Choose layers and time

Start with one question

Choose the layer that answers your task. Different layers can describe observations, forecasts or other reference information; matching colours or dates do not make their meanings identical.

Build a readable view

Add complexity only after the first layer is understood.

1. Choose a layer and read its source/coverage information.
2. Set its period or relevant time control before comparing features.
3. Inspect units and the legend, then add a second relevant layer if needed.
4. Check that the compared quantities and times mean the same thing.

Read the time rather than the motion

A playback or moving control does not imply that the source measures continuously. Distinguish a forecast valid time from when the forecast was produced, and an observation time from retrieval time.

When data is unavailable

Keep gaps visible. A layer outside its available time range or a failed request must not be interpreted as a measured zero. Use the information shown by the layer and retry where appropriate.

Maps guides

Learn one useful map task before exploring further.