Standard Units

Different units and precisions can be used throughout the framework through the use of the unit API.

Built-in Units

• Acceleration units: Acceleration units used in IMU processing nodes.
• Angle units: Angle units needed for orientations or relative angle positions.
• Angular velocity units: Angular velocity unit to indicate the angular momentum.
• Linear velocity units: Linear velocity unit to indicate the linear momentum.
• Magnetism units: Magnetism unit for IMU sensors.
• Time units: Time units used to determine when sensor data was created or updated.
• Length units: Main unit inside a position. Used to describe a position or distance.

Creating a new basic unit

Creating a basic unit takes a baseName and one or more definitions. The base name indicates the type of unit (e.g. length, time, angle or in this case temperature).

ts
import { Unit } from '@openhps/core';
 
const CELCIUS = new Unit("celcius", {
    baseName: "temperature"
});
 
const FAHRENHEIT = new Unit("fahrenheit", {
    baseName: "temperature",
    definitions: [
        { unit: 'celcius', offset: -32, magnitude: 5 / 9 },
    ]
});
 
const KELVIN = new Unit("kelvin", {
    baseName: "temperature",
    definitions: [
        { unit: 'celcius', offset: -273.15 },
    ]
});
 
const RANKINE = new Unit("rankine", {
    baseName: "temperature",
    definitions: [
        { unit: 'kelvin', magnitude: 1 / 1.8 },
    ]
});

Creating a new derived unit

Derived units are units that are comprised of multiple other units. Similar to basic units, the unit has a base name, alias and optional definitions.

ts
import { LengthUnit, DerivedUnit, TimeUnit } from '@openhps/core';
 
const METER_PER_SECOND = new DerivedUnit('meter per second', {
    baseName: 'linearvelocity',
    aliases: ['m/s', 'meters per second'],
})
    .addUnit(LengthUnit.METER, 1)
    .addUnit(TimeUnit.SECOND, -1);
 
const CENTIMETER_PER_SECOND = METER_PER_SECOND.swap([LengthUnit.CENTIMETER], {
    baseName: 'linearvelocity',
    name: 'centimeter per minute',
    aliases: ['cm/min', 'centimeters per minute'],
});