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What is the difference between a datum and its ellipsoid? Evon of +Quantum Spatial gave this answer [1] in the +LAStools user forum:

An ellipsoid is a mathematical shape defined by two radii while the datum defines the position of that ellipsoid relative to the center of the Earth. Every datum must have one reference ellipsoid, but not every ellipsoid has necessarily just one datum.

Take the following graphic with an ellipsoid as defined by its major and minor radii and an exaggeration of Earth's irregular surface. Below that I show three possible configurations of the exact same ellipsoid relative to the earth - a bad fit, a biased fit, and a best fit.

Although the same ellipsoid is used every time, the way that it fits the center and surface of the Earth varies. This is implicitly defined by the datum definition.

(1) The bad fit is mostly shown as an example, but I'm sure that someone can come up with a scenario where it makes sense - maybe an extremely localized datum?

(2) The biased fit represents an attempt to match the ellipsoid to a particular region; this is the approach taken for NAD83, which tries to fix the datum to the North American tectonic plate.

(3) The best fit, by contrast, attempts to match the ellipsoid to the center (or surface) of the earth as closely as possible; this is the approach taken for WGS84.

Therefore, defining the ellipsoid is not enough to uniquely define your file's coordinate system. We also need to define the horizontal datum.

[1] http://groups.google.com/d/topic/lastools/Id8fNoABYEI/discussion
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Latin America will see its premier #LiDAR  event of 2015 as +LAStools, #CloudCompare , and +OpenTopography Facility come for a three day workshop to CICESE in Mexico. Dr. Alejandro Hinojosa has done magic to bring together (for the first time) a dynamic group of well-known LiDAR‬ enthusiasts in the coastal town of Ensenada, Baja California one hour South of Tijuana (just across the US border) ... (-;
PRESS RELEASE (for immediate release) March 9, 2015 rapidlasso GmbH, Gilching, Germany The week after Easter is poised to see Latin America's premier LiDAR event of 2015 when LAStools, CloudCompare...
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LAStools

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What is the position of the #ASPRS  on the "LAZ clone"? +Esri is promoting their lock-in #LiDAR  format by the name of the open LAS specification (for which the ASPRS holds the copyright) calling their closed format “Optimized LAS“. We have been asked (in various forums) about the position of the ASPRS on this issue. So far they have not released a statement on ESRI’s closed version of the #LAS  format ...
We are concerned about ESRI's next moves in forcing yet another proprietary format into wide-spread deployment. Forwarded emails, retold conversations, and personal experiences suggest that sneaky ...
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Yet another answer reached us in reaction to +Esri's unpopular "LAZ clone" and the lock-in attempt behind their closed format. The Alaska Division of Geological and Geophysical Surveys has informed us about an update to their #LiDAR  download portal that now hosts a total of 144,005,309,282 points in 48,260 files covering 9,123 square miles. The data - stored compressed with #LASzip  - is still a whopping 645 GB ... (-:

http://www.facebook.com/LAStools/photos/851357821593330
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Dear LAStools friends and users, 

it's the time of the year where people make lists. Here is the top ten in number of clicks on our articles at http://rapidlasso.com/blog over the course of 2014 ... 

1.) the all time favorite: the QGIS toolbox for LAStools 
http://rapidlasso.com/2013/09/29/how-to-install-lastools-toolbox-in-qgis/ 

2.) a surprise runner-up posted in late 2014. don't be evil, Esri!!! 
http://rapidlasso.com/2014/11/06/keeping-esri-honest/ 

3.) our "LAZ clone" announcement days before the official release 
http://rapidlasso.com/2013/12/30/new-compressed-las-format-by-esri/ 

4.) the ArcGIS toolbox is popular but QGIS had 6 times more clicks 
http://rapidlasso.com/2013/07/02/arcgis-lastools-toolbox-for-lidar-processing/ 

5.) part 2 of 3 simple tutorials on LAStools #LiDAR  processing 
http://rapidlasso.com/2013/10/13/tutorial-lidar-preparation/ 

Here a note to our LiDAR and geospatial media outlets: The proprietary "LAZ clone" and the worrisome LiDAR format lock-in attempts by ESRI was one of the top and most controversial news stories of 2014 (and will continue to be in the future). My wish for 2015 is that you are less worried about your sponsorship dollars and more concerned about reporting on all the stories that matter to your readers. The April Fools' Day press release that tricked you into reporting on what ESRI should have done (which came it as number 12) does not count ... (-; 

http://rapidlasso.com/2014/04/01/esri-and-rapidlasso-develop-joint-lidar-compressor/ 

Happy 2015!!! 

Martin @rapidlasso 

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For this curious, here the remaining 5 that complete the top ten: 

6.) our lazer-war-themed announcement of the RIEGL VUX-1 
http://rapidlasso.com/2014/02/01/clone-wars-and-drone-fights/ 

7.) LAStools are getting popular for photogrammetry point clouds 
http://rapidlasso.com/2014/06/13/dtm-from-dense-matching-points/ 

8.) an unscripted success moment at QGIS + LAStools workshop 
http://rapidlasso.com/2014/05/23/first-ever-lidar-processing-model-in-qgis/ 

9.) new ArcGIS toolboxes for multi-core tile-based LiDAR processing 
http://rapidlasso.com/2014/04/03/new-lastools-production-and-lastools-pipelines-for-arcgis/ 

10.) comparing RIEGL and Optech: average point density is not all 
http://rapidlasso.com/2014/03/20/density-and-spacing-of-lidar/
We had an ArcGIS LiDAR processing toolbox since April 2012 and now we have one for QGIS as well. It has been tested successfully with QGIS 1.8.0-Lisboa, 2.0.1-Dufour, 2.2.0-Valmiera, and 2.4.0-Chug...
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Flying #LiDAR  together with Asian Aerospace Services Ltd. above the Khao Yai National Park in Thailand, #rapidlasso  was able to collect unique full waveform data of a dense tropical rainforest canopy in #PulseWaves  format. Unfortunately the #TREEMAPS  project of +WWF Thailand had its funding pulled due to local political wrangling. But we can provide the data collected on our pro-bono test flight as #opendata  with a +Creative Commons Public Domain license ... (-:
Scanning forests with LiDAR is done to predict timber yield, estimate biomass, and monitor ecosystems. A detailed Digital Terrain Model (DTM) is needed to accurately compute forestry metrics such a...
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LAStools

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A feature request from my users of the DREAM #LiDAR  Program in the Philippines was multiple file deletion in the GUI. It's now available in the newest (150330) version of +LAStools:
(1) click the pick button
(2) draw a rectangle covering (even in parts) the files to delete
(3) press the <DELETE> key
Here an explanatory sequence of three GUI screenshots.
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The latest participant of our program "LASmoons - free licenses for poor LiDAR lunatics" is Andrew Smith who will generate pit-free CHMs from high resolution #LiDAR‬  with over 40 pulses per square meter in an area with trees up to 70 meters in height. We at rapidlasso would love to take a look at that data. How many "partial CHMs" will he have to compute to eliminate all pits ...?
Andrew Smith (recipient of three LASmoons) Advanced Diploma in GIS Applications Vancouver Island University, Victoria, CANADA Background: Forestry and natural resource development are a large part ...
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More great news in response to +Esri proprietary "LAZ cloning" that is angering the #LiDAR  community that has enyoyed open point storage formats in the past. The Canton of Zürich has opened all of their 8 pulses/sqrmtr holdings. The points are stored in 7783 #LASzip‬  compressed ‪#‎LAZ‬ files totalling over 300 GB. You can download them via a simple and a fancy portal:
simple: http://maps.zh.ch/download/hoehen/2014/lidar/
fancy: http://maps.zh.ch/?topic=LidarZH&offlayers=dom2014hillshade
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LAStools

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As +LAStools has become very popular for #LiDAR  processing in forestry applications, #rapidlasso  has added more functionality to support plot- and raster-based operations like the new '-split' option in lasclip that gets all points from plots defined in a shapefile into separate files but also many new metrics in lascanopy. A particular interesting one are the 'bincentiles' that can be requested, for example, with '-b 10 30 50 80'. The two slides below (courtesy of David Herries from Interpine Group Ltd in Rotorua, NZ) explain what these bincentiles capture at the example of two different trees.
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Director +Patryk Kizny presents aesthetically pleasing #LiDAR  visuals in his latest short film “REBIRTH“. The 14 minute clip can be watched online. Turn on audio for narration and soundtrack. There is also a neat timelapse video about the “scanning of the temple” by ekg-baukultur.com who used a Faro system for the scan.
Director Patryk Kizny shows us - once more - aesthetically pleasing visuals in his latest short "REBIRTH". Already known for turning high-dynamic range (HDR) imagery captured in historic buildings ...
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As answer to our recent blog post showing that restricted access to national #LiDAR  holdings is overall more costly to governments than providing it as open data, Stefan Ziegler was tweeting "10 billion points can't be wrong" and that the latest LiDAR of Canton of Solothurn is now freely available for download: http://www.catais.org/geodaten/ch/so/kva/hoehen/2014/lidar/
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efficient tools for LiDAR processing
Introduction
LAStools are a collection of highly-efficient, scriptable tools (optional with GUI) for multi-core batching that process LAS, compressed LAZ, Terrasolid BIN, ESRI Shapefiles, and ASCII in an extremely fast manner:

* lasground.exe extracts bare-earth by classifying ground points
* lasclassify.exe find buildings and the trees above the ground
* lasgrid.exe rasters large LAS files into elevation/intensity grids
* lasboundary.exe extracts an enclosing polygon of the points
* lasheight.exe computes the height of each point above ground
* lasclip.exe clips points against building footprints / flight swaths
* lastile.exe tiles huge amounts of LAS points into square tiles
* txt2las.exe converts LiDAR from ASCII text to binary LAS
* las2txt.exe turns LAS into human-readable easy-to-parse ASCII
* lassplit.exe splits points of LAS files into flight lines
* and more ...

Our powerful, lossless LiDAR compressor laszip.exe turns large LAS files into much smaller LAZ files that are only 7 - 20 percent of the original file size.