geojson-precision-ts
v1.3.1
Published
Remove meaningless precision from GeoJSON.
Downloads
290
Maintainers
Readme
geojson-precision-ts
Remove meaningless precision from your GeoJSON. If your coordinates go out to 7+ digits, you are probably misrepresenting your data. Most scenarios in which GeoJSON is useful (i.e. web-related applications) do not require survey-grade precision, and a higher value is placed on a compact file size. Trimming the precision of coordinates can greatly reduce file size, while removing the appearance of fake high precision.
This fork is rewritten in typescript.
Installation
npm install geojson-precision-ts
or
yarn add geojson-precision-ts
Usage
parse(*geojson*, *precision*, *extrasPrecision*, *options*);
omit(*geojson*);
| Parameter | Type | Default | Description |
| --------------- | ---------------- | --------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| geojson | GeoJSON | undefined | geojson
is a valid GeoJSON object, and can be of type Point
, LineString
, Polygon
, MultiPoint
, MultiPolygon
, MultiLineString
, GeometryCollection
, Feature
, or FeatureCollection
. If you are unsure whether or not your GeoJSON object is valid, you can run it through a linter such as geojsonhint. |
| precision | number | 6 | precision
is a positive integer. If your specified precision
value is greater than the precision of the input geometry, the output precision will be the same as the input. For example, if your input coordinates are [10.0, 20.0]
, and you specify a precision
of 5
, the output will be the same as the input. |
| extrasPrecision | number | 2 | extrasPrecision
is a positive integer. If your specified extrasPrecision
value is greater than the precision of the input geometry, the output precision will be the same as the input. For example, if your input coordinates are [10.0, 20.0]
, and you specify a precision
of 5
, the output will be the same as the input. |
| options | OptionsInterface |
options
are bellows:
| Option | Type | Default | Description | | ---------------- | ------- | ------- | -------------------------------------- | | ignorePoint | boolean | false | Skip Point | | ignoreLineString | boolean | false | Skip LineString | | ignorePolygon | boolean | false | Skip Polygon | | removeDuplicates | boolean | false | Delete points at the same coordinates. |
omit()
is an alias for parse(t, 0, 0, { removeDuplicates: true })
, a function that removes all decimal coordinates from GeoJSON.
How do you choose tolerance?
Tolerance corresponds to how much resolution you can spare. Higher the tolerance, lower is your geometry's resolution. Tolerance is specified in degrees. The above table applies here too. The table gives a general idea on what tolerance to use for your task. For example, if you can allow an error of 1.11km (for example while plotting a big city map) set your tolerance to 0.01.
decimal
places degrees distance
------- ------- --------
0 1 111 km
1 0.1 11.1 km
2 0.01 1.11 km
3 0.001 111 m
4 0.0001 11.1 m
5 0.00001 1.11 m
6 0.000001 11.1 cm
7 0.0000001 1.11 cm
8 0.00000001 1.11 mm
Example
parse()
function
import { parse } from 'geojson-precision-ts';
const trimmed = parse(
{
type: 'Point',
coordinates: [18.984375, 57.32652122521709],
},
3
);
trimmed
will now look like this:
{
"type": "Point",
"coordinates": [18.984, 57.326]
}
omit()
function
This is useful when you want to pin a static image by specifying pixels.
import { parse } from 'geojson-precision-ts';
const omitted = omit({
type: 'Point',
coordinates: [18.984375, 57.32652122521709],
});
omiited
will now look like this:
{
"type": "Point",
"coordinates": [18, 57]
}
CLI
Geojson-precision can also be used via the command line when installed globally (using -g
).
Parameters
precision (-p)
A positive integer specifying coordinate precision
extras precision (-e)
A positive integer specifying extra coordinate precision for things like the z value when the coordinate is [longitude, latitude, elevation].
input
An input GeoJSON file
output
An output GeoJSON file
Example use
geojson-precision -p 4 input.json output.json
Inspiration
Concepts, ideas, etc borrowed to various degrees from:
License
MIT
Original Version by jczaplew's geojson-precision.
TypeScript version by Logue.
- Stop mutation of original object feature by frankrowe.
- Skip each geometry type feature by andrewharvey.
- Remove duplicate points feature by matthewrj.