points2polygons

Given a list of polygons and points, points2polygons will determine if each point is inside a polygon, using point-in-polygon.

If found, the point will be added to the polygon.

For example:

Given a list of polygons, polygons.geojson:

{
    "type": "FeatureCollection",
    "features": [
        {
            "type": "Feature",
            "properties": { },
            "geometry": {
                "type": "Polygon",
                "coordinates": [
                    [
                        [0,0],
                        ...

and a list of points, points.csv:

address,        lat, lon
111 Point Lane, 1,   1

points2polygons will assign points to matching polygons, and generate a new GeoJSON file:

{
    "type": "FeatureCollection",
    "features": [
        {
            "type": "Feature",
            "properties": {
                "points": [
                    {
                        "type": "Feature",
                        "properties": {
                            "address": "111 Point Lane"
                        }
                        "geometry": {
                            "type": "Point",
                            "coordinates": [1,1]
                        }
                    }
                ]
            },
            "geometry": {
                "type": "Polygon",
                "coordinates": [
                    [
                        [0,0],
                        ...

Points with no polygons will be placed in their own GeoJSON file, orphans.geojson.

Aggregation!

points2polygons can perform sum and count aggregations. Let me explain. Say you have a town.geojson:

{
    "type": "Feature",
    "properties": {
        "name": "Polygonville"
    },
    "geometry": {
        "type": "Polygon",
        "coordinates": [
            [
                [0,0],

and houses.csv:

address,        color, value, latitude, longitude
111 Point Lane, red,   100,   1,        1
222 Point Lane, green, 200,   2,        2
333 Point Lane, red,   300,   3,        3

Running points2polygons --polygons town.geojson --points houses.csv will correctly place the houses in our town, and generate something like this:

{
    "type": "FeatureCollection",
    "features": [
        {
            "type": "Feature",
            "properties": {
                "name": "Polygonville",
                "points": [
                    // a house
                    {
                        "type": "Feature",
                        "properties": {
                            "address": "111 Point Lane",
                            "color": "red",
                            "value": "100"
                        }
                        "geometry": {
                            "type": "Point",
                            "coordinates": [1,1]
                        }
                    },
                    // another house
                    {
                        "type": "Feature",
                        "properties": {
                            "address": "222 Point Lane",
                            "color": "green",
                            "value": "200"
                        }
                        "geometry": {
                            "type": "Point",
                            "coordinates": [2,2]
                        }
                    },
                    ...
                ]
            },
            "geometry": {
                "type": "Polygon",
                "coordinates": [
                    [
                        [0,0],

But what I really want is a count of red and green houses in my town. In other words, I want to

count

by color. Use the --count param. Running points2polygons --polygons town.geojson --points houses.csv --count color generates something like this:

{
    "type": "FeatureCollection",
    "features": [
        {
            "type": "Feature",
            "properties": {
                "name": "Polygonville",
                "green": 1, // there is one green house in the town
                "red": 2 // there are two red houses in the town
            },
            "geometry": {
                "type": "Polygon",
                "coordinates": [
                    [
                        [0,0],

properties doesn't contain points anymore, only the aggregation result.

Pretty incredible! But what I really want is a total of house values, by color. In other words, I want to

sum

value, and group by color. Use the --groupBy and --sum params. Running points2polygons --polygons town.geojson --points houses.csv --groupBy color --sum value generates something like this:

{
    "type": "FeatureCollection",
    "features": [
        {
            "type": "Feature",
            "properties": {
                "name": "Polygonville",
                "green": 200, // this town's green houses are worth a total of 200
                "red": 400 // this towns's red houses are worth a total of 400
            },
            "geometry": {
                "type": "Polygon",
                "coordinates": [
                    [
                        [0,0],

Pretty incredible!

Installation

npm install points2polygons

Using it as a console utility

➜ points2polygons
Batch point-in-polygon operations. Creates a GeoJSON file of polygons containing points.
Usage: points2polygons

Options:
  -y, --polygons   a GeoJSON file of polygons                        [required]
  -t, --points     a CSV file of points                              [required]
  -i, --latitude   latitude field                                    [default: "latitude"]
  -e, --longitude  longitude field                                   [default: "longitude"]
  -d, --delimiter  delimiter character                               [default: ","]
  -o, --output     a GeoJSON file of polygons containing points      [default: "output.json"]
  -c, --count      aggregate points and count - group by this field  [default: null]
  -g, --groupBy    aggregate points and sum - group by this field    [default: null]
  -s, --sum        aggregate points and sum - sum this field         [default: null]

Using it as a library

require('points2polygons')

.batch(polygons, points, showProgress, count, groupBy, sum)

• polygons: (required) a GeoJSON object of polygons.
• points: (required) a GeoJSON object of points.
• showProgress: (optional) a callback that gets fired per point processed, and receives the current point index.
• count: (optional) if provided, will aggregate points and count this field. See example.
• groupBy: (optional) if provided, will aggregate points and sum, grouping by this field. See example.
• sum: (optional) if provided, will aggregate points and sum, summing by this field. See example.

Returns an object with two properties:

• polygons: same as input, but each polygon has a points property containing corresponding points.
• orphans: a GeoJSON object containing points with no polygons.

See also

• point-in-polygon: determine if a point is inside a polygon.
• csv2geojson: magically convert csv files to geojson files.