signalk-barograph
Version:
SignalK plugin to influx environment data & Barograph to visualize atmospheric pressure
326 lines (315 loc) • 11.6 kB
JavaScript
/*
conversions-module - specifically for SignalK Barograph, Dashboard & Logbook Apps
also required by OpenWeather Map | Squid Sailing Forecasting modules
*/
const crypto = require('crypto');
// Hash function for caching
function hashString(str) {
return crypto.createHash('md5').update(str).digest('hex');
}
// Beaufort Wind Scale
const BEAUFORT_SCALE = [
{ bft: 0, min: 0.0, max: 0.3 },
{ bft: 1, min: 0.3, max: 1.6 },
{ bft: 2, min: 1.6, max: 3.4 },
{ bft: 3, min: 3.4, max: 5.5 },
{ bft: 4, min: 5.5, max: 8.0 },
{ bft: 5, min: 8.0, max: 10.8 },
{ bft: 6, min: 10.8, max: 13.9 },
{ bft: 7, min: 13.9, max: 17.2 },
{ bft: 8, min: 17.2, max: 20.8 },
{ bft: 9, min: 20.8, max: 24.5 },
{ bft: 10, min: 24.5, max: 28.5 },
{ bft: 11, min: 28.5, max: 32.7 },
{ bft: 12, min: 32.7, max: 99.9 },
];
// return windspeed in m/s
function fromBeaufort(value, calc) {
if (typeof value==='string')
value = Number(value)
if (calc===undefined || (calc!=='min' && calc!=='max')) {
return 0.8360 * Math.pow(value, 3/2)
} else if (value>=0 && value <=12) {
return calc=='min' ? BEAUFORT_SCALE[value].min : calc=='max' ? BEAUFORT_SCALE[value].max : null;
} else
return null;
}
function toBeaufort (value) {
return Math.round(Math.pow(value / 0.8360), 2/3)
}
// returns Pressure at Station based on Pressure at SeaLevel, Elevation (m) and Temperature (K) at Station
// return pressure * Math.exp(-elevation / (temperature*29.263));
// see also: https://keisan.casio.com/exec/system/1224579725
function toStationAltitude (pressure, elevation, temperature) {
return pressure * Math.pow(1-(0.0065*elevation/(temperature+0.0065*elevation)), 5.257)
}
// returns Pressure at SeaLevel based on Pressure at Station, Elevation (m) and Temperature (K) at Station
// return pressure / Math.exp(-elevation / (temperature*29.263));
// see also: https://keisan.casio.com/exec/system/1224575267
function toSeaLevel (pressure, elevation, temperature) {
return pressure * Math.pow(1-(0.0065*elevation/(temperature+0.0065*elevation)), -1.0*5.257)
}
// converts to SignalK-Units
function toSignalK(unit, value) {
let skUnit
switch (unit)
{
case '%':
value = value / 100
skUnit = 'ratio'
break;
case '°C':
case 'deg':
value = value + 273.15
skUnit = 'K'
break;
case '°F':
value = (value - 32) * (5/9) + 273.15
skUnit = 'K'
break;
case 'kmh':
value = value / 3.6
skUnit = "m/s"
break;
case 'm s-1':
value = value * 1.0
skUnit = "m/s"
break;
case 'kn':
value = value / 1.943844
skUnit = "m/s"
break;
case unit.includes('Bft'):
value = fromBeaufort(value, (unit==='BftMin' ? 'min' : unit==='BftMax' ? 'max' : ''))
skUnit = "m/s"
break;
case '°':
case 'degrees':
value = value * (Math.PI/180.0)
skUnit = 'rad'
break;
case 'Pa':
value = value * 1.0
skUnit = "Pa"
break;
case 'hPa':
case 'mbar':
value = value * 100
skUnit = "Pa"
break;
case 'km':
value = value * 1000
skUnit = "m"
break;
case 'nm':
value = value * 1852
skUnit = "m"
break;
case 'm':
value = value * 1.0
skUnit = "m"
break;
case 'mm':
value = value * 1.0
skUnit = "mm"
break;
case 'J kg-1':
value = value * 1.0
skUnit = "J/kg"
break;
case 'kg m-2 s-1':
value = value * 1.0
skUnit = "mm/s"
break;
case 'string':
value = value
skUnit = ""
break;
case 'unixdate':
value = new Date(value * 1000).toISOString()
skUnit = ""
break;
case 'geoJson':
value = { latitude: value[1], longitude: value[0] }
skUnit = ""
break;
case 'latLng':
value = { latitude: value[0], longitude: value[1] }
skUnit = ""
break;
default:
value = value * 1.0
skUnit = unit
break;
}
return { value: value, units: skUnit }
}
let cachedFunctions = {}
// converts to Target as specified
function toTarget(skunit, value, target, precision) {
let unit
if ( target==='geoJson' || target==='latLng' ) {
let geo = []
if (value.longitude && value.latitude && target==='geoJson') {
geo.push(typeof precision==='number' ? value.longitude.toFixed(precision) : value.longitude)
geo.push(typeof precision==='number' ? value.latitude.toFixed(precision) : value.latitude)
if (value.altitude) geo.push(value.altitude)
value = geo
} else if (value.longitude && value.latitude && target==='latLng') {
geo.push(typeof precision==='number' ? value.latitude.toFixed(precision) : value.latitude)
geo.push(typeof precision==='number' ? value.longitude.toFixed(precision) : value.longitude)
if (value.altitude) geo.push(value.altitude)
value = geo
}
else
value = null
unit = target
} else {
switch (skunit)
{
case 'ratio':
if (!target || target==='%') {
value = value * 100.0
unit = target===undefined ? '' : '%'
} else if (target==='decimal' || target==='number') {
value = value * 1.0
unit = ''
}
break;
case 'K':
if (!target) {
value = value
unit = 'K'
} else if (target==="°C" || target==="deg") {
value = value - 273.15
unit = target
} else if (target==='°F') {
value = (value - 273.15) * (9/5) + 32
unit = target
}
break;
case 'm/s':
if (!target) {
unit = "m/s"
} else if (target==='kn') {
value = value * 1.943844
unit = target
} else if (target==='kmh') {
value = value * 3.6
unit = target
} else if (target==='mh') {
value = value * 2.23693629
unit = target
} else if (target==='Bft') {
value = toBeaufort(value)
unit = target
}
break;
case 'rad':
if (!target || target==='°' || target==='deg' || target==='') {
value = value * (180.0/Math.PI)
unit = '°'
}
break;
case 'Pa':
if (!target) {
unit = 'Pa'
} else if (target==='hPa' || target==='mbar') {
value = value / 100
unit = target
} else if (target ==='atm') {
value = value / 101325
unit = target
}
break;
case 'm':
if (!target || target === 'm') {
value = value * 1.0
unit = 'm'
} else if (target === 'km') {
value = value / 1000
unit = 'km'
} else if (target === 'nm') {
value = value / 1852
unit ='nm'
}
break;
case 'dt':
if (target === 'influx' || target === 'time' ) { // influx standard
value = (new Date(value).getTime())*1000*1000
unit ='ns'
} else if (target === 'ms' || target === 'unixdate' ) {
value = (new Date(value).getTime())
unit ='ms'
} else if (target === 's' ) {
value = (new Date(value).getTime())/1000
unit ='s'
}
break;
case 's':
if (target === 'ms' ) {
value = value * 1000
unit ='ms'
}
else if (target === 's' || target === 'sec' )
unit = target
else if (target === 'm' || target === 'min' ) {
value = value / 60
unit = target
} else if (target === 'h' || target === 'hour' ) {
value = value / 3600
unit = target
} else if (target === 'd' || target === 'day' ) {
value = value / 3600 / 24
unit = target
}
break;
case '{obj}':
if (target && value.hasOwnProperty(target) ) {
unit = value[target].hasOwnProperty('unit') ? value[target].unit : ''
value = value[target].hasOwnProperty('value') ? value[target].value : value[target]
}
break;
case '{fct}':
const hash = hashString(target)
let res = null
if (cachedFunctions.hasOwnProperty(hash))
res = cachedFunctions[hash](value)
else {
const fct = new Function('o', `return ${target}`)
res = fct(value)
cachedFunctions[hash] = fct
}
value = res ? res : null
unit = ''
break;
default:
unit = skunit
break;
}
}
if (typeof value==='number' && target!=='geoJson' && target!=='latLng' && typeof precision==='number')
value = parseFloat(value.toFixed(precision))
return { value: value, units: unit }
}
function toDegreesMinutesAndSeconds(coordinate) {
var absolute = Math.abs(coordinate);
var degrees = Math.floor(absolute);
var minutesNotTruncated = (absolute - degrees) * 60;
var minutes = Math.floor(minutesNotTruncated);
var seconds = Math.floor((minutesNotTruncated - minutes) * 60);
return degrees + "\°" + minutes + "\'" + seconds +"\"";
}
function toDMS (lat, lng) {
return `${toDegreesMinutesAndSeconds(lat)}${lat >= 0 ? "N" : "S"} : ${toDegreesMinutesAndSeconds(lng)}${lng >= 0 ? "E" : "W"}`;
}
module.exports = {
toBeaufort,
fromBeaufort,
toSeaLevel,
toStationAltitude,
toDegreesMinutesAndSeconds,
toDMS,
toSignalK,
toTarget
}