[gdal-dev] Questions on working with HYCOM data in netcdf format

[Stephen Woodbridge]

Hi All,

I want to convert some HYCOM data into GTiff format and I'm a little 
lost on how to get started, whether I can do what I need just using a 
vrt or if I'm going to have to write code to process the data.

To start with I have placed gdalinfo on one file here:
http://imaptools.com:8080/dl/hycom-gdalinfo.txt

The data comes from http://hycom.org/dataserver/glb-analysis
and I will need to be using GLBa0.08 dataset.

I have two use cases:

1) The simple one is to extract say Band 1 into a georeferenced GTiff 
and apply color to using color ranges without loosing the NODATA. I 
think I can do later using .vrt, correct?

I'm not sure how to deal with the georeferencing, because the download 
site says: "Native hycom .[ab] data converted to NetCDF on native 
Mercator-curvilinear HYCOM horizontal grid" but that does not seem in 
sync with the Metadata in the file.

2) The more complicated case is that there are two files:
    a)  eastward_sea_water_velocity (aka: u, u-velocity)
    b)  northward_sea_water_velocity (aka: v, v-velocity)
that I would like to use to create a grid of vectors with arrowheads 
using u and v to define the vector and where the color of the vector is 
related to the magnitude of its length. Ultimately this data will get 
rendered via mapserver so I'm wondering if I can do this via a GTiff or 
if I will have to resort to creating a massive point shapefile with 
attributes of angle and magnitude and use a symbol. It seems like it 
would be best if I can keep the data as a GTiff and then sample the 
points and render the vectors on the fly for when you zoom in/out.

Interesting data and I'm really pleased to see gdal can access it! Kudos 
on that.

Any guidance would be greatly appreciated.

Thanks,
   -Steve

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