CODEWITHSUNDEEP
pythonhdf5h5py
rickjarzy
rickjarzy

Reputation: 1

How can I define the spatial reference system for an hdf5 stack in python?

I'm new to h5py and my actual task is to create a hdf5-stack with MODIS subsets. I can create the stack with all the nice data in it but I'm not able to create or attach a spatial reference system. Goal is to load single datasets from the stack into a viewer like in ArcGIS and it should be placed at its right position.

How do I give the stack the right spatial/projection information?

Upvotes: 0

Views: 987

Answers (1)

Yossarian
Yossarian

Reputation: 5471

You can attach spatial coordinates to an HDF5 dataset with dimension scales - these are simply other datasets that are associated with your first dataset. If you want to indicate that a particular dimension has certain physical units you can label the dimension, which is done using the HDF5 dimension scale API: H5DSset_label().

Dimension scales are possible in h5py, using h5py.dims.create_scale() and h5py.dims.attach_scale(), and h5py.dims.label to set the label.

For example, to attach two datasets to foo.h5:/data to specify the latitude and longitude, and that they are in degrees, you can first set their labels as follows (with f being the HDF5 file):

f['data'].dims[0].label = 'degrees'
f['data'].dims[1].label = 'degrees'

Then to actually add the coordinates, you first need to create a scale, then attach the dataset (where f['phi'] is a pre-existing dataset with your coordinates in):

f['data'].dims.create_scale(f['phi'], 'latitude')
f['data'].dims[1].attach_scale(f['phi'])

You can then access the labels with

[dim.label for dim in f['data'].dims]

and the dimension scales themselves with

f['data'].dims[1][0]

or

f['data'].dims[1]['latitude']

Upvotes: 1

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