Hi Stephen, I sounds like you should be asking on https://groups.google.com/a/hycom.org/forum/#!forum/forum rather than gdal-dev.
-kurt On Sun, Jun 5, 2016 at 2:10 PM, Stephen Woodbridge <[email protected]> wrote: > Hi Even, Kurt, > > Thank you for the suggestions. > > I'm reading through stuff and searching for solutions. I need access to > the 2d layer which is only available via the GLBa0.08 dataset and not in > the GLBu0.08 dataset which is easier to deal with. I'll start with the > GLBu0.08 dataset for the other data following Kurt suggestions. > > This page describes the problem of georeferencing the GLBa0.08 dataset but > the solution is based on windows python script and using ArcGIS, but the > idea might be adapted to writing some C/C++ or script to handle creating > those artifacts. I want to script the download and processing of the data > into geotiff's running on Linux. > > http://code.nicholas.duke.edu/projects/mget/wiki/HYCOM > > One problem is that the HYCOM site does not have *.grid.[ab] files that I > can find. They are supposed to be in the topo directory: > > Index of ftp://ftp.hycom.org/datasets/GLBa0.08/expt_91.2/topo/ > > Name Size Last Modified > depth_GLBa0.08_09.a 57984 KB 8/24/2013 12:00:00 AM > depth_GLBa0.08_09.b 1 KB 8/24/2013 12:00:00 AM > depth_GLBa0.08_09.nc 173950 KB 11/12/2013 12:00:00 AM > > and it is not obvious how to read and incorporate these files as I think > they only work with the HYCOM related executables. > > I did notice the the lat/lon info is already in the .nc for the "u" > dataset which can be seen with ncdump. In fact it is also there for the "a" > dataset also, but the values 1-3298 and 1-4500 which is the size of the > file in pixels, so not helpful. > > I've looked on the HYCOM forum but that has not been very helpful yet. > > Thanks, > -Steve > > > On 6/5/2016 2:04 PM, Kurt Schwehr wrote: > >> Stephen, >> >> Take a look at these two discussions for starters on working with >> hycom: >> >> >> http://gis.stackexchange.com/questions/167155/how-can-i-make-geotiffs-of-individual-depth-layers-in-the-hycom-ocean-circulatio >> >> >> >> http://gis.stackexchange.com/questions/170882/how-can-a-make-a-netcdf-with-subgroups-smaller >> >> You should start with the regular grids. e.g. >> >> >> ftp://ftp.hycom.org/datasets/GLBu0.08/expt_91.1/data/hindcasts/2015/hycom_glb_911_2015093000_t000_uv3z.nc >> >> Make an 80 layer geotiff from the u/v and then use mapserver as >> Even suggested. >> >> -kurt >> >> >> On Sat, Jun 4, 2016 at 6:29 AM, Even Rouault >> <[email protected] <mailto:[email protected]>> >> >> wrote: >> >> Hi, >> >>> >>> 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? >>> >> >> gdaldem color-relief can output to a VRT, but given that this netCDF >> file is georeferenced through a geolocation array, you'll likely have >> first to run gdalwarp -geoloc to have something useful at the end. >> >> >>> 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. >>> >> >> See http://mapserver.org/input/vector/vector_field.html >> >> You don't need to create a vector file. >> >> You'll have to preprocess your file to get the u and v bands in the >> same raster. >> >> Even >> >> -- Spatialys - Geospatial professional services >> http://www.spatialys.com >> _______________________________________________ gdal-dev mailing >> list [email protected] <mailto:[email protected]> >> http://lists.osgeo.org/mailman/listinfo/gdal-dev >> >> >> >> >> -- -- http://schwehr.org >> > > > --- > This email has been checked for viruses by Avast antivirus software. > https://www.avast.com/antivirus > > -- -- http://schwehr.org
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