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• 4/16/2009 4:53 PM alan wrote:
  Thanks for sharing the LIDAR data link.
  
  Just curious how the data is used?
  Looks like rough elevation contours.
  
  Regards
  Alan
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  1. 4/16/2009 4:59 PM atanas entchev wrote:
     Alan:
     
     I am not sure if you are asking about this particular dataset, or about LiDAR in general. You can find a lot of useful LiDAR information here:
     
     http://lidar.cr.usgs.gov/
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• 4/17/2009 4:25 PM miles wrote:
  Wow this is potentially fantastic for me! As an environmental noise analyst, I often have to model topography pretty exhaustively. Is LiDAR data precise enough for this kind of work? A five foot differential is pretty important for me..
  
  I'd research it myself but I have to go research ESRI's new FREE geocoding service ^_^
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  1. 4/17/2009 8:08 PM atanas entchev wrote:
     Miles:
     
     This response comes from the kind folks at the USGS in Sioux Falls, SD (thank you, Jason Stoker and Karl Heidemann!):
     ___________________
     
     Hunterdon: The metadata includes the general statement below. It appears that the vendor did not choose to publish the measured accuracy and the customer was satisfied with this.
     
     "The lidar data fully comply with FEMA guidance as published in Appendix A, April 2003 and National Standard for Spatial Accuracy (NSSDA). When compared to GPS survey grade points in generally flat non-vegetated areas, at least 95% of the positions have an error less than or equal to 36.3 cm (equivalent to root mean square error of 18.5 cm if errors were normally distributed)."
     _____________
     
     Somerset: This vendor was obviously very proud of the accuracy they achieved:
     
     Independent accuracy testing was performed by Dewberry using 60 high accuracy quality control checkpoints distributed around Somerset County on near level open bare terrain and near level vegetated terrain. Dewberry uses testing procedures consistent with those specified in the National Standard for Spatial Data Accuracy (NSSDA). RMSEz Bare Earth: 0.06m compared to the specified 0.15m for accuracy, and Vegetation: 0.10m compared to the specified 0.27m).
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     1. 4/18/2009 8:46 PM miles wrote:
        Great intel, thanks Atanas!! Less than 2 feet accuracy 0_0 At that resolution, I can't imagine how monstrous those rasters are..
        
        Even though they have no reason to, if only Google would someday invest in LiDAR instead of just showmanship, like buying the ocean floor nonsense or static bitmaps of terrain.
        
        Google Earth uses old space shuttle data right now!
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• 4/19/2009 2:06 PM atanas entchev wrote:
  Miles: Thanks are owed to Jason Stoker and Karl Heidemann from the USGS, who responded almost instantly to my inquiry resulting from your comment.
  
  Yeah, Google mapping (Maps and Earth) is more about the sizzle than it is about the steak.
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