Holoviews/Datashaded map overlay not displaying

Solution 1:

According to the holoviews docs, hv.rasterize is a high-level resampling interface and passes parameters to several internal methods:

holoviews.core.operation.Operation: group, input_ranges

holoviews.operation.datashader.LinkableOperation: link_inputs

holoviews.operation.datashader.ResamplingOperation: dynamic, streams, expand, height, width, x_range, y_range, x_sampling, y_sampling, target, element_type, precompute

holoviews.operation.datashader.AggregationOperation: vdim_prefix

Based on this, it looks like your arguments x_sampling and y_sampling are passed to ResamplingOperation, which are described:

x_sampling = param.Number(allow_None=True, inclusive_bounds=(True, True), label=’X sampling’)
Specifies the smallest allowed sampling interval along the x axis.

y_sampling = param.Number(allow_None=True, inclusive_bounds=(True, True), label=’Y sampling’)
Specifies the smallest allowed sampling interval along the y axis.

So, I'd guess that the issue is that providing the arguments x_sampling=1, y_sampling=1 to rasterize has the effect of aggregating all of your data to 1 degree, or approximately 110 km/70 mile blocks, which is causing the blockiness in your figure. Changing these parameters to a smaller value, such as 0.1 or smaller, should resolve the issue, as long as your data itself has sufficient resolution.