Could You Build a Small Dashboard Coverage Map?
From the earlier reference collection. Read the current software blog.
A coverage map plots configured station locations and states clearly when those locations and their underlying data were last updated.
Define what coverage means
A map can show where a dashboard knows about stations, but a marker alone does not say whether a station is active, reporting, or recently observed. Define coverage as a specific property before drawing anything. For a first version, it might mean that a station has a configured latitude and longitude and is included in the dashboard’s source list. Keep this distinct from current sensor availability.
Give the map a date that describes its input. If station locations came from a configuration file updated on a particular day, label that date as the location data date. If observation freshness is also shown, label it separately. A single vague “updated” timestamp can mislead readers into thinking every station has recently reported.
Prepare and validate station data
Represent each station with a stable identifier, a display name, coordinates, and any status needed by the page. Validate that coordinates are numeric and fall within valid latitude and longitude ranges before plotting. Missing or invalid locations should appear in a small count or list outside the map, not disappear without explanation.
For example, a station record might contain identifier north-pier, name North Pier, latitude 37.8, and longitude -122.4. Those numbers are illustrative fixture values, not a claim about a real station. Keep the identifier available in the marker’s accessible label and detail view so that two locations with similar names remain distinguishable.
Draw a readable view
For a compact dashboard, a static map or a simple coordinate plot may be enough. Choose a view that fits the geographic spread: a city-wide set of points can be shown at a useful local scale, while widely distributed points need a broader extent. Avoid hiding nearby stations behind a single marker; clustering or a list view can help when points overlap.
Use more than color to encode status. A different shape, outline, or text label can distinguish a station with recent data from one with no current observation, if those states are available. Provide a legend that defines each symbol and a text alternative listing station names and statuses. The map should remain understandable to someone who cannot perceive its colors or interact with a pointer.
Make coverage verifiable
Place the coverage date near the map title and say what it applies to, such as “Station locations checked on…” Include the number of configured stations and, if useful, the number with valid coordinates. These counts help a reader notice an unexpectedly empty or partial display without guessing from the map.
Test the page with zero stations, one station, several overlapping points, an invalid coordinate, and a stale location file. A zero-data state should explain whether no stations are configured or the source could not be loaded. A useful coverage map is a compact statement about the reach and limits of the dashboard; its labels and date are part of the data, not decorative details.