Visibility chart card

Who it’s for

Road safety managers, airport operations teams, and port and harbor controllers ask “how has visibility changed over the selected period, and how does it compare to conditions last week?” They want the current reading, the percentage shift, and the trend curve in one card to support operational planning and incident review.

What it does

A sensor averaging 2.5 km this week versus 6.0 km last week shows an orange value — Moderate — with a -58% delta and a -3.5 km absolute change, plus a chart of readings over the selected window.

• Large current visibility value color-coded across three bands from Poor to Good
• Delta percentage and absolute delta comparing the current period to the previous one
• Time-series chart of visibility readings averaged per interval
• Shows one sensor’s data; it does not compare multiple sensors

How to set up

Data keys

Key	Role	Type	Description
visibility	Chart series	Timeseries	Atmospheric visibility distance (km); drives the chart and all derived overlays
Latest	Latest value	Timeseries	The headline figure above the chart. Its own color ranges are where the band colors are edited
Delta percent	Percentage change	Timeseries	Change against the previous period, as a percentage
Delta absolute	Absolute change	Timeseries	Change against the previous period, in the key’s own unit

The widget ships with a simulated function datasource key labeled Visibility, so it draws random values until you point the datasource at a device and rename the key.

To point it at your own device: open the dashboard in edit mode, open the widget’s Datasources, pick the entity or entity alias, and replace the function key with the key your device reports.

If the key has never reported for the selected time window, the chart is empty and all overlays show no data.

Value ranges

Range (km)	Level	Color
0–1	Poor	Red
1–4	Moderate	Orange
4+	Good	Green

How to customize

• To use your own visibility thresholds — edit the color ranges on the Latest data key; adjust the three default bands to match your operational or regulatory thresholds.
• To change the comparison period — adjust the Time window on the dashboard; the delta automatically compares to the equivalent preceding period.
• To hide or show the chart — toggle Show chart in the widget settings.
• To change the chart line color — set Chart color.
• To hide the entity name subtitle or the timestamp — turn off Show subtitle or Show date.
• To match your dashboard’s fonts — set the font options under each data key’s appearance settings.

Tips

• Poor visibility below 1 km corresponds to the ICAO threshold for low-visibility procedures at airports and is the common trigger for reduced speed limits on motorways during fog events; adjust the Poor/Moderate boundary to match your local regulation.
• The absolute delta in km is often more useful than the percentage for visibility — a drop from 10 km to 5 km is operationally less significant than a drop from 2 km to 1 km, even though both are -50%.
• Fog typically forms when visibility drops quickly overnight while relative humidity approaches 100% — pair with a humidity chart card to correlate the two signals during incident review.