Radar SwiftUI Screen

The radar is drawn like a signboard: a fixed lattice of dots over the map, where each dot's size and colour are the rain beneath it. Dry land is a field of faint dots, the sea fainter still, with the coast as a hairline and towns labelled in small capitals. Press play and the band of showers crosses the coast frame by frame, the dots swelling and fading between frames instead of jumping. The title's second line is the nowcast for where you are ("Rain from 15:40"), read from the same frames.

Pinch to zoom and the lattice stays fine, so zooming resolves the storm rather than enlarging dots; drag to pan once zoomed, double-tap to see everything, or use the locate button to jump to your position and back. The timeline below carries a tick per frame and the frame's time on its thumb, the legend is four colour blocks from light to severe, and alerts run along a strip under the map.

Notes

• Feed DotRadar an array of RadarFrames: a grid of intensities per time step, from your radar provider or a nowcast model. position is a fractional frame index; animate it and the field blends between neighbouring frames.
• Land is a set of polygons in map coordinates. Their edges, less any that run along the map's border, become the coastline, so one shape gives you both the land dots and the hairline.
• Levels and thresholds come in through DotRadarStyle. The example takes four of the scheme's blocks, from light to severe, so every preset brings its own ramp.
• VoiceOver reads the radar as one element with a summary you supply, supports the zoom rotor action, and adjusts DotRadarTimeline frame by frame.
• Reduce Motion keeps playback (it is information) but steps between frames without the blend and stops the ticker on the first alert.
• DotRadarExample at the end of DotRadar.swift is the screen shown in the preview; copy it as a starting point.