README.md

grib2-simple

grib2-simple is a tiny node.js library to parse the content of grib2 files. It is implemented in plain JavaScript (and thus is not a wrapper for a C library or Java program).

grib2-simple is being developed as part of the Designetz project and only covers the functionality that is needed to parse grib2 files provided by the open data project of DWD (Deutscher Wetter Dienst). There are currently no plans to extend the library to cover the full functionality of grib2 files. This might change in the future, though.

License

See the LICENSE file for license rights and limitations (MIT).

Install

npm install grib2-simple

Usage

The grib2-simple project exposes a single function which parses the content of a grib2 file given as a Buffer. The result given is Array of objects as follows

[
  {
    referenceTimestamp: <<Integer>>, // the reference time as UNIX timestamp in ms,
    forecastTimestamp: <<1500001000000>>, // the forecast time as UNIX timestamp in ms,
    getValue: function(lon, lat) {...}, // a function to retrieve a value
    sections: <<Object>> // an object that contains the information of the sections
  },
  ...
]

Each Array element represents a grib2 record, whereby a grib2 file contains one or more grib2 records.

The function getValue is used to retrieve a value for given longitude and latitude in °.

Example

const grib2 = require('./index')
const fs = require('fs-extra')

async function test() {

    // load file content
  const fileContentBuffer = await fs.readFile('./sample_data/COSMODE_single_level_elements_PS_2018020500_000.grib2')

  // parse file content (this is a synchronous operation)
  // the result is an array, as multiple grib2 files can be concatenated to a single
  const grib2Array = grib2(fileContentBuffer)

  // get value at predefined coordinate
  // first parameter is longitude (East is positiv, West is negative)
  // second parameter is latitude (North is positive, South is negative)
  const value = grib2Array[0].getValue(7.13, 48.628)
  
  console.log("Reference time: " + grib2Array[0].referenceTimestamp)
  console.log("Forecast time: " + grib2Array[0].forecastTimestamp)
  console.log("Value at longitude 48.628 °N and 7.13 °E: " + value)
}

test()