There is documentation missing for snappy. That’s true.
As snappy is just a bridge into the Java API it is good to know the Java API. See SNAP API.
We have ideas on how to improve this situation but the realisation needs some more time.
Beside the guides I mentioned already above, there examples linked in the tutorial page. See External Resources section.
Another way of finding examples is to search this forum for GPF.createProduct
That’s the right way to store the data. You can also choose between different output formats. You have tried already GeoTIFF.
As a hint, you don’t need to write the data of the intermediate results. You can directly provide the result of one operator as input to the next operator.
Regarding the visualisation. There is a recent thread about it.
The actual data of band can be retrieved by:
import numpy as np
band = product.getBand(Sigma0_VV')
w = band.getRasterWidth()
h = band.getRasterHeight()
data = np.zeros(w*h, dtype=np.float32)
# this is the full image
band.readPixels(0, 0, w, h, data)
# Now you have the data in the numpy array 'data' and you can use it with e.g. matplotlib for visualisation