Static file generation backend

The code in this directory is responsible for generating the data (.fp16.br) files and inventory (inventory.json.br) file under the public/tera directory, which is symlinked to dist/tera during the build step. Each data source (e.g. GFS, GEOS) has a single .js file with a forage function that recieves the source's current state, creating new data files based on that state, then returning the new state.

File formats

Data files (.fp16.br)

These are raw binary files containing only fp16 values compressed with Brotli. All metadata is contained in public/data/inventory.json.br.

Inventory file (inventory.json.br)

The inventory file is a JSON array of datasets. There are two types of datasets, differentiated by their keys.

Shared by both datasets

key	value type	meaning	example
name	string	a short phrase fully describing the data	"temperature at 2 m above ground"
path	path string	absolute path of data directory	"/data/gfs-0p25-temperature-2-m-above-ground/"
width	integer	horizontal/longitude dimension of data	1440
height	integer	vertical/latitude dimension of data	721
interval	string	time between each data file (see /src/intervals.js)	hourly
projection	dataProjection string (see /src/map/data-projections/index.js)	conversion between row/col and lat/lon	"GFS"
start	ISO date string	filename, excluding .fp16.br extension, of earliest data	"2021-07-03T12:00:00.000Z"
end	ISO date string	filename, excluding .fp16.br extension, of most future data	"2021-07-03T21:00:00.000Z"

Gridded datasets only

key	value type	meaning	example
unit	unit string (from js-quantities library)	default display unit of measurement	"tempC"
originalUnit	unit string (from js-quantities library)	in the .fp16.br files, unit of measurement data is in	"tempK"
domain	length-2 array of floats	minimum and max values, in term of originalUnit, to display	[193.14999999999998, 328.15]
colormap	colormap string (see /src/map/colormaps/index.js)	how to convert values to colors for display	"VIRIDIS"

Particle datasets only

key	value type	meaning	example
particleLifetime	float	how long, in milliseconds, before a particle is relocated on map	2000
particleCount	integer	total number of particles simulated at any time	1e5
particleDisplay	object (see rows below)	various ways to affect particle (trail) rendering	{...} (see rows below)
particleDisplay.size	float	at 1 zoom, diameter of the particle in CSS pixels	0.8
particleDisplay.rate	float	how many times faster than reality the particles move across the globe	25000
particleDisplay.opacity	float	from 0 to 1, a base for opaque the particles are	0.3
particleDisplay.opacitySpeedDecay	float	scale for how transparent slower-moving particles are	0.8
particleDisplay.fade	float	from 0 to 1, how slow the particle trail goes to 0 opacity	0.98