Adam,
OPeNDAP is a tool for remote data access that allows you to access portions
of a dataset/file without the need to download the entire thing. Given
that, I'm not sure there's any need for you to install Tomcat and run your
own THREDDS server. For accessing the data from THREDDS using OPeNDAP, all
you need are:
- siphon
- netcdf4-python
The siphon examples you mentioned use CDMRemote (cdmr) access only because
that's built into siphon itself. To access the Level 3 NEXRAD products
using OPeNDAP, this should suffice, where we're replacing the `Dataset`
class pulled from `siphon.cdmr` with one pulled from `netCDF4`. Here's a
complete example:
from datetime import datetime
import matplotlib.pyplot as plt
import numpy as np
from netCDF4 import Dataset
from siphon.radarserver import RadarServer, get_radarserver_datasets
ds = get_radarserver_datasets('http://thredds.ucar.edu/thredds/')
url = ds['NEXRAD Level III Radar from IDD'].follow().catalog_url
rs = RadarServer(url)
query = rs.query()
query.stations('FTG').time(datetime.utcnow()).variables('N0Q')
catalog = rs.get_catalog(query)
ds = list(catalog.datasets.values())[0]
data = Dataset(ds.access_urls['OPENDAP'])
rng = data.variables['gate'][:] / 1000.
az = data.variables['azimuth'][:]
ref = data.variables['BaseReflectivityDR'][:]
x = rng * np.sin(np.deg2rad(az))[:, None]
y = rng * np.cos(np.deg2rad(az))[:, None]
ref = np.ma.array(ref, mask=np.isnan(ref))
fig, ax = plt.subplots(1, 1, figsize=(9, 8))
ax.pcolormesh(x, y, ref)
ax.set_aspect('equal', 'datalim')
ax.set_xlim(-460, 460)
ax.set_ylim(-460, 460)
plt.show()
Ryan
On Thu, Feb 23, 2017 at 10:24 AM, Lampl, Adam <alampl@xxxxxxxxxx> wrote:
> Hello ,
> I am looking at your siphon example to access level 3 data. For the online
> example it uses cdmr access. I see that created is a directory of scripts
> for cdmr. Is it possible for me to access using OPENDaP access through
> siphon? or would i have to create a bunch of scripts to do so like you do
> for cdmr? Also what is the advantage of downloading tomcat for what I am
> trying to do. Having some difficulty getting it to open thredds.war
> properly.
> I am a student at the University at Albany interning for the Atmospheric
> Science Research Center just trying to broaden my knowledge of data science
> and working with a jupyter notebook. Any advice would mean a lot!
> Thanks in advance,
> Adam Lampl
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--
Ryan May, Ph.D.
Software Engineer
UCAR/Unidata
Boulder, CO
