ElevatorstatePublicTransportHamburg

API for monitoring state of elevators in Hamburg. It is useful for wheelchair users and Mutties.

Data sources

What we need:

Actual state informations for sending push notifications to device and we need real coordinates of elevators. Unfortunatally there is no public API. What we have:

Coordinates from OSM and actual data from geofox. But there is no reference between. gfxId is no part of overpass entry.

Live request from geofox

On this Geofox page we can get retreive realtimne data. Unfortunatelly the lat/lon position are fictional and only for this special map. An example response can find here

{
		"gfxId": "Master:11950",
		"lon": -92.1464,
		"lat": -208.9392,
		"elevators": {
			"A": {
				"state": 1,
				"description": "Zugang Alsterpavillion <-> Schalterhalle",
				"label": "A",
				"type": "DURCHLADER",
				"tasterType": "KOMBI",
				"lines": [],
				"cabinLength": 0,
				"cabinWidth": 0,
				"doorWidth": 0,
				"instCause": ""
			},
			"B": {
				"state": 1,
				"description": "Schalterhalle <-> Zwischenebene (U2,U4)",
				"label": "B",
				"type": "DURCHLADER",
				"tasterType": "KOMBI",
				"lines": [],
				"cabinLength": 0,
				"cabinWidth": 0,
				"doorWidth": 0,
				"instCause": ""
			}
		},
		"mainSubStation": {
			"linkId": "Master_11950",
			"stationName": "Jungfernstieg S1/S2/S3/U1",
			"comment": "Haltestelle nicht barrierefrei"
		},
		"additionalSubStations": {
			"Master_11950_U": {
				"linkId": "Master_11950_U",
				"stationName": "Jungfernstieg U2",
				"lineKeys": ["HHA-U:U2_HHA-U_HHA-R"],
				"comment": "Einstieg für Rollstuhlfahrer im gekennzeichneten Bereich"
			}
		}
	}

This data renders this map:

Overpass

Overpass is a protocol to request data from OSM.

With it we can ask the database of OSM with this request:

[out:json];
area[name="Hamburg"];
(
  node["highway"="elevator"](area);
  way["highway"="elevator"](area);
  relation["highway"="elevator"](area);
);
out body;
>;
out skel qt;
(._;>;);out;

and get i.e.

{
  "type": "node",
  "id": 430136424,
  "lat": 53.5531786,
  "lon": 9.9936662,
  "tags": {
    "description": "Straße/Schalterhalle",
    "entrance": "yes",
    "entrance_marker:s-train": "yes",
    "entrance_marker:subway": "yes",
    "entrance_name": "Jungfernstieg",
    "highway": "elevator",
    "manufacturer": "Lutz- Aufzüge",
    "name": "Jungfernstieg",
    "operator": "HOCHBAHN",
    "railway": "subway_entrance",
    "ref": "10909",
    "since": "2006",
    "toilets:wheelchair": "yes",
    "tunnelsystem_jungfernstieg": "eingang",
    "wheelchair": "yes",
    "wheelchair:description": "Aufzug vom Jungfernstieg nach unten: Rolli-WC ohne Euroschlüssel- aber Toilettenpersonal bis 22:30"
  }
},

This data renders this map:

Server for sending notifications

The nodeJS realized server has three tasks

Subscribe/unsubscribe devices

For this run a http-server with endpoints

• /subscribe?token=TOKEN and
• /unsubscribe?token=TOKEN.

Both methods persist the tokens in a local sqlite database

Fetch data from geofox and detecting changes

A simple periodically request retreives the JSON, extracts the states, saves in an array and in next step compares with lastest ones. Is there a diff then the push sender will started

Sending notification to devices

The method get all deviceTokens from local database and sends all notifications.

Android App

The app subscribes to server app and receives notifications. In main view is a google map to show current states. In a second tab is a list of elevators, sorted by distance to it.