geo

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 Go to latest Published: May 10, 2015 License: MIT Imports: 17 Imported by: 0

README 

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♫ around the world ♪

Build Status Coverage Status GoDoc

what

This library provides convenience functions for translating, geocoding, and calculating distances between geographical points. It is inspired by ruby's geokit and geokit-rails gems, and aims to make working with geographical data a little bit easier in golang.

documentation

You can read the documentation here.

usage

Import from github to get started!

package main

import("github.com/kellydunn/golang-geo"
       "fmt")

func main() {
     // Make a few points
     p := geo.NewPoint(42.25, 120.2)
     p2 := geo.NewPoint(30.25, 112.2)
     
     // find the great circle distance between them
     dist := p.GreatCircleDistance(p2)
     fmt.Printf("great circle distance: %d\n", dist)
}

Currently, golang-geo provides the following functionality:

  • Transposing a point for a given distance and bearing.
  • Calculating the Great Circle Distance bewteen two points.
  • Geocoding an address using Google Maps, Mapquest (OpenStreetMap data), OpenCage (OpenStreetMap, twofishes and other data sources) API.
  • Reverse Geocoding a Point using the same services.
  • Querying for points within a radius using your own SQL data tables.

Keep in mind that you do not need to use SQL in order to perform simple Point operations and the only function that relies on SQL is PointsWithinRadius.

using SQL

As of 0.1.0, golang-geo will shift its scope of responsiblity with SQL management. The library will still support the functions exposed in its public API in the past, however, it will not concern itself so much with creating and maintaining *sql.DB connections as it has done in previous versions. It is suggested that if you are using geo.HandleWithSql that you should instead consider creating a geo.SQLMapper yourself by calling the newly introduced geo.NewSQLMapper method, which accepts a *sql.DB connection and a filepath to the configuration file used to inform golang-geo of your particular SQL setup.

That being said, geo.HandleWithSQL is configured to connect to a SQL database by reading a config/geo.yml file in the root level of your project. If it does not exist, it will use a Default SQL configuration that will use the postgres driver as described by lib/pq. The Default SQL configuration will attempt to connect as a user named "postgres" and with the password "postgres" to a database named "points".

examples of SQL database configurations

Here are some examples of valid config files that golang-geo knows how to process:

PostgreSQL
development:
  driver: postgres
  openStr: user=username password=password dbname=points sslmode=disable
  table: points
  latCol: lat
  lngCol: lng
MySQL
development:
  driver: mysql
  openStr: points/username/password
  table: points
  latCol: lat
  lngCol: lng

notes

  • golang-geo currently only uses metric measurements to do calculations
  • The $GO_ENV environment variable is used to determine which configuration group in config.yml is to be used. For example, if you wanted to use the PostgreSQL configuration listed above, you could specify GO_ENV=development which would read config.yml and use the configuration under the root-level key development.

installing older versions of golang-geo

With the advent of gopkg.in, you can now install older versions of golang-geo! Consult CHANGELOG.md for the version you wish to build against.

roadmap

  • More Tests!
  • Redis / NOSQL Mapper
  • Bing Maps?
  • Add an abstraction layer for PostgreSQL earthdistance / PostGIS

testing

By default, golang-geo will attempt to run its test suite against a PostgreSQL database. However, you may run the tests with mocked SQL queries by specifying that you want to do so on the command line:

DB=mock GO_ENV=test go test

The $DB environment variable is used to specify which database you'd like to run the tests against. You may specify postgres, mysql, or mock. The Travis CI builds for this project currently runs against all of these when running the test suite.

contributing

  • Fork the project
  • Create a topic branch (preferably the in the gitflow style of feature/, hotfix/, etc)
  • Make your changes and write complimentary tests to ensure coverage.
  • Submit Pull Request (on develop) once the full test suite is passing.
  • Pull Requests will then be reviewed by the maintainer and the community and hopefully merged!

Thanks!

Documentation

Index

Constants

View Source 
const (
	DEFAULT_PGSQL_OPEN_STR = "user=postgres dbname=points sslmode=disable"
	DEFAULT_MYSQL_OPEN_STR = "points/root/"
	DEFAULT_TEST_OPEN_STR  = "\"\""
)
View Source 
const (
	// According to Wikipedia, the Earth's radius is about 6,371km
	EARTH_RADIUS = 6371
)

Variables

View Source 
var GoogleAPIKey = ""
View Source 
var MapquestAPIKey = ""
View Source 
var OpenCageAPIKey = ""

Functions

func SetGoogleAPIKey 

func SetGoogleAPIKey(newAPIKey string)

func SetGoogleGeocodeURL 

func SetGoogleGeocodeURL(newGeocodeURL string)

Note: In the next major revision (1.0.0), it is planned 

That Geocoders should adhere to the `geo.Geocoder`
interface and provide versioning of APIs accordingly.

Sets the base URL for the Google Geocoding API.

func SetMapquestAPIKey 

func SetMapquestAPIKey(newAPIKey string)

func SetMapquestGeocodeURL 

func SetMapquestGeocodeURL(newGeocodeURL string)

Note: In the next major revision (1.0.0), it is planned 

That Geocoders should adhere to the `geo.Geocoder`
interface and provide versioning of APIs accordingly.

Sets the base URL for the MapQuest Geocoding API.

func SetOpenCageAPIKey 

func SetOpenCageAPIKey(newAPIKey string)

func SetOpenCageGeocodeURL 

func SetOpenCageGeocodeURL(newGeocodeURL string)

Note: In the next major revision (1.0.0), it is planned 

That Geocoders should adhere to the `geo.Geocoder`
interface and provide versioning of APIs accordingly.

Sets the base URL for the OpenCage Geocoding API.

Types

type Geocoder 

type Geocoder interface {
	Geocode(query string) (*Point, error)
	ReverseGeocode(p *Point) (string, error)
}

This interface describes a Geocoder, which provides the ability to Geocode and Reverse Geocode geographic points of interest. Geocoding should accept a string that represents a street address, and returns a pointer to a Point that most closely identifies it. Reverse geocoding should accept a pointer to a Point, and return the street address that most closely represents it.

type GoogleGeocoder 

type GoogleGeocoder struct {
	HttpClient *http.Client
}

This struct contains all the funcitonality of interacting with the Google Maps Geocoding Service

func (*GoogleGeocoder) Geocode 

func (g *GoogleGeocoder) Geocode(address string) (*Point, error)

Geocodes the passed in query string and returns a pointer to a new Point struct. Returns an error if the underlying request cannot complete.

func (*GoogleGeocoder) Request 

func (g *GoogleGeocoder) Request(params string) ([]byte, error)

Issues a request to the google geocoding service and forwards the passed in params string as a URL-encoded entity. Returns an array of byes as a result, or an error if one occurs during the process. Note: Since this is an arbitrary request, you are responsible for passing in your API key if you want one.

func (*GoogleGeocoder) ReverseGeocode 

func (g *GoogleGeocoder) ReverseGeocode(p *Point) (string, error)

Reverse geocodes the pointer to a Point struct and returns the first address that matches or returns an error if the underlying request cannot complete.

type MapQuestGeocoder 

type MapQuestGeocoder struct{}

This struct contains all the funcitonality of interacting with the MapQuest Geocoding Service

func (*MapQuestGeocoder) Geocode 

func (g *MapQuestGeocoder) Geocode(address string) (*Point, error)

Returns the first point returned by MapQuest's geocoding service or an error if one occurs during the geocoding request.

func (*MapQuestGeocoder) Request 

func (g *MapQuestGeocoder) Request(url string) ([]byte, error)

Issues a request to the open mapquest api geocoding services using the passed in url query. Returns an array of bytes as the result of the api call or an error if one occurs during the process. Note: Since this is an arbitrary request, you are responsible for passing in your API key if you want one.

func (*MapQuestGeocoder) ReverseGeocode 

func (g *MapQuestGeocoder) ReverseGeocode(p *Point) (string, error)

Returns the first most available address that corresponds to the passed in point. It may also return an error if one occurs during execution.

type Mapper 

type Mapper interface {
	PointsWithinRadius(p *Point, radius int) bool
}

This interface describes a Mapper, which should be a data storage mechanism that can execute interesting queries. Currently, mappers should be able to find points within a radius of an origin point.

type OpenCageGeocoder 

type OpenCageGeocoder struct{}

This struct contains all the funcitonality of interacting with the OpenCage Geocoding Service

func (*OpenCageGeocoder) Geocode 

func (g *OpenCageGeocoder) Geocode(address string) (*Point, error)

Returns the first point returned by OpenCage's geocoding service or an error if one occurs during the geocoding request.

func (*OpenCageGeocoder) Request 

func (g *OpenCageGeocoder) Request(url string) ([]byte, error)

Issues a request to the open OpenCage API geocoding services using the passed in url query. Returns an array of bytes as the result of the api call or an error if one occurs during the process. Note: Since this is an arbitrary request, you are responsible for passing in your API key if you want one.

func (*OpenCageGeocoder) ReverseGeocode 

func (g *OpenCageGeocoder) ReverseGeocode(p *Point) (string, error)

Returns the first most available address that corresponds to the passed in point. It may also return an error if one occurs during execution.

type Point 

type Point struct {
	// contains filtered or unexported fields
}

Represents a Physical Point in geographic notation [lat, lng].

func NewPoint 

func NewPoint(lat float64, lng float64) *Point

Returns a new Point populated by the passed in latitude (lat) and longitude (lng) values.

func (*Point) BearingTo 

func (p *Point) BearingTo(p2 *Point) float64

Calculates the initial bearing (sometimes referred to as forward azimuth) Original Implementation from: http://www.movable-type.co.uk/scripts/latlong.html

func (*Point) GreatCircleDistance 

func (p *Point) GreatCircleDistance(p2 *Point) float64

Calculates the Haversine distance between two points in kilometers. Original Implementation from: http://www.movable-type.co.uk/scripts/latlong.html

func (*Point) Lat 

func (p *Point) Lat() float64

Returns Point p's latitude.

func (*Point) Lng 

func (p *Point) Lng() float64

Returns Point p's longitude.

func (*Point) MarshalJSON 

func (p *Point) MarshalJSON() ([]byte, error)

Renders the current Point to valid JSON. Implements the json.Marshaller Interface.

func (*Point) PointAtDistanceAndBearing 

func (p *Point) PointAtDistanceAndBearing(dist float64, bearing float64) *Point

Returns a Point populated with the lat and lng coordinates by transposing the origin point the passed in distance (in kilometers) by the passed in compass bearing (in degrees). Original Implementation from: http://www.movable-type.co.uk/scripts/latlong.html

func (*Point) UnmarshalJSON 

func (p *Point) UnmarshalJSON(data []byte) error

Decodes the current Point from a JSON body. Throws an error if the body of the point cannot be interpreted by the JSON body

type Polygon 

type Polygon struct {
	// contains filtered or unexported fields
}

A Polygon is carved out of a 2D plane by a set of (possibly disjoint) contours. It can thus contain holes, and can be self-intersecting.

func NewPolygon 

func NewPolygon(points []*Point) *Polygon

Creates and returns a new pointer to a Polygon composed of the passed in points. Points are considered to be in order such that the last point forms an edge with the first point.

func (*Polygon) Add 

func (p *Polygon) Add(point *Point)

Appends the passed in contour to the current Polygon.

func (*Polygon) Contains 

func (p *Polygon) Contains(point *Point) bool

Returns whether or not the current Polygon contains the passed in Point.

func (*Polygon) IsClosed 

func (p *Polygon) IsClosed() bool

Returns whether or not the polygon is closed. TODO: This can obviously be improved, but for now, 

this should be sufficient for detecting if points
are contained using the raycast algorithm.

func (*Polygon) Points 

func (p *Polygon) Points() []*Point

Returns the points of the current Polygon.

type SQLConf 

type SQLConf struct {
	// contains filtered or unexported fields
}

Provides a set of configuration variables that describe how to interact with a SQL database.

func GetSQLConf 

func GetSQLConf() (*SQLConf, error)

Attempts to read config/geo.yml, and creates a SQLConf as described therein. Returns the DefaultSQLConf if no config/geo.yml is found, or an error if one arises during the process of parsing the configuration file.

func GetSQLConfFromFile 

func GetSQLConfFromFile(filename string) (*SQLConf, error)

Attempts to read from the passed in filename and creates a SQLconf as described therin. Retruns the DefaultSQLConf if the file cannot be found, or an error if one arises during the process of parsing the configuration file.

type SQLMapper 

type SQLMapper struct {
	// contains filtered or unexported fields
}

A Mapper that uses Standard SQL Syntax to perform mapping functions and queries

func HandleWithSQL 

func HandleWithSQL() (*SQLMapper, error)

Retrieves the SQL configuration specified in config.yml that resides at the root level of the project. Returns a pointer to a SQLMapper if successful, or an error if there is an issue opening a database connection.

func NewSQLMapper 

func NewSQLMapper(filename string, conn *sql.DB) (*SQLMapper, error)

Creates and returns a pointer to a new geo.SQLMapper.

func (*SQLMapper) PointsWithinRadius 

func (s *SQLMapper) PointsWithinRadius(p *Point, radius float64) (*sql.Rows, error)

Uses SQL to retrieve all points within the radius (in meters) passed in from the origin point passed in. Original implemenation from : http://www.movable-type.co.uk/scripts/latlong-db.html Returns a pointer to a sql.Rows as a result, or an error if one occurs during the query.

func (*SQLMapper) SqlDbConn 

func (s *SQLMapper) SqlDbConn() *sql.DB

Returns a pointer to the SQLMapper's SQL Database Connection.

Source Files

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