geojson

go-whosonfirst-spr-geojson

Go package for translating Who's On First Standard Places Results (SPR) to GeoJSON.

Important

Work in progress. Documentation to follow.

Example

Using with spr.StandardPlacesResults

import (
	"context"
	"github.com/whosonfirst/go-reader"
	"github.com/whosonfirst/go-whosonfirst-spr-geojson"
	"os"
)

func main() {

	ctx := context.Background()

	results, _ := SomethingThatReturnsAStandardPlacesResults()

	reader_uri := "fs://usr/local/data/whosonfirst-data-admin-us"
	r, _ := reader.NewReader(ctx, reader_uri)
	
	opts := &geojson.AsFeatureCollectionOptions{
		Reader: r:
		Writer: os.Stdout,
	}

	geojson.AsFeatureCollection(ctx, results, opts)
}

Using with JSON-encoded spr.StandardPlacesResults

import (
	"bufio"
	"context"
	"github.com/whosonfirst/go-reader"
	"github.com/whosonfirst/go-whosonfirst-spr-geojson"
	"io/ioutil"
	"os"
)

func main() {

	reader_uri := "fs://usr/local/data/whosonfirst-data-admin-us"
	path := "places.#.wof:path"

	ctx := context.Background()

	r, _ := reader.NewReader(ctx, reader_uri)

	resolver_func := geojson.JSONPathResolverFunc(path)

	as_opts := &geojson.AsFeatureCollectionOptions{
		Reader: r:
		Writer: os.Stdout,
		JSONPathResolver: resolver_func,		
	}

	reader := bufio.NewReader(os.Stdin)
	body, _ := ioutil.ReadAll(reader)

	geojson.AsFeatureCollectionWithJSON(ctx, body, path, as_opts)
}

Here's how you might use this with "plain old" GeoJSON records that use a WOF-style ID/URI structure:

import (
	"bufio"
	"context"
	"github.com/whosonfirst/go-reader"
	"github.com/whosonfirst/go-whosonfirst-spr-geojson"
	"io/ioutil"
	"os"
)

func main() {

	reader_uri := "fs://usr/local/data/woeplanet-state-us/data"
	path := "places.#.spr:id"

	ctx := context.Background()

	r, _ := reader.NewReader(ctx, reader_uri)

	cb = func(ctx context.Context, path string) (string, error) {
		return geojson.WhosOnFirstPathWithString(path)
	}

	resolver_func := geojson.JSONPathResolverFuncWithCallback(path, cb)
	
	as_opts := &geojson.AsFeatureCollectionOptions{
		Reader: r:
		Writer: os.Stdout,
		JSONPathResolver: resolver_func,		
	}

	reader := bufio.NewReader(os.Stdin)
	body, _ := ioutil.ReadAll(reader)

	geojson.AsFeatureCollectionWithJSON(ctx, body, as_opts)
}

Here's what's going on:

• We're using data from the woeplanet-state-us repository. In this case we have a local checkout (as defined by the reader_uri variable).
• We're assuming that woeplanet-data SPR records are being passed in with a JSON encoding mapping the spr.Id() method to a spr:id property.
• W're also taking it for granted that woeplanet-data records have numeric IDs and are stored using the same nested directory structure as Who's On First records.
• The geojson.JSONPathResolverFunc returns a list of WOEPlanet IDs (using the places.#.spr:id syntax defined in the path variable).
• Each WOEPlanet Id is transformed in to a Who's On First style path using the callback defined by the cb variable.
• Theses are the final paths that are passed to the reader.Reader instance for loading the actual GeoJSON record.

Tools

To build binary versions of these tools run the cli Makefile target. For example:

$> make cli
go build -mod vendor -o bin/as-geojson cmd/as-geojson/main.go

as-geojson

$> ./bin/as-geojson -h
Usage of ./bin/as-geojson:
  -path string
    	A valid tidwall/gjson query path for finding the path for each element in your SPR response. (default "places.#.wof:path")
  -reader-uri string
    	A valid whosonfirst/go-reader URI.

The as-geojson tool reads a JSON-encoded Standard Places Results (SPR) document on STDIN and outputs a GeoJSON FeatureCollection document on STDOUT.

Internally it uses a whosonfirst/go-reader Reader instance to resolve SPR paths to Who's On First records.

For example, here's how you might use the as-geojson tool in concert with a tool like go-whosonfirst-spatial-sqlite's query which outputs SPR results as JSON and the jq tool for querying the final GeoJSON FeatureCollection.

In this example the query tool is using a SQLite database to generate SPR results. The as-geojson tool is using a local filesystem reader to resolve SPR paths in to Who's On First records.

$> /usr/local/go-whosonfirst-spatial-sqlite/bin/query \
	-database-uri 'sqlite://?dsn=/usr/local/data/ca-alt.db' \
	-latitude 45.572744 \
	-longitude -73.586295 \

| ./bin/as-geojson \
	-reader-uri fs:///usr/local/data/whosonfirst-data-admin-ca/data \

| jq '.features[]["properties"]["wof:id"]'

85874359
1108955735
85874359
136251273
85633041
136251273
85633041
136251273
85633041
890458661
85633041

Readers

This package uses the go-reader.Reader interface for retrieving data associated with a Who's On First record. The only reader that is available by default, with this package, is the local filesystem reader (fs://). If you need to use other go-reader.Reader implementations in your code you will need to import them explicitly.

See also

• https://github.com/whosonfirst/go-whosonfirst-spr
• https://github.com/whosonfirst/go-reader