Metro Station Prague

Metro Station Prague is an simple android app for notifying you on which Prague subway station you are. It works completely offline utilizing network cell information.

Get it on Google Play

Motivation

I was spending considerable amount of subway travel time by watching MOOC videos on my phone while having earphones. I was being constantly confused where I am. This application solved my problem by showing me where I am on phone display (where I was looking anyway).

Features

First proof-of-concept was created by riding through Prague Metro with few phones in a pocket to capture cell information for all operators. From that time application evolved, features include:

• Three types of on-display notification - Notification area, toasts and overlay (most useful for watching videos, but most intrusive).
• Predictive notifications - Phone can be quite slow to catch signal after the blackout in tunnel. Notification often arrived too late. Predictive notifications are trying to solve this problem by deducing line and direction of ride to predict next station.
• Cell logging - Anonymous cell data are sent to server and later processed to fix / add missing cells. This enables application to keep working over time as cells are sometimes changing.
• Small, battery efficient, non-obtrusive, ad-free application.

Known limitations

Application is not 100% reliable. There are few situations which can prevent application from working correctly:

• Phone sometimes skips station (does not catch signal) or does not update location on background
• Generally all places where subway goes above the ground (mostly remote parts of Metro) contain lot of cell ids. It is hard or maybe even impossible to assign them to stations, so app may not work perfectly there.
• As permanent cell signal will spread to more and more stations, there may be some other approach needed.

License and copying

This source code is released under GPLv3.

Building

Project structure

.
├── Cellar
├── MetroStation
├── Snake
└── Tracking

• Cellar - Small spring based web server for receiving data from clients.
• MetroStation - Main android application. Contains UI, settings and event retrieval code. Produces apk.
• Snake - Small quick and dirty Scala program to analyze cell data from phones. It produces "snakes" of event chains in which it is visually easy to identify problems.
• Tracking - most of the logic is here in plain java library. Involves detection of location, predictions and via api is used by main application. Tests are using Java 8 but library needs to stay at Java 7 (which may give you a little trouble in IDE).

Prerequisites:

• Oracle JDK 8
• Android SDK platform 22
• 5.2 version of ProGuard inside Android SDK folders (see below)
• Scala 2.11.7 for cell data analyzer

Release build uses proguard to obfuscate and minimize app size. Unfortunately build needs JDK8 which makes default android proguard fail. As a workaround you can put new proguard version into android-sdk/tools/proguard directory (keep default configuration files).

Running the build

Build uses Gradle wrapper or you can use Gradle 2.14. Release build of android application needs following environment variables defined for signing:

MS_KEYSTORE
MS_KEYSTORE_PASS
MS_KEY
MS_KEY_PASS

If you deploy your own cell logging server you also need to specify an url variable

MS_UPLOAD_URL

Example of invoking full build (fill in your values):

#!/bin/bash

export MS_UPLOAD_URL=http://xx.xx.xx.xx:48989/store

export MS_KEYSTORE=~/projects/keystore
export MS_KEYSTORE_PASS=keystore_password
export MS_KEY=metrostation-key
export MS_KEY_PASS=key_password

./gradlew clean build