[netcdfgroup] Modeling LiDAR in NetCDF?

• To: netcdfgroup@xxxxxxxxxxxxxxxx
• Subject: [netcdfgroup] Modeling LiDAR in NetCDF?
• From: Timothy Lebo <lebot@xxxxxxx>
• Date: Mon, 3 Feb 2014 09:09:48 -0500

NetCDF,

How can (or should) LiDAR be modeled in NetCDF-4?

I’m a NetCDF novice, and it seems to me that the format assumes uniformly 
spaced samples (e.g. [1]).

I see from the archives that LiDAR isn’t a very popular topic on this list [2], 
but I figured I’d give it a shot and ask for any suggestion you may have.
Below is a table of sample points that I’d like to encode in NetCDF. It 
originates from a USGS LAS file about Disneyland.

lat lon alt intensity category(Ground=2;Low-Vegetation=3;Unclassified=1;Water=9)
414783.24 3741669.72 40.32 26 9
414782.09 3741669.31 40.44 3 9
414782.73 3741670.04 40.40 10 9
414782.03 3741670.63 40.28 26 9
414781.51 3741671.03 40.34 22 9

My latest attempt is at [3] and included below, but it isn’t satisfactory 
because I’m forced to round my points to suit a grid.
I was thinking that I should just assert a series of 1x1 dimensional records, 
but I’m not sure how I could group them in a sensible way.
Also, I get the sense that I’m losing the point of using NetCDF in the first 
place.

Any thoughts?

Thanks for your consideration.
Regards,
Tim Lebo


[1] 
http://www.unidata.ucar.edu/software/netcdf/workshops/2010/apis_examples/ExampleDataset2D.html
[2] http://bit.ly/1gGjsgs
[3] 
https://github.com/tetherless-world/opendap/blob/c566b40a97c6ce062a9a54f45607583eca34ad56/data/source/usgs-gov/earthexplorer/version/disneyland-2014-Jan-31/manual/CA_OrangeCo_2011_000402.sample.cdl



netcdf disneyland_lidar {

dimensions:
   latitude  = 5 ;
   longitude = 1 ;

variables:
   float latitude(latitude) ;
      latitude:units = "?" ;
   float longitude(longitude) ;
      longitude:units = "?" ;
   float altitude(latitude, longitude) ;
      altitude:units = "?" ;
   float intensity(latitude, longitude) ;
      intensity:units = "?" ;
   int category(latitude, longitude) ;

data:
   // This sets up the grid that we don't actually want to assume.
   // ERROR: We're rounding to get to a grid.
   latitude  = 414781.5, 414782, 414782.5, 414783, 414783.5 ; 
   // ERROR: We're squashing to get to a grid.
   longitude = 3741670 ; 

   altitude =
      40.32,
      40.44,
      40.40,
      40.28,
      40.34 ;

   intensity =
      26,
      3,
      10,
      26,
      22 ;

   category =
      9,
      9,
      9,
      9,
      9 ;
}

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  • Re: [netcdfgroup] Modeling LiDAR in NetCDF?
    • From: Chris Barker