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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
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On Mon, Feb 3, 2014 at 6:09 AM, Timothy Lebo <lebot@xxxxxxx> wrote: > How can (or should) LiDAR be modeled in NetCDF-4? > NetCDF is very flexible -- if you want to know how best to represent particular data in a standard way, you'll want o use a defined standard. Most commonly used is the "CF" metadata standard (CF for Climate Forecast, but is has been expanded and adopted for all sorts of other things): http://cf-pcmdi.llnl.gov/ A quick search of the standard name table does not turn up "lidar", but I'd be really surprised if it hadn't been used for that, so I'd puruse teh standard and see what matches your data well. > I’m a NetCDF novice, and it seems to me that the format assumes uniformly > spaced samples (e.g. [1]). > NetCDDF works really well for regular gridded data, but it by no means is restricted to that. You certainly dont want to arbitrarily shift your data points to a regular grid. 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 > if I"m reading this right, you have a whole bunch of points, each with a lat-lon, and a couple values and a flag associated with that. If there is no particular structure to the arrangement of the point, then you want to keep it as unstructured data: a bunch of 1-d arrays, length-number-of-points long: latitude longitude alt intensity catagory it's pretty much that simple, but browse through the CF standard to see how you want to label then and what mets-data to apply so that users will be most easily able to interpret the data. I think you want to look at what CF calls "Discrete Sampling Geometries". If it's unclear what do do a post to the CF list would probably result in good advice: http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > 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. > yeah, you really don't want to do that... -Chris -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception Chris.Barker@xxxxxxxx
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