Merge pull request pierremtb#12 from thomas-gruen/fix-mph

fixed speed conversion for 'mph' (miles per hour)
babgvant · Apr 6, 2020 · 1ef078f · 1ef078f
2 parents 15d2be0 + 357c1c5
commit 1ef078f
Showing 1 changed file with 31 additions and 4 deletions.
diff --git a/src/fit.js b/src/fit.js
@@ -1,31 +1,58 @@
+// some unit conversion constants
+const metersInOneKilometer = 1000;
+const secondsInOneHour = 3600;
+// according to https://en.wikipedia.org/wiki/Mile
+const metersInOneMile = 1609.344;
+
 export const FIT = {
   scConst: 180 / Math.pow(2, 31),
   options: {
     speedUnits: {
+      // native speed unit: meters per second [m/s]
+      'm/s': {
+        multiplier: 1,
+        offset: 0,
+      },
+      // miles per hour [mph]
       mph: {
-        multiplier: 3.6 / 1.4,
+        multiplier: secondsInOneHour / metersInOneMile,
         offset: 0,
       },
+      // kilometers per hour [km/h]
       'km/h': {
-        multiplier: 3.6,
+        multiplier: secondsInOneHour / metersInOneKilometer,
         offset: 0,
       },
     },
     lengthUnits: {
+      // native length unit: meters [m]
+      m: {
+        multiplier: 1,
+        offset: 0,
+      },
+      // (international) mile [mi]
       mi: {
-        multiplier: 1 / 1609.344,
+        multiplier: 1 / metersInOneMile,
         offset: 0,
       },
+      // kilometer [km]
       km: {
-        multiplier: 1 / 1000,
+        multiplier: 1 / metersInOneKilometer,
         offset: 0,
       },
     },
     temperatureUnits: {
+      // native temperature unit: degree Celsius [°C]
+      '°C': {
+        multiplier: 1,
+        offset: 0,
+      },
+      // kelvin [K]
       kelvin: {
         multiplier: 1,
         offset: -273.15,
       },
+      // degree fahrenheit [°F]
       fahrenheit: {
         multiplier: 9/5,
         offset: 32