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NAME

v.lidar.edgedetection - Detect the object's edges from a LIDAR data set.

KEYWORDS

vector, LIDAR, edges

SYNOPSIS

v.lidar.edgedetection
v.lidar.edgedetection help
v.lidar.edgedetection input=name output=name [see=float] [sen=float] [lambda_g=float] [tgh=float] [tgl=float] [theta_g=float] [lambda_r=float] [--overwrite]

Flags:

--overwrite
Force overwrite of output files

Parameters:

input=name
Name of input vector map
output=name
Name for output vector map
see=float
Interpolation spline step value in east direction
Default: 4
sen=float
Interpolation spline step value in north direction
Default: 4
lambda_g=float
Regularization weight in gradient evaluation
Default: 0.01
tgh=float
High gradient threshold for edge classification
Default: 6
tgl=float
Low gradient threshold for edge classification
Default: 3
theta_g=float
Angle range for same direction detection
Default: 0.26
lambda_r=float
Regularization weight in residual evaluation
Default: 2

DESCRIPTION

v.lidar.edgedetection is the first of three step to filter LIDAR data. It detects the edge of each single feature over the terrain surface of a LIDAR point surface. First of all, those points with a high gradient value are determined. Then, it is valued the difference between the observation of those points and a generic interpolated surface with splines. If the difference is positive, then the point could supposed to be inside the object, else the point could supposed to be outside the object. The final output will be a vector map in which points has been classified as TERRAIN, EDGE or UNKNOWN. This output will be the input of v.lidar.growing module.

NOTES

In this module, an external table will be created which will be useful for the next module of the procedure of LIDAR data filtering. In this table the interpolated height values of each point will be recorded. The final result of the whole procedure (v.lidar.edgedetection, v.lidar.growing, v.lidar.correction) will be a point classification in four categories:
TERRAIN SINGLE PULSE
TERRAIN DOUBLE PULSE
OBJECT SINGLE PULSE
OBJECT DOUBLE PULSE

EXAMPLES

Basic edge detection

v.lidar.edgedetection input=vector_last output=edge see=8 sen=8 lambda_g=0.5

SEE ALSO

v.lidar.growing, v.lidar.correction

AUTHORS

Original version of program in GRASS 5.4:
Maria Antonia Brovelli, Massimiliano Cannata, Ulisse Longoni and Mirko Reguzzoni

Update for GRASS 6.X:
Roberto Antolin and Gonzalo Moreno

REFERENCES

Brovelli M. A.; Cannata M.; Longoni U.M., 2004, LIDAR Data Filtering and DTM Interpolation Within GRASS, Transactions in GIS, April 2004, vol. 8, iss. 2, pp. 155-174(20), Blackwell Publishing Ltd

Brovelli M. A., Cannata M., 2004, Digital Terrain model reconstruction in urban areas from airborne laser scanning data: the method and an example for Pavia (Northern Italy). Computers and Geosciences 30 (2004) pp.325-331

Brovelli M. A. e Longoni U.M., 2003, Software per il filtraggio di dati LIDAR, Rivista dell?Agenzia del Territorio, n. 3-2003, pp. 11-22 (ISSN 1593-2192)

Brovelli M. A., Cannata M. and Longoni U.M., 2002, DTM LIDAR in area urbana, Bollettino SIFET N.2 ?2002, pp. 7- 26

Last changed: $Date: 2007/04/16 21:36:04 $

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