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fimex:faq [2013-02-08 11:37:45] heikok |
fimex:faq [2024-07-03 07:11:55] (current) alexanderb opendap auth on jammy |
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====== Frequently Asked Questions ====== | ====== Frequently Asked Questions ====== | ||
+ | |||
+ | ===== Does fimex use file-locks for reading/ | ||
+ | |||
+ | It is very common, that NWP (numerical weather prediction) files are updated while the model is running. It is often desirable to be able to read the file already when the model is still running, e.g. to see the first few ours of weather prediction. | ||
+ | |||
+ | * Fimex does not use file-locks for reading: Graphical interfaces like [[http:// | ||
+ | * Fimex does not implement file-locking for writers generally, though in particularly with the [[http:// | ||
+ | |||
+ | |||
+ | ===== How can I change the units of a variable? ===== | ||
+ | |||
+ | If the original variable e.g. '' | ||
+ | |||
+ | If the input-file has the wrong units, e.g. Celsius while the data in fact is Kelvin, you should use the input.config=... and re-define the units-attribute. The data-values won't be changed. | ||
+ | |||
===== How to solve problems with a short variable? ===== | ===== How to solve problems with a short variable? ===== | ||
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</ | </ | ||
In this example, the precipitation will be described with an accuracy of 0.1mm and up to 3276.7mm. The ncml-configfile will be applied right before writing with the '' | In this example, the precipitation will be described with an accuracy of 0.1mm and up to 3276.7mm. The ncml-configfile will be applied right before writing with the '' | ||
+ | |||
+ | ===== Vector-rotation ===== | ||
+ | |||
+ | ==== Which vectors are auto-detected for rotation ==== | ||
+ | |||
+ | Vectors are autorotated if one of the following applies: | ||
+ | |||
+ | * the ''< | ||
+ | * the vector has a known CF-standard-name, | ||
+ | * x_wind, y_wind | ||
+ | * *_x_velocity, | ||
+ | * *_x_transport, | ||
+ | * *_x_displacement, | ||
+ | * *_eastward_*, | ||
+ | * the complete list can be found in the sources after '' | ||
+ | |||
+ | ==== Vector-rotation gives error-message (>= 0.48) and wrong values due to different units ==== | ||
+ | |||
+ | When rotating vectors for spatial interpolations, | ||
+ | |||
+ | A solution is to configure the vector to have the same scale/ | ||
+ | |||
+ | < | ||
+ | < | ||
+ | < | ||
+ | < | ||
+ | <remove name=" | ||
+ | < | ||
+ | </ | ||
+ | |||
+ | < | ||
+ | < | ||
+ | < | ||
+ | <remove name=" | ||
+ | < | ||
+ | </ | ||
+ | </ | ||
+ | |||
===== What does this error-message mean? ===== | ===== What does this error-message mean? ===== | ||
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</ | </ | ||
+ | === OpENDAP and slicing === | ||
+ | OpENDAP servers are often limited on how much data can be read at per request, e.g. thredds allows only 500MB binary data / 50MB ascii data per request before failing with an error like | ||
+ | < | ||
+ | syntax error, unexpected WORD_STRING, | ||
+ | context: Error { code = 403; message = " | ||
+ | terminate called after throwing an instance of ' | ||
+ | what(): | ||
+ | Aborted | ||
+ | </ | ||
- | ===== Why takes linking with '' | + | Fimex tries to subdevide requests into one unlimited slice per variable. Unfortunately, |
+ | < | ||
+ | <?xml version=" | ||
+ | <netcdf xmlns=" | ||
+ | xmlns: | ||
+ | xsi: | ||
+ | < | ||
+ | </ | ||
+ | </ | ||
- | This happens with older versions of gcc, seen with 3.3 on debian sarge. | ||
- | Use '' | + | ==== Authentication ==== |
+ | |||
+ | In theory, it should be possible to specify username and password | ||
+ | - in '' | ||
+ | - as part of the URL for example | ||
+ | |||
+ | Example '' | ||
+ | < | ||
+ | machine thredds.met.no | ||
+ | login XXXX | ||
+ | password YYYY | ||
+ | </ | ||
+ | |||
+ | Example '' | ||
+ | < | ||
+ | HTTP.NETRC=YOURHOME/ | ||
+ | |||
+ | HTTP.CREDENTIALS.USERNAME=XXXX | ||
+ | HTTP.CREDENTIALS.PASSWORD=YYYY | ||
+ | |||
+ | HTTP.USERNAME=XXXX | ||
+ | HTTP.PASSWORD=YYYY | ||
+ | </ | ||
+ | |||
+ | Unfortunately, this does not always seem to work as expected. | ||
+ | Known status of OpenDAP authentication support (applies to '' | ||
+ | * Specifying | ||
+ | * For Ubuntu 16.04 (xenial, EOL), both URL and netrc seem to work. | ||
+ | * For Ubuntu 18.04 (bionic), username and password cannot be read from netrc, but can be specified in the URL. | ||
+ | * For Ubuntu 20.04 (focal), username and password can only be read from netrc, but cannot be specified in the URL. | ||
+ | * For Ubuntu 22.04 (jammy), the only solution known to us is to add a '' | ||