Occupancy Display

Processes and displays occupancy numbers / visitor counts.

Configuration

config.template can be used as a starting point for creating the configuration file config.json.

Configuration file

{
  "areas": {
    "area1": {
      "name": "area1",
      "capacity": 360,
      "factor": 0.68,
      "inputs": ["Area1"]
    }
  },
  "limits": {
    "green": {
      "threshold": 0,
      "image": "img/green_lights.png"
    },
    "yellow": {
      "threshold": 91,
      "image": "img/yellow_lights.png"
    },
    "red": {
      "threshold": 96,
      "image": "img/red_lights.png"
    }
  },
  "datafile": "input_file",
  "texts": {
    "en": {
      "tooltip": "percent % of capacity seats in total are occupied",
      "nodata": "Temporarily no data available",
      "closed": "No seats available"
    },
    "de": {
      "tooltip": "percent % von capacity Arbeitsplätzen sind belegt",
      "nodata": "Momentan keine Daten verfügbar",
      "closed": "Keine Arbeitsplätze vorhanden"
    }
  }
}

Field	Description
areas	Dictionary of areas, i.e. identified by id and display name area1. Additional parameters are the capacity for visitors, a correction factor and an array of inputs. state can be specified in order to set the display fixed to closed or nodata.
limits	Dictionary of states, i.e. green, yellow and red. The
datafile	Path to the input data file. Expected content: input1:n1 input2:n2 ....
texts	Dictionary of display texts for languages en and de. tooltip, nodata and closed.

Webserver configuration

The main script index.php is located in the subdirectory htdocs.

Example for Apache:

Alias "/occupancy" /var/www/occupancy-display/htdocs

Development using docker / podman

For local development and testing, a temporary webserver can be started using docker or podman:

# Start temporary webserver, stop with ctrl-c.
docker run --rm -p 8080:80 --name occupancy-display -v "$PWD":/var/www/html php:8.2-apache

The display can be accessed at http://localhost:8080/htdocs.

Usage

When called without parameters, the web interface shows a table of all configured areas, by default in German.

The output can be configured using the following parameters:

• area: valid values are any of the configured area ids. If omitted, all configured areas are shown.
• lang: valid values are en and de. If omitted, de is used.
• output: valid values are json. If omitted, HTML output is shown.

Examples

• Print JSON output: http://localhost:8080/htdocs/?output=json
• Show area1 as english HTML output: http://localhost:8080/htdocs/?area=area1&lang=en

Example output

After copying config.template to config.json and creating an input_file with contents Area1:100, calling http://localhost:8080/htdocs/?output=json&lang=en produces the following output:

{
  "lastupdated": "2024-08-20, 5:04 pm",
  "texts": {
    "tooltip": "percent % of capacity seats in total are occupied",
    "nodata": "Temporarily no data available",
    "closed": "No seats available"
  },
  "areas": {
    "area1": {
      "name": "area1",
      "capacity": 360,
      "percent": 41,
      "state": "green"
    }
  }
}

Updating the input file

For real-time monitoring the occupancy, the input file has to be updated in regular intervals. Depending on the environment, different approaches are possible:

• a cgi script for updating the input file externally
• a cron job pulling the necessary information

Real world example

This software is used to feed the seat occupancy display of the Mannheim University Library.