geolocation.el

Get your location on Earth.

Description

This package obtains your current location by obtaining the MAC addresses of nearby wifi access points and then submitting that list to third-party geolocation APIs. Those geolocation services use the known locations of the wifi access points and the relative strength of each signal to triangulate your latitude and longitude.

Entry points

• geolocation-update-position which calls geolocation-get-position on a regular interval, and sets geolocation-location with the result. Calls the geolocation-update-hook functions after each update. Customize the hook if you want to invoke functions based on your position, and customize the geolocation-update-interval with the time granularity you need, keeping in mind the underlying positioning APIs may have rate limits and/or costs associated with high frequency querying.

  The variable geolocation-location will contain nil or an alist:

  • latitude - latitude of the current position
  • longitude - longitude of the current position
  • accuracy - an error radius, in meters
  • timestamp - timestamp via float-time

Other potentially useful functions include:

• geolocation-get-position which retrieves your estimated position once and invokes a callback with the position data. The callback receives an alist with the same format as geolocation-location.

• geolocation-scan-wifi which scans asynchronously for nearby wifi access points using available system utilites, and invokes a callback with the wifi data. The callback receives a list of alists containing:

  • bssid - mac address that uniquely identifies the AP
  • signal - relative signal strength, or RSSI
  • channel - transmission channel

• geolocation-update-calendar stores the latest position in calendar-latitude and calendar-longitude. This function works as a geolocation-update-hook.

At present, wifi scanning is supported on Mac OSX and Windows. Linux support is planned but not yet implemented.

Geolocation services

You have a choice of third party services to use for the positioning:

• Google Maps Geolocation API
• HERE Technologies Positioning API
• Unwired Labs Location API

This package offers a set of customizable variables you can use to select which service is used, declare your API access token, choose the nearest API endpoint, and so on. Those settings can be found in M-x customize, then browse for "Environment", then "hardware", and then "Geolocation".

By default, access tokens are expected to be accessed via the built-in auth-source package. You can configure any backend, as this package only requires the token to be searchable via auth-source-pick-first-password.

Rate Limits and Costs

Each of these services requires you to create your own account, and potentially provide billing information as well. You will be agreeing to the vendor's end-user agreements including such things as acceptable usage policies and privacy terms, when you create your account.

Care has been taken to choose services that include either a free tier, or equivalently, an allowance of a certain amount of usage per day or per month. It's your responsibility to set up your account with those services, obtain and protect your token, and manage your usage of those APIs because there can be associated costs if your usage exceeds the usage terms of the subscription or plan you choose.

WARNING: THIS PACKAGE COLLECTS INFORMATION THAT IMPLIES YOUR PHYSICAL LOCATION. THAT DATA WILL BE SENT TO THIRD-PARTY GEOLOCATION SERVICES WHICH CAN PINPOINT YOUR LOCATION TYPICALLY WITHIN 100 METERS OR LESS. WHILE THIS PACKAGE DOES NOT ITSELF STORE YOUR LOCATION, WE CANNOT GUARANTEE WHAT A GIVEN THIRD-PARTY SERVICE MAY DO WITH THE DATA IT RECEIVES IN THESE API TRANSACTIONS. RATHER, YOU UNDERSTAND AND AGREE TO THE PRIVACY AGREEMENTS AND END USER AGREEMENTS OF EACH OF THE INDIVIDUAL GEOLOCATION APIS YOU USE.

Documentation

Obtaining the API token

Choose one of the following services and follow the corresponding link. In each case you're going to have to create a developer account with the company subject to the service's pricing and terms.

You only need one of the following:

• Google Maps Geolocation API
• HERE Technologies Positioning API
• Unwired Labs Location API

Once you have an account, you will be able to generate an API token. Copy down that token (it's typically a long string of numbers and letters) and store it somewhere safe (see next section).

Protecting your token using auth-sources

The idea here is to configure auth-sources and select a backend for your passwords to be stored. Assuming you use a GnuPG encrypted file named ~/.authinfo.gpg then that file needs to contain a line like this:

machine googleapis.com user geolocation.el password "#############"

The password field must contain the token you obtained when you created your account. The machine and user fields must match the values of the corresponding customizable variables described below, and if you're in doubt, the default user and hostname will be fine.

See the article "Keeping Secrets in Emacs with GnuPG and Auth Sources" for detailed information about using the auth-sources library.

Configuration settings

To configure the package use M-x customize and browse to "Environment" then "Hardware" and finally "Geolocation".

You will need to customize geolocation-api-vendor to select the service you want to use. Accepted values are :google (default), :here and :unwiredlabs.

Then you need to set the host and usernames so this library can find your token in auth-sources. Those are:

• Google
  • geolocation-api-google-auth-source-host (default is "googleapis.com")
  • geolocation-api-google-auth-source-user (default "geolocation.el")
• HERE
  • geolocation-api-here-auth-source-host (default "pos.ls.hereapi.com")
  • geolocation-api-here-auth-source-user (default "geolocation.el")
• Unwired Labs
  • geolocation-api-unwiredlabs-auth-source-host (default "unwiredlabs.com")
  • geolocation-api-unwiredlabs-auth-source-user (default "geolocation.el")

In ordinary situations you won't need to customize anything else.

Changelog:

• First snapshot released to MELPA ({include date when released})
  • Scan wifi access points using available system utilities
    • OSX: use the "airport" utility
    • Windows: use "netsh wlan show networks"
    • Linux: not yet implemented
  • Get geolocation via third party APIs (Google, HERE, and Unwired Labs)

Copyright

Copyright (C) 2020 Neil Okamoto neil.okamoto+melpa@gmail.com.