For historic reasons, mou
ldboar
d p
loughs have a wi
de variety of surfaces. The concentration of manufacturers has re
duce
d the number of
different types but there are sti
ll few comp
lete geometric
descriptions of the surfaces of a mou
ldboar
d p
lough. With the aim of
describing an
d characterizing the three-
dimensiona
l shape of the p
lough, permitting the obtaining of a too
l for an a
dequate preparation of the soi
l for cu
ltivation, as we
ll as re
ducing
labour costs, in this work
different approximation metho
ds of three-
dimensiona
l surfaces have been exp
lore
d. The resu
lts obtaine
d a
llow us to conc
lu
de that the app
lication of non uniform rationa
l B-sp
lines, combine
d with an optimization a
lgorithm base
d on assigning
different weights to the contro
l points of the surface ana
lyze
d, is a metho
d which succee
ds in improving the qua
lity of the fit with respect to other a
lgorithms propose
d by severa
l authors in
different previous works a
lso base
d on the use of sp
lines.
The root mean square error of the fit of these algorithms to a mouldboard plough was the lowest 1.9 mm in the observed, and increases up to 14.4 mm using a simple Bxe9;zier bicubic parametric surface. Using the efficiency index of Nash and Sutclife (1970), the highest value, 0.995, corresponded to the non uniform rational B-splines method.