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Re: [thredds] Thredds opendap and HDF5 groups



Hi John,

We are considering using TDS for internal distribution of satellite data. We handle a variety of file formats (including HDF5 files with groups) so the Common Data Model abstraction and opendap serving is interesting.
The choice of client would be left to the users.

Best regards
Esben

John Caron wrote:
Hi Esban:

The big problem is that there are no groups in DAP 2.0, however they have been added to DAP 4.0. However DAP 4.0 is not yet officially released.

May I ask what client you want to use to read these HDF5 files? IDV or something else?

Esben Stigård Nielsen wrote:
Hi John,

Do you have an estimate when a TDS version with correct handling of groups in opendap will be released?

Best regards
Esben

John Caron wrote:
Hi Esben:

Yes, you are correct that the TDS opendap server is not correctly handling groups. We will get that onto our priority list to work on.

Esben Stigård Nielsen wrote:
Hi,

I'm attempting to set up Thredds 4.0 to serve HDF5 files through opendap. The HDF5 files contains 11 image groups 'image1' to 'image11'. In each group the data is contained in the variable 'image_data'.
As a test example I have added the following lines to catalog.xml:

 <datasetRoot path="msg/level2" location="/data/msg/level2" />
 <dataset name="Test MSG" ID="testMSG" serviceName="dapService"
  urlPath="msg/level2/level2_MSG2_8bit_VISIR_STD_20091005_0700.H5"
  dataType="Grid">
    <dataFormat>HDF5</dataFormat>
 </dataset>

Now the dds of the data URL returns:

Dataset {
    Float32 geo_ref_tiepoints[1][5041];
    Byte image_data[3712][3712];
    Byte image_preview[96][96];
    Int32 calibration_annotation_index[5];
    String calibration_annotation_table[5];
    Float32 calibration_table[256][2];
    Byte image_data[3712][3712];
    Int32 calibration_annotation_index[5];
    String calibration_annotation_table[5];
    Float32 calibration_table[256][2];
    Byte image_data[3712][3712];
    Int32 calibration_annotation_index[5];
    String calibration_annotation_table[5];
    Float32 calibration_table[256][2];
    Byte image_data[3712][3712];
    Int32 calibration_annotation_index[5];
    String calibration_annotation_table[5];
    Float32 calibration_table[256][2];
    Byte image_data[3712][3712];
    Int32 calibration_annotation_index[5];
    String calibration_annotation_table[5];
    Float32 calibration_table[256][2];
    Byte image_data[3712][3712];
    Int32 calibration_annotation_index[5];
    String calibration_annotation_table[5];
    Float32 calibration_table[256][2];
    Byte image_data[3712][3712];
    Int32 calibration_annotation_index[5];
    String calibration_annotation_table[5];
    Float32 calibration_table[256][2];
    Byte image_data[3712][3712];
    Int32 calibration_annotation_index[5];
    String calibration_annotation_table[5];
    Float32 calibration_table[256][2];
    Byte image_data[3712][3712];
    Int32 calibration_annotation_index[5];
    String calibration_annotation_table[5];
    Float32 calibration_table[256][2];
    Byte image_data[3712][3712];
    Int32 calibration_annotation_index[5];
    String calibration_annotation_table[5];
    Float32 calibration_table[256][2];
    Byte image_data[3712][3712];
    Int32 calibration_annotation_index[5];
    String calibration_annotation_table[5];
    Float32 calibration_table[256][2];
    Byte color_palette[256][3];
    Byte color_palette[256][3];
    Byte color_palette[256][3];
    Byte color_palette[256][3];
    Byte color_palette[256][3];
    Byte color_palette[256][3];
    Byte color_palette[256][3];
    Byte color_palette[256][3];
    Byte color_palette[256][3];
    Byte color_palette[256][3];
    Byte color_palette[256][3];
} msg/level2/level2_MSG2_8bit_VISIR_STD_20091005_0700.H5;

It seems all information regarding the HDF5 groups have been lost and I'm unable to distinguish between the different variables. Is it not possible to serve HDF5 with groups through opendap on TDS or have I missed something in the setup?

Best regards
Esben Nielsen

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