Power Civil: LIDAR thinning

Re: Power Civil: LIDAR thinning

neilw — Tue, 18 Nov 2008 21:19:33 GMT

I decided to have another try at generating contours from the TIN file and am now able to load them sucessfully. I suspect that during my efforts to find a solution to my task I was loading and unloading other applications that may have left residue in my main memory and caused the allocation problems. Today I sucessfully generated 2' and 10' contours from my UN-thinned TIN consisting of 4.9 million points...impressive!

Re: Power Civil: LIDAR thinning

neilw — Tue, 18 Nov 2008 20:23:57 GMT

Due to the performance problems caused by the large amount of data we have had to clip our study area even more. I was able to trim the data down to about 1 million points and have the TIN built and ported to my Land Desktop Project so I am good to go for now and won't be needing more assistance. However if you still want the data let me know and I will upload to the FTP. Even though I could build the TIN using all 2.5 million points, Power Civil ran out of memory when loading the contours. I was loading 10' and 2' intervals in order to compare with the contours provided with the LIDAR data. Being able to process the data into a TIN is only part of the battle.

Re: Power Civil: LIDAR thinning

Robert Garrett — Tue, 18 Nov 2008 18:17:07 GMT

In the mean time, here is a suggestion that perhaps will help get you underway:

You have already used the LIDAR tools to clip to your desired area. Instead of one large clipped area of 2.5 million points, clip to multiple smaller areas.
Then filter each of these smaller areas
Then merge the smaller areas into a complete TIN.

Not the most efficient method, sure, but if you are facing a deadline.

Note: Pay special attention to the edges where the multiple small TINs merge back together to check for oddities after they are merged.

Re: Power Civil: LIDAR thinning

Robert Garrett — Tue, 18 Nov 2008 17:35:08 GMT

Good Morning Neil

The 30 million number apprently comes from our help file. (Thanks Mike). My experience still indicates that your computer is choking on the size of the data. But I am investigating. I have a LIDAR test set, but if you can send me a link to your your LIDAR file then I will look at yours. Or post it at ftp://ftp.bentley.com/pub/incoming and send me an email when it arrives.

Re: Power Civil: LIDAR thinning

neilw — Tue, 18 Nov 2008 01:58:36 GMT

I did thin the data as far as I dared to. Z filter was 1.0 which gave marginal results. Actually Power Civil is handling it pretty well considering the size. The 30 million points info came from various inside sources. Not to say that is an official claim, but I believe it is in a blog or forum somewhere as well.

I managed to get the data into my other applications by using the same thinned XYZ file so the XML export is no longer necessary at this time.

It looks like we are going to need to move to a 64 bit OS soon with data like this becoming more and more common.

Re: Power Civil: LIDAR thinning

Robert Garrett — Tue, 18 Nov 2008 01:50:44 GMT

Neil - 2.5 million points is a fairly huge DTM. Not sure who advised you that you should be able to do 30 million. WIll PowerCivil do 30 milliion? Maybe, but probably not on a 2GB machine. Don't forget that your operating system and other processes will take a huge chunk out of the available memory. Looking right now at my computer, I have eaten up over 3/4GB and I haven't even opened PowerCivil yet.

Your memory allocation errors are telling you what the problem is. Your machine is, quite simply, choking on the huge amount of data in the TIN processing. This is why we built the LIDAR tools in the first place. LIDAR tools are so huge that they tend to choke everybodies computer.

I would advise trying a little more agressive settings in the thinning and compare the results to insure that you don't go too far.

Re: Power Civil: LIDAR thinning

neilw — Tue, 18 Nov 2008 00:06:49 GMT

Update: I got the thinning tools to work but starting on a fresh reboot. The thinned data file is 2.5 milliion pts. I built a TIN and can load the TIN features such as contours nicely. However I am still crashing when trying to export to XML.

Re: Power Civil: LIDAR thinning

neilw — Mon, 17 Nov 2008 23:33:49 GMT

I am now finding that I cannot export the clipped, un-thinned TIN to XML. Power Civil is giving Memory allocation errors when exporting as well. I understand that the DTM tools are capable of handling 30 million points so I am hoping that the memory errors are not due to a size limitation.