Don, When we get some ground verification, I'd be happy to do it. For now, there is no local LiDAR data available to me. There is some coverage about a two hours drive from here, but little is on public land and I don't think that any of it has trees much over 100' if they are even that tall. I'm hoping to get some verification in the next month or two on tall trees from Josh in North Carolina. Meanwhile, I'm looking for other sources of free or low-cost unfiltered LiDAR point cloud data and acquiring some tiles adjacent to the first one in the example for further analysis.
Paul ---- [email protected] wrote: ============= Paul-- If you organize this together, I'd like to put it in an upcoming issue of the Bulletin of the ENTS. Don ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Don C. Bragg, Ph.D. Research Forester USDA Forest Service Southern Research Station [email protected] ~~~~~~~~~~~~~~~~~~~~~~~~~~~ The opinions expressed in this message are my own, and not necessarily those of the Southern Research Station, the Forest Service, or the USDA. -----Original Message----- From: Jess Riddle <[email protected]> To: [email protected] Sent: Mon, 9 Mar 2009 10:52 pm Subject: [ENTS] Re: Application of USGS LiDAR data to ENTS, North Carolina example, part 2 Paul, I've been reading all your LiDAR posts with great interest. This is awesome information to see. Even if the heights are off by five to ten feet, this technology would could radically change hunting for tall trees. I keep thinking about all the areas I regard has hit or miss where occasional coves hold exceptionally tall forest but most coves are unimpressive. It looks like LiDAR would allow us to bypass the mundane areas and focus all out time on the exceptional areas. Please keep us updated on your progress! Thanks, Jess On Mon, Mar 9, 2009 at 11:33 PM, Paul Jost <[email protected]> wrote: > I found that Topcon Total Station uses a conversion factor of 1 meter = > 3.280833333333333 survey feet.? So, with more reasonable significant digits, > I updated the TFW or TIFF world file described in Part 1 as follows: > > 3.280833333333333 > 0.0 > 0.0 > -3.280833333333333 > 508729.966942740032947 > 629292.325554704592889 > > Then, with the LiDAR LAS file was converted to a ground points file with the > following command. > > c:\fusion\groundfilter /gparam:-2 /wparam:3 /iterations:10 > c:\lidar\wrightcreek\groundpoints.lda?9 > c:\lidar\wrightcreek\NC_Phase3_2005_35083c8c1.las > > The surface file then was converted to a gridded surface for the software to > use with the following command: > c:\fusion\gridsurfacecreate c:\lidar\wrightcreek\surface.dtm 3 F F 2 0 2 2 > c:\lidar\wrightcreek\groundpoints.lda > > It leaves?a very few?traces of outliers but has the truest lay of the land > without distorting it excessively to make a pretty, perfect visualization.. > State provided maps on the NC DOT web site are less than half the resolution > (20 foot cells vs. 9 foot cells used here.) > > First, I selected a portion of the data for what in the image file looks > like an old growth section of Wright Creek: > > > Then, I subtracted the bare earth surface height from the tree canopy > heights to flatten the image and show only tree heights.? Since we are > looking for big trees, I set the software to color by height and by class > and set it to color?trees up to 130 in blue, in the 130's green, 140' in > yellow, 150's in orange, and above 160 in red.? I set it to exclude?trees > under 150 feet tall.? These pictures are larger to show the content better: > > > Switched it to overhead mode, enabled the measurement marker and set it to > snap measurement marker to highest points.? Then, I enabled the image plate > underneath the data and measured the tree heights.?? By hitting "h" and then > enter, the height is updated and logged.? After logging all the desired > points to check out, I saved the "measurement line" to a .csv file which in > the form of x,y,height. > > Measuring can be done in overhead or 3D modes.? Colors can be smoothly > gradiated or colored by ranges.? You can move the measurement marker tool > over the color coded data view or over the image as shown here.??This is a > tall emergent tree with a large crown.? It may be on a small rise or hump, > or it may actually be a big tree.? Ground truthing will bear it out... > > > > > Regards, > > Paul > > > --~--~---------~--~----~------------~-------~--~----~ Eastern Native Tree Society http://www.nativetreesociety.org Send email to [email protected] Visit this group at http://groups.google.com/group/entstrees?hl=en To unsubscribe send email to [email protected] -~----------~----~----~----~------~----~------~--~---
