NOTES
M
isclassification in the procedure
output remains, due to particular geometry of some objects (the
simplest we can recall is the case where we have unusual roofs
with pitches at different heights).
To overcome
this problem, a bilinear interpolation with
Tikhonov regularising parameter lambda_c only on
the points classified as bare earth is performed. The
analysis of the residuals (D) between
the observations and the interpolated values compared with two
thresholds tc
,Tc show four cases:
·
if the point is
classified as
ground and D > Tc , it is
reclassified as object;
·
if the point is
classified as
‘double pulse ground’ and D > Tc
, it is reclassified as ‘double pulse object’ (edge or vegetation);
·
if the point is
classified as
object and |D| < tc , it
is
reclassified as ground;
·
if the point is
classified as
‘double pulse object’ and |D| < tc,
it is reclassified as ‘double pulse ground’.
Every point
of the input site file is examinated and reclassified in the output file as:
·
terrain (0)
·
terrain with
double pulse (1)
·
object with
double pulse (2)
·
object (3)
input format example (x|y|z):
499453.39|5418722.51|#0
%245.99 %1
499453.52|5418725.56|#0 %246.19 %1
499453.67|5418728.67|#0 %246.2 %2
499453.81|5418731.8|#0 %246.2 %3
499453.9|5418734.65|#0 %247.13 %0
499454.66|5418734.31|#0 %246.99 %0
output format
example (x|y|z%classification%bicubic_interpolated_value):
499453.39|5418722.51|#0 %245.99 %1
499453.52|5418725.56|#0 %246.19 %2
499453.67|5418728.67|#0 %246.2 %1
499453.81|5418731.8|#0 %246.2 %0
499453.9|5418734.65|#0 %247.13 %0
499454.66|5418734.31|#0 %246.99 %0
SEE ALSO
s.edgedetection, s.bspline, s.growing, s.to.qrast
AUTHORS
Maria
A. Brovelli, Politecnico di Milano - Campus Como
Massimiliano Cannata, Politecnico
di Milano - Campus Como
Ulisse M.
Longoni, Politecnico
di Milano - Campus Como
REFERENCES
Brovelli M.A.;
Cannata M.; Longoni U.M., LIDAR Data Filtering and DTM Interpolation
Within GRASS
Transactions in GIS, April 2004, vol. 8, no. 2, pp.
155-174(20) - Blackwell Publishing Ltd