Description of datasets
Short description of each dataset, including how you should interpret the content of the tiles for each dataset.
wind
Global forecast of wind intensity in meters pr. second for the next 2-3 days. Usually updated with a new version every 6 hours.
The RGB values in a pixel represent:
- R: Wind X component, as actual X component (wind speed*2) + 128. This means that the value 129 gives an eastward wind component of 0.5 m/s, and 125 gives a westward wind component of 1.5 m/s.
- G: Wind Y component. Same value scheme as for wind X component, but a value less than 128 gives a southward wind component, but greater gives a northward component.
- B: Unused.
NOTE: eastward means wind blows towards east.
In a map presentation you will then usually want to calculate wind speed and/or wind direction from these component values using normal trigonometric calculations.
precipitation-nowcast
Forecast of precipitation intensity in mm pr. hour for the next 90 minutes for Norway, Denmark, Sweden and Finland. Usually updated with a new version every 5 minutes.
Each pixel value represents a color, as in a regular image. The table below lists all possible color values in this dataset, and a description of what each color represents.
| Color in hexadecimal | Precipitation intensity in mm/h |
|---|---|
| #FFFFFF | No data for this area |
| #000000 | x < 0.03, in practice no precipitation |
| #91E4FF | 0.03 <= x < 0.05 |
| #5ED7FF | 0.05 <= x < 0.2 |
| #00AAFF | 0.2 <= x < 1 |
| #0080FF | 1 <= x < 5 |
| #0055FF | 5 <= x < 15 |
| #7A0087 | 15 <= x |
precipitation-observations
Historical timeseries of precipitation intensity in mm pr. hour for the previous 90 minutes for Norway, Denmark, Sweden and Finland. Usually updated with a new version every 5 minutes.
The pixel content is identical to precipitation-nowcast.
precipitation-amount
Global forecast of precipication intensity in mm pr. hour for the next 2-3 days. Usually updated every 6 hours.
The pixel content is identical to precipitation-nowcast.
air-temperature
Global forecast of air temperature in celsius for the next 2-3 days. Usually updated with a new version every 6 hours.
The RGB values in a pixel represent:
- R: Temperature in celsius is: red value - 128.
- G: Unused.
- B: Unused.
cloud-area-fraction
Global forecast of cloudiness in percent for the next 2-3 days. Usually updated with a new version every 6 hours.
The RGB values in a pixel represent:
- R: Percentage of cloudiness. Values go from 0-200, each increment representing 0.5 percent.
- G: Unused
- B: Unused
Glossary
Dataset
Each dataset distributed by this WebAPI contains a set of tiles for a weather parameter for each timestep in the dataset. The dataset is based on one or more data sources. The data sources are typically observations or weather and ocean forecast models.
Each dataset is updated when the data sources are updated, which happens regularly, but at different frequences for each dataset. E.g precipitation-nowcastis updated every 5 minutes.
Each update creates a new version of the dataset. Each version is identified by a uuid. Each version of the dataset contains a set of tiles for each timestep.
When a dataset gets updated with a new version, the tiles from the superseded version will be available for some time (varies by dataset, but at least 45 minutes).
Timestep
Meteorological data is often represented as a timeseries, e.g the weather forecast for a specific place for the next 3 days. The datasets from this service is no different.
Each version of a dataset has a tileset for each timestep. So, typically when a mapping client library asks you to configure a raster layer or raster tiles or similar, its the same as the tileset for a specific timestep in our service.
Tiles
Tiles are a style of maps, where the world is divided into squares, the number of squares needed to cover the earth increases as the zoom level increases.
Usually these tiles are either vector data or raster data, meant to be presented as a geographical information in a web application in the WebMercator projection.
The tiles from this WebAPI however, contains meteorological or oceanographica data, either coded as colors or as numerical data that must be transformed into a coloring scheme to be useful in a visual presentation.
Read more about tiles at https://en.wikipedia.org/wiki/Tiled_web_map
Tileset
A set of urls that represents a raster map layer. Each specific url downloads a tile in the set.
Typically represented with an url template, like: http://example.com/api/example/{z}/{x}/{y}.webp.
Tiling scheme
A WebAPI that delivers tiles must have a specific scheme for how it divides up the world in squares. There are 2-3 different popular schemes for how this is done. Our WebAPI use the xyz/Slippy map scheme
Layer
A map can include multiple types of information that can be accessed separately and visualised together. This is usually called layers. In relation to tiles, one raster tileset becomes one map layer. E.g a tileset for a single timestep of a single version of the dataset wind is a map layer.
WebGL
WebGL is a javascript API for rendering graphics in the browser. The API and the concepts used closely conforms to OpenGL.