UNL CORE JS
This library can be used to convert a UNL locationId to/from a latitude/longitude point. It also contains helper functions like retrieving the bounds of a UNL cell or the UNL grid lines for a given boundingbox (these can be used to draw a UNL cell or a UNL grid).
Install
npm install unl-coreyarn add unl-coreTypeScript
npm install @types/unl-core --save-devyarn add @types/unl-core --devUsage
You can either import certain functions from the package directly:
import { encode } from "unl-core";or load the whole library:
import UnlCore from "unl-core";Usage in browser
UnlCore can be used in the browser by taking a local copy, or loading it from jsDelivr: for example,
<!DOCTYPE html><title>locationId example</title><meta charset="utf-8" />
<script type="module">
import UnlCore from "https://cdn.jsdelivr.net/npm/unl-core@2.0.2";
const locationId = UnlCore.encode(52.2, 0.12, 6);
console.assert(locationId == "u120fw");
const latlon = UnlCore.decode("u120fw");
console.assert(JSON.stringify(latlon) == '{"lat":52.1988,"lon":0.115}');
</script>Usage in Node.js
UnlCore can be used in a Node.js app from npm (currently the esm package is required to load ES-modules):
$ npm install unl-core esm
$ node -r esm
> import UnlCore from 'unl-core';
> const locationId = UnlCore.encode(52.20, 0.12, 6);
> console.assert(locationId == 'u120fw');
> const latlon = UnlCore.decode('u120fw');
> console.assert(JSON.stringify(latlon) == '{"lat":52.1988,"lon":0.115}');Interfaces
Direction
type Direction = "N" | "S" | "E" | "W";
ElevationType
type ElevationType = "floor" | "heightincm";
Neighbours
interface Neighbours {
n: string;
ne: string;
e: string;
se: string;
s: string;
sw: string;
w: string;
nw: string;
}
Point
interface Point {
lat: number;
lon: number;
}
Bounds
interface Bounds {
sw: Point;
ne: Point;
}
PointWithElevation
interface PointWithElevation extends Point {
elevation: number;
elevationType: ElevationType;
bounds: Bounds;
}
EncodeOptions
interface EncodeOptions {
elevation: number;
elevationType: ElevationType;
}
LocationIdWithElevation
interface LocationIdWithElevation {
elevation: number;
elevationType: ElevationType;
locationId: string;
}Functions
encode(lat: number, lon: number, precision?: number, options?: EncodeOptions): string
Encodes latitude/longitude coordinates to locationId, either to specified precision or to default precision. Elevation information can be optionally specified in options parameter.
UnlCore.encode(52.37686, 4.90065);Returns a string:
"u173zwbt3"
decode(locationId: string): PointWithElevation
Decodes a locationId to latitude/longitude (location is approximate centre of locationId cell, to reasonable precision).
UnlCore.decode("u173zwbt3");Returns a Point object:
{
lat: centerLat,
lon: centerLon,
bounds: {
n: maxLat,
e: maxLon,
s: minLat,
w: minLon
}
}
bounds(locationId: string): Bounds
Returns SW/NE latitude/longitude bounds of specified locationId cell.
UnlCore.bounds("u173zwbt3");Returns a Bounds object:
{
n: maxLat,
e: maxLon,
s: minLat,
w: minLon
}
function gridLines(bounds: Bounds, precision?: number): Array<[[number, number], [number, number]]>
Returns the vertical and horizontal lines that can be used to draw a UNL grid in the specified SW/NE latitude/longitude bounds and precision. Each line is represented by an array of two coordinates in the format: [[startLon, startLat], [endLon, endLat]].
UnlCore.gridLines({
n: 52.38788170348322,
e: 4.91476651006799,
s: 52.369915397800824,
w: 4.88533463041897
});Returns an array of lines:
[
[[startLon, startLat], [endLon, endLat]]
...
]
adjacent(locationId: string, direction: Direction): string
Determines adjacent cell in given direction.
UnlCore.adjacent("ezzz@5", "N");Returns a string:
"gbpb@5"
neighbours(locationId: string): Neighbours
Returns all 8 adjacent cells to specified locationId.
UnlCore.neighbours("ezzz");Returns a Neighbours object :
{
n: "gbpb",
ne: "u000",
e: "spbp",
se: "spbn",
s: "ezzy",
sw: "ezzw",
w: "ezzx",
nw: "gbp8",
}
excludeElevation(locationIdWithElevation: string): LocationIdWithElevation
Returns locationId and elevation properties. It is mainly used by internal functions.
UnlCore.excludeElevation("6gkzwgjz@5");Returns a LocationIdWithElevation object:
{
locationId: "6gkzwgjz",
elevation: 5,
elevationType: "floor",
}
appendElevation(locationIdWithoutElevation: string, elevation: number, elevationType: ElevationType): string
Adds elevation chars and elevation. It is mainly used by internal functions.
UnlCore.appendElevation("6gkzwgjz", 5);Returns a string:
"6gkzwgjz@5"
Note
To obtain neighbours as an array, you can use
const neighboursObj = UnlCore.neighbours(locationId);
const neighboursArr = Object.keys(neighboursObj).map(n => neighboursObj[n]);
The parent of a locationId is simply locationId.slice(0, -1).
If you want the locationId converted from Base32 to Base4, you can e.g.:
parseInt(UnlCore.encode(52.20, 0.12, 6), 32).toString(4);
Upgrade to version 2.0 from version 1.0
In version 2.0 we renamed the concept of geohash to locationId. In order to upgrade from version 1.0 you need to:
- Import
UnlCoreinstead ofGeohashfromunl-core - Get
locationIdinstead ofgeohashfrom the answer of methods which returned an object withgeohashparameter