Change Detection of Vegetation Using Lidar

[aykut yiğit]

Hi, I am new about Lidar data and have project. I have some questions about my project. I have two Lidar datasets from 2009 and 2013 and need to detect changes for vegetation between two time periods. The 2009 datasets does not have correct classification, so vegetation or buildings points are not obvious. My question is what I should do to detect vegetation changes. How can I extract vegetation regions to compare? I will be glad if you helped me about these issue. Thank you very much

[Martin Isenburg]

Hello,

if your data is not correctly classified into buildings and vegetation you can use the usual LAStools processing pipeline to reclassify your LiDAR and see if you like the result better. How to do this is described in these introductory tutorials:

http://rapidlasso.com/2013/04/20/tutorial-quality-checking/
http://rapidlasso.com/2013/10/13/tutorial-lidar-preparation/
http://rapidlasso.com/2013/10/20/tutorial-derivative-production/
http://rapidlasso.com/2014/09/02/six-new-video-tutorials-on-lastools/

And there are about 50 hours of LAStools YouTube videos online:

http://www.youtube.com/playlist?list=PLWxNVlb9ZPRpkGKfQGz8xpymSRQweounQ
https://www.youtube.com/playlist?list=PL5A2DB97AA32C1A3B

In order to you all vegetation I often recommend to only drop the building class (-drop_class 6) instead of keeping the vegetation points (-keep_class 5) as by default we only classify vegetation points above 2 meters and also tend to miss a few smaller trees and shrubs.

From all points (minus the building points) you can then construct pit-free CHMs using either the pit-free [1] or the spike-free [2] algorithm and then compare the elevation of the resulting CHM rasters for differences.

[1] http://rapidlasso.com/2014/11/04/rasterizing-perfect-canopy-height-models-from-lidar/

[2] http://rapidlasso.com/2016/02/03/generating-spike-free-digital-surface-models-from-lidar/

Regards,

Martin @rapidlasso

On Tue, Aug 30, 2016 at 1:11 AM, aykut yiğit <aykut....@gmail.com> wrote:

Hi, I am new about Lidar data and have project. I have some questions about my project. I have two Lidar datasets from 2009 and 2013 and need to detect changes for vegetation between two time periods. The 2009 datasets does not have correct classification, so vegetation or buildings points are not obvious. My question is what I should do to detect vegetation changes. How can I extract vegetation regions to compare? I will be glad if you helped me about these issue. Thank you very much

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