[GRASS-user] v.lidar.edgedetection very slow

John Tate john.tate at ntlworld.com
Thu Jun 18 13:00:07 EDT 2009

Hi all,

I have recently joined the user group and I'm working on LiDAR data.

I have worked alot of things out from the book and fiddling but have a question regards this.

I am running GRASS GIS 6.4.0svn (the one that came out last week) on an Intel quad core 6600 with 2gb RAM.

I have seperated my data into 1000mx1000m which have around 1.5 million points per tile.

I use the -tbzr on v.in.ascii and v.build after for topology. I have also utilised the sqlite db.

After running v.outlier on first and last returns, the time come for edge detection.

I run this module (v.lidar.edgedetection) and it works (only using 25% of cpu as per usual (guessing there is no quad cpu support = shame)) However, I have not finished a process yet as it writes at about 1kb per second, using 1% of cpu.

Is it supposed to be this slow? is there a bug? The tile as .txt/.las is c.47Mb. Does the edge file equate to a similar size, e.g. will it take about 47000 seconds to write the file? Is there a rough percentage of the size of edge file compared to original txt file? I notice it is also writing to the sqlite.db at the same time.

Have I done something wrong?

I would appreciate some feedback of other peoples experiences of v.edgedetection in this version and earlier version of win GRASS.

Cheers, and hope someone can help

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