LIDAR Help

Noklu

Here in Pennsylvania we have a wealth of free lidar data I would like to use in some of our planning projects. I have no problem loading the data, however, when everything is loaded there seem to be "stray" points floating high above the surface. When I try to build a grid or tin they create these tall spikes. First off, what are these? Second, how can I filter them out? I have attached a 3d view of the points loaded, they are hard to see but are the red dots floating in mid air. Any help is appreciated.

global_mapper

This is common in Lidar data sets. Often there will be stray samples that are far from the surrounding elevation values. We are going to add a way to automatically identify those and mark those as deleted when loading the data, but you can also use the Search option to automatically find and delete them. Sometimes there are also classified as low points/noise so you can just turn that type off when loading the LAS file.

Thanks,

Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.bluemarblegeo.com/

Noklu

Mike,
Thanks for getting back to me. I tried using the search feature to filter by elevation, but the search does not find any results. How should I phrase the search?

global_mapper

There was actually a bug in the v14.1.0 release that made searching by elevation on the Lidar point clouds not work. In the latest builds the search should work as you'd expect by searching numerically on the elevation. I have placed a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14.zip with the latest changes for you to try. Simply download that file and extract the contents into your existing v14.xx installation folder to give it a try. If you are using the 64-bit v14 version there is a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14_64bit.zip .

Thanks,

Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.bluemarblegeo.com/

Noklu

Thanks Mike. That worked perfectly.

global_mapper

I have just added something to make this much easier and faster. Now when you load a Lidar file (LAS/LAZ) you can specify to mark any points outside some number of standard deviations from the mean as deleted. So you might try deleting points more than 2 or 3 standard deviations from the mean and see if that takes care of your problem points. I have placed a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14.zip with the latest changes for you to try. Simply download that file and extract the contents into your existing v14.xx installation folder to give it a try. If you are using the 64-bit v14 version there is a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14_64bit.zip .

Thanks,

Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.bluemarblegeo.com/

Noklu

Thank you Mike. This is why Global Mapper is the best!