[gdal-dev] vsicurl and --range byte-range

[Joaquim Manuel Freire Luís]

Fantastic Even. Thanks a lot.
(and ofc I meant to say grib2, not “gring2”)

Joaquim

From: Even Rouault <even.rouault at spatialys.com>
Sent: Thursday, May 8, 2025 11:04 PM
To: Joaquim Manuel Freire Luís <jluis at ualg.pt>; gdal-dev at lists.osgeo.org
Subject: Re: [gdal-dev] vsicurl and --range byte-range


Joaquim,

You can combine /vsisubfile/  (https://gdal.org/en/stable/user/virtual_file_systems.html#vsisubfile-portions-of-files) and /vsicurl/

/vsisubfile/${offset}_${length}/vsicurl/${url}

e.g.

$ gdalinfo /vsisubfile/802533_508958,/vsicurl/https://ecmwf-forecasts.s3.eu-central-1.amazonaws.com/20240301/00z/ifs/0p25/oper/20240301000000-24h-oper-fc.grib2 --debug on

[...]
Band 1 Block=1440x1 Type=Float64, ColorInterp=Undefined
  Description = 92500[Pa] ISBL="Isobaric surface"
  Metadata:
    GRIB_UNIT=[%]
    GRIB_COMMENT=Relative humidity [%]
    GRIB_ELEMENT=RH
    GRIB_SHORT_NAME=92500-ISBL
    GRIB_REF_TIME=1709251200
    GRIB_VALID_TIME=1709337600
    GRIB_FORECAST_SECONDS=86400
    GRIB_DISCIPLINE=0(Meteorological)
    GRIB_IDS=CENTER=98(ECMWF) SUBCENTER=0 MASTER_TABLE=27 LOCAL_TABLE=0 SIGNF_REF_TIME=1(Start_of_Forecast) REF_TIME=2024-03-01T00:00:00Z PROD_STATUS=0(Operational) TYPE=1(Forecast)
    GRIB_PDS_PDTN=0
    GRIB_PDS_TEMPLATE_NUMBERS=1 1 2 255 154 0 0 0 1 0 0 0 24 100 0 0 1 105 84 255 255 255 255 255 255
    GRIB_PDS_TEMPLATE_ASSEMBLED_VALUES=1 1 2 255 154 0 0 1 24 100 0 92500 255 -127 -2147483647

Even
Le 08/05/2025 à 23:48, Joaquim Manuel Freire Luís via gdal-dev a écrit :
Hi,

I’m writing a tool to download ECMWF forecast data in gring2 format. But since those files have > 150 bands and most of times I’m only interested in a couple of them, I’m using the only documented mechanism that I found [1], which is the “curl –range start-stop”. That works fine but what I would really like is to be able to use

gdal_translate /vsicurl/…

because then I should be able to save the result directly in netCDF and even get only a sub-region. But I’m not able to find a way to use both /vsicurl/ and a (equivalent) –range option. Is that possible and I didn’t find how to, or we simple cannot do it?

Thanks

Joaquim

[1] https://confluence.ecmwf.int/display/DAC/ECMWF+open+data%3A+real-time+forecasts+from+IFS+and+AIFS#ECMWFopendata:realtimeforecastsfromIFSandAIFS-DownloadASingleFieldWithWget



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