JGribX

NOTE: Since commit 1f3fd1e (19th March 2020), the history of this repository has been rewritten to migrate binary files (.grb and .grb2) to Git LFS. Anyone checking out the repository should clone it again rather than pulling.

Introduction

JGribX is a GRIB decoder written in Java. It is essentially a fork of JGrib, which as far as I know is now no longer being actively developed. JGribX currently supports both GRIB-1 and GRIB-2 files.

The main objective of JGribX is to create an easy-to-use interface to extract data from GRIB files.

Improvements on JGrib

Here is a shortlist of the major changes made since JGrib (version 7 beta):

• supports GRIB-2 files
• supports grid definition values given as south latitude and west longitude
• looks up parameter information from locally stored Grib Parameter Tables (GPT) (instead of a single hardcoded GPT)
• validates each GRIB record
• skips invalid/unsupported GRIB records (showing the appropriate errors/warnings)

Dependencies

Requires JDK/JRE version 8 or above.

Important Notes

JGribX is still under active development and therefore contains a large amount of unsupported features and operations. These will be implemented gradually over time. If you would like certain features to be implemented or perhaps have found some issues, please open an issue containing all the relevant information.

Parameter Codes

To uniquely identify and represent different parameters, each parameter has been given its own code. A list of parameter codes can be viewed here.

Level Codes and LTVIDs

Similar to parameter codes, level codes are used to uniquely identify each level type and value(s). For example, an isobaric level is represented by the code ISBL. In addition, an isobaric level of 200 hPa is represented by the level type-value ID (LTVID) ISBL:200. A list of level codes can be viewed here.

Usage

JGribX was originally designed to be a Java library, meaning that it did not have any useful functionality when run as a standalone app. However, a command-line interface is currently being developed which allows JGribX to be used as a standalone app via command-line.

Building a Library

Ensure that you have a copy of Gradle

Run the following command at the terminal

gradle clean build

Library Interface

The simplistic library interface can be observed from the following code snippet (omitting extra stuff such as try-catches):

/* Get the temperature at an isobaric level of 200 hPa above Valletta, Malta at 6th November 2017 14:00:00 */

GribFile gribFile = new GribFile("filename.grb");   // typically .grb or .grb2 extension

Calendar forecastDate = new GregorianCalendar(2017, Calendar.NOVEMBER, 6, 14, 0, 0);
String parameterCode = "TMP";    // parameter code for temperature
String ltvid = "ISBL:200";       // LTVID (level type-value ID)
double latitude = 35.8985;       // latitude at point of interest
double longitude = 14.5133;      // longitude at point of interest

GribRecord record = gribFile.getRecord(forecastDate, parameterCode, ltvid);
double value = record.getValue(latitude, longitude);

Further examples on how to use JGribX can be found here.

Command-Line Interface

As of version 0.4, JGribX can also be used from command-line. For example, to get a quick summary of the contents of a GRIB file:

java -jar JGribX.jar -i path/to/file

Downloads

Binary builds (currently as JAR files), together with the source, can be found in the Releases page. As of v0.4, these JAR files can be used both as a library and as a standalone app (CLI). Previous versions can only be used as a library.