Jätkäsaari Open Data Catalog

General

This document describes open data interfaces for Conveqs open data. Currently there are two ways for accessing the data: 1) connecting to the websocket interface for stream of messages, and 2) fetching the data via REST interface. Both interfaces provide similar json format (described below).

Accessing the data

REST interface

TO BE ADDED LATER

Websocket connections

Connecting to websocket server

In order to get the data stream via websocket, one has to connect to the server (jatkasaari.conveqs.fi) with wss protocol. The streams for radar data are located at wss://jatkasaari.conveqs.fi/ws/radar/json. In addition to URL one needs to set the query parameters to the URL, namely the [SUBJECT] and [TOKEN].

A full websocket request will be like:
wss://jatkasaari.conveqs.fi/ws/radar/json/?subject=[SUBJECT]&token=[TOKEN]

The streamns currently available are: Stream Type Description Note
radar.[X].objects_geo.json json Geodata [X] defines the radar id

Token is a public key, you can request from jatkasaari@conveqs.fi. An exampole code for connecting can be found in the following chapter

Sample code, Python

One can access the websocket stream for radar 1 with following code:

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""Sample client for testing the Conveqs radar data connection

This module demonstrates usage of Conveqs radar data stream by making a
connection to one radar and subscribing to geacoordinate data in json-format.
After subscriotion, the data are priunted to screen.

Example:
    $ python client.py
"""

import websocket

# Callback functions

def on_message(ws, message):
    print(message)

def on_error(ws, error):
    print(error)

def on_close(ws):
    print("### closed ###")

def on_open(ws):
    print("### closed ###")

if __name__ == "__main__":
    websocket.enableTrace(True)

    url = "wss://jatkasaari.conveqs.fi/ws/radar/json"
    subject = "radar.1.objects_geo.json"
    token = "ADD YOUR TOKEN HERE"

    wsc_url = "%s/?subject=%s&token=%s" % (url, subject, token)

    ws = websocket.WebSocketApp(
        wsc_url,
        on_message=on_message,
        on_error=on_error,
        on_close=on_close)

    ws.run_forever()

Note: in order to work, you will need a valid web-token. You can request one from jatkasaari@conveqs.fi

Data types

Radar Geocoordinate data (JSON)

General

This data includes location measurements from Smart Micro radars. The radar tracks moving objects appearing in it's beam covering up to eight lanes of traffic up to 150 meters from radar location, a typical set up can be seen in Figure 1. In addition to location, radar measures the speed and length of the object. Measurement is updated 10 times per second, and each object is tracked by assigning a uniquer id numbber for it.

In addition to location and speed vectors, accuracy information, vehicle type and lane id are provided with the data. Detailed description of the data fields are given in following chapter.

Data fields

Each message contains header fields describing the message and a list of detections and a list of objects followed by the radar

Key Type Unit Description
source string - Data source identifier
status string - Sender status message
tstamp int Unix time
nobjects int count Number of objects in message

After the header there is a list of detections containing following fields:

Key Type Unit Description
lat float Degrees Latitude gegrees
lon float Degrees Longitude degrees
v_n float m/s Speed towards north
v_e float m/s Speed towards west[?]
len float meters Length of the object
id int - Internal id-number cycles from 0 to 254
lane int lane id Lane id number
class int object type Object type determined by the radar *)
cyc_ago int - Number of cycles since last detection
quality float percentage Detection quality determined by the radar

Sample data

{
    "source": "radar.1.objects_geo.json",
    "status": "OK",
    "tstamp": 1601279853465,
    "nobjects": 1,
    "objects_geo": [
        {
            "lat": 60.16093739873581,
            "lon": 24.92177615985368,
            "v_n": -1.05,
            "v_e": -0.25,
            "len": 1.0,
            "id": 137,
            "lane": 0,
            "class": 1,
            "cyc_ago": 3,
            "quality": 58.82
        }
    ]
}

JSON Schema

The schema fo this data type can be found here

Vehicle Trip data (JSON)

TO BE ADDED LATER

LOS data

TO BE ADDED LATER

More information

For more information, please contact jatkasaari@conveqs.fi