hvPlot Tap stream with background map not working

hvPlot
1

I recreated the example of an xarray map and time-series plot that was posted in https://discourse.holoviz.org/t/simple-panel-example-of-map-time-series-interaction-for-data-cube/1485.

It is quite amazing to see how much can be achieved with only a few lines of code. The code allows me to tap on map cells and receive a time-series for the selected cell.

The example works very well when some lines defining a background map are commented out, as can be seen below:

import panel as pn
import xarray as xr
import holoviews as hv
import hvplot.xarray
import cartopy.crs as ccrs

pn.extension()

ds = xr.tutorial.open_dataset('air_temperature')

image, select = ds.hvplot('lon', 'lat', widgets={'time':pn.widgets.DiscreteSlider},
                          alpha = 0.6,
                          frame_width = 500,
                          geo = True)#,
                          #tiles = 'CartoLight',
                          #crs = ccrs.PlateCarree(),
                          #projection = ccrs.PlateCarree(),
                          #project = True,
                          #coastline = '110m')
                    
stream = hv.streams.Tap(source = image.object, x = 50, y = 240)

def timeseries(x, y):
    return ds.sel(lon=x, lat=y, method='nearest').hvplot('time', frame_width = 500)

pn.Row(pn.Column(image, select), pn.bind(timeseries, x=stream.param.x, y=stream.param.y))

working_example
working_example1556×721 72.3 KB

However, it would be great to add a background map for better orientation. But whenever I uncomment the lines in the above code, the tap function stops working.

Does anyone know why? Maybe it has something to do with the projection?

Thank you in advance!

2

My guess is if you print(x, y) in timeseries, you’ll probably notice that x/y are no longer in degrees. You need to reproject those points to degrees. https://scitools.org.uk/cartopy/docs/latest/crs/index.html#cartopy.crs.CRS.transform_point

1 Like
3

Thanks for your advice!
I added print(x, y) and checked the response in the command prompt (I also checked with a similar project that uses different data).
Without background map, the coordinates are printed in the prompt. With background map, I don’t get any response.

4

Probably related to the fact that once you turn on a background map, it becomes a gv.Overlay.

5

Yes same issue as this. Would suggest leaving off the tile source for now, attaching the stream, and then manually overlaying it on a tile source imported from gv.tile_sources.

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6

@timsta95 I got the same problem as you. I found in current situation the hv.streams.Tap need a source setting of geoviews object. But when you use a coastline, the image became a overlay object. When I set the source as image.Image.I (stream = hv.streams.Tap(source = image.Image.I, x = 50, y = 240)
), it works fine.

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