GRIB2 library for Go programming language (golang)
History
Once upon time I had a need to read the GRIB2 file in golang. I used Google search and found the following libraries:
- https://github.com/analogic/grib - obsolete
- https://github.com/brockwood/gogrib2 - empty
- https://github.com/nilsmagnus/grib
Library nilsmagnus/grib
looked reassuringly. I downloaded gfs.t00z.pgrb2.0p25.f001 file from nomads.ncep.noaa.gov
, ran grib
export and got error format is not supported
(((.
I decided to develop GRIB2 library by myself. I looked at nilsmagnus/grib
and libraries for Java and Python. All libraries are attempts to understand how GRIB2 is arranged inside and to develop GRIB2 engine using appropriated programming language.
There was the reference GRIB2 implementation - wgrib2 tool. Look at wgrib2
source code. It's a lot of "crazy" C
language code ))). As for me it's very difficult to understand how it works in details. There was the way to call wgrib2
from golang application. But I rejected that due to the following reasons:
-
wgrib2
is not thread-safe. There are a lot of global read/write variables inside code. -
I prefer pure golang libraries
I saw the only one way - to port wgrib2
to golang. I did not want to repeat approach of another libraries. I was not going to rewrite wgrib2
to golang. I decided to port wgrib2
engine C
code to golang
with minimal correction and develop simple wrapper. I used results of wgrib2
export to CSV as the reference for testing. That approach allows:
- safe time (porting spent few days only)
- easy apply new features and patches from original
wgrib2
development stream
I used grib2-v2.0.6c
version. Here is the result of my work. The work is on final stage.
How-to
go get -u github.com/amsokol/go-grib2
It contains only one function that reads GRIB2 file:
func Read(data []byte) ([]GRIB2, error)
where GRIB2
is the structure with parsed data:
// GRIB2 is simplified GRIB2 file structure
type GRIB2 struct {
RefTime time.Time
VerfTime time.Time
Name string
Description string
Unit string
Level string
Values []Value
}
// Value is data item of GRIB2 file
type Value struct {
Longitude float64
Latitude float64
Value float32
}
Unlike wgrib2
It's thread-safe.
See the following usage examples:
- file-grib2csv - export GRIB2 file to CSV
- http-grib2csv - export
nomads.ncep.noaa.gov
HTTP response to CSV
Roadmap
Major work is finished. go-grib2
is ready to use. I have a little bit to port:
- parse
longitude
andlatitude
are stored asgauss
,space_view
,irr_grid
- parse data are stored using
complex
andrun_length
algorithms
Issues
go-grib2
does not support jpeg
, png
and aec
data package formats. The reason is wgrib2
uses external C
libraries to read these formats. If you have an idea how to easy port jpeg
, png
and aec
please let me know.
Need help
I need help is testing. Please test go-grib2
with several GRIB2 files from several providers. Use wgrib2
CSV export to validate results. Please create issues here.