochloa crus-galli L. and Avena fatua L.,
not shown in a map) as one group were analysed. The exemplified species are
representative for the other species which have not been mentioned in this paper.