💫 From dhdt_plot to IceSat2Explorer, an improved dashboard

Improve our HvPlot/Panel dashboard with some new bells and whistles! Like a proper GIS desktop tool, the xy_dhdt dashboard plot can now keep the zoom level when changing between variables (thanks to https://discourse.holoviz.org/t/keep-zoom-level-when-changing-between-variables-in-a-scatter-plot)! Supersedes e4874b0. This is a major refresh of my old IceSatExplorer code at https://github.com/weiji14/cryospheric-data-lakes/blob/master/code/scripts/h5_to_np_icesat.ipynb, which uses ICESat-1 instead of ICESat-2. The dashboard also takes a lot of cues from the example at https://examples.pyviz.org/datashader_dashboard/dashboard.html, implemented in holoviz/datashader#676.

Other significant improvements include a categorical colourmap for the 'referencegroundtrack' variable, and being able to see the height and time of an ICESat-2 measurement at a particular cycle on hover over the points! Oh, and did I mention that the rendering now happens on the GPU?!! Data transformed to and from Parquet is fast! Note that this is a work in progress, and that there are more sweeping improvements to come. I've also split out the crossover analysis code into a separate atlxi_lake.ipynb file since atlxi_dhdt.ipynb was getting too long.

README.md

@@ -11,7 +11,7 @@ in Antarctica using remote sensing and machine learning.
 
 ![ICESat-2 ATL11 rate of height change over time in Antarctica 2018-10-14 to 2020-05-13](https://user-images.githubusercontent.com/23487320/90118294-2601ff80-ddac-11ea-8b93-7bc9b15f2be0.png)
 
-![DeepIceDrain Pipeline](https://yuml.me/diagram/scruffy;dir:LR/class/[Land-Ice-Elevation|atl06_play.ipynb]->[Convert|atl06_to_atl11.ipynb],[Convert]->[Ice-Sheet-H(t)-Series|atl11_play.ipynb],[Ice-Sheet-H(t)-Series]->[Height-Change-over-Time-(dhdt)|atlxi_dhdt.ipynb])
+![DeepIceDrain Pipeline](https://yuml.me/diagram/scruffy;dir:LR/class/[Land-Ice-Elevation|atl06_play.ipynb]->[Convert|atl06_to_atl11.ipynb],[Convert]->[Ice-Sheet-H(t)-Series|atl11_play.ipynb],[Ice-Sheet-H(t)-Series]->[Height-Change-over-Time-(dhdt)|atlxi_dhdt.ipynb],[Height-Change-over-Time-(dhdt)]->[Subglacial-Lake-Finder|atlxi_lake.ipynb])
 
 # Getting started