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fimex:faq [2012-04-17 10:58:52] heikok |
fimex:faq [2017-01-26 13:03:52] heikok [How to use fimex as opendap-client?] |
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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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The config-file for felt-files must at least define 1 existing parameter in the corresponding felt-file. Update your config-file (e.g. felt2nc_variables.xml) with the output from the felt-index, which can be read by felt-tools like '' | The config-file for felt-files must at least define 1 existing parameter in the corresponding felt-file. Update your config-file (e.g. felt2nc_variables.xml) with the output from the felt-index, which can be read by felt-tools like '' | ||
+ | ==== CDMException: | ||
+ | |||
+ | This error-message is unfortuneatly very misleading. In many cases, the '' | ||
+ | |||
+ | ===== How can I read grib-message which are split over several files? ===== | ||
+ | |||
+ | since fimex 0.40.1, it is possible to give multiple optional file-sources: | ||
+ | < | ||
+ | fimex --input.file=/ | ||
+ | --input.type=grb --input.config=/ | ||
+ | --input.optional=/ | ||
+ | --input.optional=/ | ||
+ | --output.file=eceps.nc4 | ||
+ | </ | ||
===== How to use fimex as opendap-client? | ===== How to use fimex as opendap-client? | ||
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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 | ||
+ | </ | ||
+ | |||
+ | Fimex tries to subdevide requests into one unlimited slice per variable. Unfortunately, | ||
+ | < | ||
+ | <?xml version=" | ||
+ | <netcdf xmlns=" | ||
+ | xmlns: | ||
+ | xsi: | ||
+ | < | ||
+ | </ | ||
+ | </ | ||
+ | |||
+ | |||
+ | ==== Authentication ==== | ||
+ | |||
+ | Authentication to opendap servers need to be configured by setup files. Generally, authentication is described in http:// | ||
+ | |||
+ | === Example === | ||
+ | |||
+ | Authentication to the NASA data available to earthdata users https:// | ||
+ | |||
+ | * Register a user, get a password and enable the needed application on the earthdata web-pages. Follow the instructions on their pages. | ||
+ | * Make sure you can access the desired data from your browser, e.g. by selecting a small opendap-ASCII dataset. | ||
+ | * Put the username/ | ||
+ | * '' | ||
+ | login XXXX | ||
+ | password YYYY</ | ||
+ | * make sure the file is only readable by you < | ||
+ | * allow fimex/ | ||
+ | * '' | ||
+ | HTTP.NETRC=/ | ||
+ | * test with an inventory of a opendap file < | ||
+ | * test with fimex < | ||
- | ===== Why takes linking with '' | ||
- | This happens with older versions of gcc, seen with 3.3 on debian sarge. | ||
- | Use '' | ||