Module 2 › Lesson 7

Mobile GIS

Table of Contents

Terms: location awareness, geolocation API, location-based service, geofencing, volunteered geographic information (VGI)

Introduction

A map that knows where it is. This sounds like something from the realm of fantasy—enter the magic passcode to unlock the map, and it will reveal to whomever holds it their current location on the very map they are holding. This is the reality that has been made possible by portable, location-aware electronics.

The popularity of smartphones has implications for how web maps look and work. They have smaller screens and different input methods with which to interact with maps, which could be seen as shortcomings to those used to designing for monitors, a mouse, and keyboard. But phones also allow people to become part of the map, opening up new possibilities for Web GIS. From Uber to Pokemon Go to Tinder, Web GIS is a common feature in mobile applications.

Location awareness

As the name implies, mobile devices move. Moreover, smartphones can know where they are, if they are moving and at what speed, and which direction they are facing. This ability to determine location is called location awareness. A device can be aware of its position on Earth using GPS satellites, cell tower triangulation, proximity to known Wi-Fi networks, or a combination of these and other methods.

GPS chips in smartphones allow the device to calculate its location within several meters without the need for cellular service or the Internet. Disable your Wi-Fi and cell service (airplane mode) and your phone will still give you a reasonably accurate latitude and longitude, because the GPS chip is still receiving signals from GPS satellites and calculating the location based on those signals, although it will not be as accurate as when your device can use the Internet to communicate with a geolocation service.

Geolocation API

A geolocation API allows applications to improve their location awareness by transmitting the device’s location data to a third party over the Internet (via a web service). The service compares the location data with databases of network devices for any information that might give clues about the device’s true location. Is the device close to a known Starbucks Wi-Fi, or a bluetooth beacon at GameStop?

The web service response is a new location with the estimated accuracy. Android apps will probably use Google’s geolocation service, while iOS apps might use Apple’s.

The World Wide Web Consortium (W3C) released a technical standard for a geolocation API. It provides a method for browsers and applications to use a location service.

The JavaScript code that would be added to a webpage or app can be as simple as:

navigator.geolocation.getCurrentPosition(function(pos){
  alert(pos.coords.latitude + ',' + pos.coords.longitude)
})

When you click the blue button, your browser will first ask for permission to use your location. Then it will collect whatever information it can about your device’s location, send it to the geolocation service, and then display a popup with the latitude and longitude.

If you are not on a mobile device, then the only information your browser will send will likely be your IP address, which will not give an accurate location. But if you are on a phone, the coordinates should be pretty close. When I try on LSU’s campus using a device with only GPS and Wi-Fi, the service usually locates me in the correct classroom, on the correct side of the room.

Location-based services

Instead of making a window pop up like in the example above, applications can send your location off to another application to provide some kind of functionality or information to you. This is a location-based service (LBS). Uber and any other app that relies on your location can be considered LBS. You can probably find many more examples by going into your phone’s privacy settings to see which apps have or would like permission to use your location. Go ahead, check.

“Input” into computer programs in the traditional sense involves things like clicking, scrolling, typing, tapping, and swiping. These inputs, known as “events”, trigger a response from the program. But with LBS, your movement, and the resulting change in location, can itself become an input. When your movement into or out of a certain area triggers a reaction from a location-based service, this is called geofencing.

Volunteered Geographic Information

The widespread use of location-aware devices has turned people into sensors, collecting data and transmitting it over the web almost constantly, even when not actively using a phone. This has become a new source of geographic information.

Volunteered geographic information (VGI) is crowd-sourced contributions of content with a location attribute. It is an alternative to authoritative data sources from governments or businesses. VGI is an evolution of Web 2.0, which has seen the rise of crowd-sourced platforms that depend on user-submitted content, such as Wikipedia, Youtube, and Facebook. VGI is especially useful for endeavors that are too large in scale or are changing too rapidly to be monitored by a smaller team of people.

VGI has been used in response to wildfires, with citizens reporting on the quickly spreading perimeter through web-based maps.

Road networks are huge complex systems with constantly changing conditions, making them a prime use-case for VGI. Waze is an app that allows users to submit traffic and travel information such as crashes and police speed traps. Google uses location data from Android phones and Google apps, recording not just location but speed, to determine traffic flow and calculate travel times and routes. (However, are users aware that they are “volunteering”?)

When Malaysia Airlines Flight 370 disappeared in 2014, millions of amateurs pored over satellite imagery to search for remnants of the aircraft in a crowd-sourcing effort organized by imagery provider Digital Globe. In this case, the information the crowd submitted was not the imagery itself but an attribute for the location of the image: whether or not it potentially contained wreckage.

The City of New Orleans manages 72,000 catch basins for street drainage. Each one is mapped on the Adopt-A-Catchbasin web GIS application that allows citizens to report whether drains are clear or clogged, and even “adopt” a catch basin to take responsibility for keeping the rainwater flowing out of their street.

Crowd-sourced information raises questions of accuracy. It can be difficult to verify user submissions, making the platforms more susceptible to mistakes and vandalism than traditional authoritative data sources.

Summary

Location-awareness is now a defining characteristic of smartphones. Where desktop GIS brought maps to people, mobile GIS brings people to maps, making user locations the core aspect of some apps. Mobile GIS has spawned new apps and entire industries—would the rideshare industry exist without location-aware mobile devices and mapping applications? It has also raised new concerns for privacy and governance—aren’t citizens with trackers and identifiers a favorite dystopian trope?

End of Module Questions

Think back on the lessons on data formats, standards, mobile GIS, and considerations for making web-based maps. Relate the concepts to the assignments.

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