You'll need a recent version of a good browser (tested in Chrome, FF, and Safari). You will need an install of Node 6.x because I use some ES6 features. To set up and run the project, execute the following commands in the project directory:
npm install
npm run startIf the app starts correctly, you should be able to view it here.
The app behaves similarly to Google Maps or other web map tools. Drag to pan, mousewheel to zoom in and out. If you hold shift and drag a rectangle, you will get an average temperature readout of the contained geography at the top of the screen.
Running the above will start a nodejs app that serves a bit of HTML and two API endpoints:
The first is a tile server that serves slippy map tiles in a MVT (Mapbox Vector Tile) format. MVT uses protobuf as a transport protocol, so very large numbers of points can be efficiently served; it can serve the half-million or so points in a few seconds across the wire at a cost of about 4.5 meg. To serve that in any other format, like geojson or topojson would involve hundreds of megs of data, huge amounts of RAM, or very high levels of simplification. (I tried several alternatives before resting on the current solution!) The tiles and basemap are rendered using MapboxGL.
The second endpoint fetches the average temperature for a given set of lat/lng bounds. This calls
the averageTemperature function and returns it to the UI. It can reduce over the entire nation
of data points in less than a second, which seems like satisfactory performance.