## 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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