Hi All,
I have a program that produces netCDF files of water levels over a geographic
region fro different times.
the header looks like this:
===============================================
lon = 720 ;
lat = 330 ;
grid_lon = 720 ;
grid_lat = 330 ;
rows = 3 ;
clms = 3 ;
time = UNLIMITED ; // (226 currently)
variables:
double lon(lon) ;
lon:long_name = "longitude" ;
lon:units = "degrees_east" ;
lon:point_spacing = "even" ;
double lat(lat) ;
lat:long_name = "latitude" ;
lat:units = "degrees_north" ;
lat:point_spacing = "uneven" ;
double grid_lon(grid_lon) ;
grid_lon:long_name = "longitude" ;
grid_lon:units = "degrees_east" ;
grid_lon:point_spacing = "even" ;
double grid_lat(grid_lat) ;
grid_lat:long_name = "latitude" ;
grid_lat:units = "degrees_north" ;
grid_lat:point_spacing = "uneven" ;
double O2Geo(clms, rows) ;
O2Geo:long_name = "rotation matrix" ;
float max_amp(grid_lat, grid_lon) ;
max_amp:long_name = "Maximum Wave Amplitude" ;
max_amp:units = "centimeters" ;
max_amp:_FillValue = -1.e+34f ;
max_amp:missing_value = -1.e+34f ;
double time(time) ;
time:long_name = "time" ;
time:units = "seconds" ;
time:calendar = "gregorian" ;
float ha(time, lat, lon) ;
ha:long_name = "Wave Amplitude" ;
ha:units = "centimeters" ;
ha:missing_value = -1.e+34f ;
ha:_FillValue = -1.e+34f ;
===============================================
i would like to extract a time series of data at a specific location.
I have been looking at the ncdump command and thinking there would be a way do
it at the command line, i.e. something like:
ncdump -v ha(lat,lon, time[1=>t]) datafile.nc > timeseries.cdl
(I realize the syntax is totally wrong, i am just trying to express how I would
specify a lat/lon and ask for the data over the entire time)
then using ncgen to make a new binary netCDF that can be read by GMT's nc2xy
and output a simple 2 column time series.
but I don't think I can specify things that way with ncdump.
I then looked in to using the ncBrowse software. I have managed to use that to
specify a time series of data at a point, and even write that data out to a CDL
file. However, the file generated by ncBrowse (pasted below in an edited form)
cannot be read by nc2xy and has characters that are not compatible with ncgen
nc2xy tells me: nc2xy: NetCDF: Unknown file format [ha.cdl]
and ncgen tells me:
ncgen: ha.cdl line 7: syntax error, unexpected '=', expecting ',' or ')'
===================================================
netcdf ha.cdl {
dimensions:
time = UNLIMITED ; // (226 currently)
lat = 1 ;
lon = 1 ;
variables:
double time(time=226);
time:long_name = "time";
time:units = "seconds";
time:calendar = "gregorian";
double lat(lat=330);
lat:long_name = "latitude";
lat:units = "degrees_north";
lat:point_spacing = "uneven";
double lon(lon=720);
lon:long_name = "longitude";
lon:units = "degrees_east";
lon:point_spacing = "even";
float ha(time=226, lat=330, lon=720);
ha:long_name = "Wave Amplitude";
ha:units = "centimeters";
ha:missing_value = -1.0E34f; // float
ha:_FillValue = -1.0E34f; // float
data:
time = 0.0, <ALL THE TIMES>, 14400.0 ;
lat = 24.00833 ;
lon = 60.00833 ;
ha = 1.0723767, <ALL THE ha VALUES>1.6242466 ;
}
===================================================
so then, I go in to the ha.cdl file and edit the header in a text editor to
remove the =226, =330 and =720 bits and change the line:
float ha(time=226, lat=330, lon=720);
to
float ha(time);
I then run run:
ncgen -b -o ha.nc ha.cdl
and make a file ha.nc which then can be accessed by nc2xy through the command:
nc2xy ha.nc -Ftime/ha > ha.txt
to create the file ha.txt which looks like:
===========================
0.000 17.423
64.000 61.289
128.000 36.575
<...SNIP...>
14336.000 -2.210
14400.000 -2.147
===========================
and is exactly what i want! Two columns, time and ha at that particular lat/lon
So I know it is possible...
So, if you are still with me, how can i do this more simply, through the
command line preferably, or even a small script that goes:
ncdump (args)
ncgen (args)
nc2xy (args)
would be fine, but I just need to know the right arguments to make it all talk
to each other.
if you can help me, MANY, MANY, THANKS!!!!
-jose
(p.s. i used to do this with MATLAB, but I recently had my computer with MATLAB
die, and i can't get it up and running again, so i am trying to do this an
alternative way...)
