tiling

The tiling module converts a propagated ground track into a series of overlapping geographic download boxes, each with an associated time window. These boxes are the unit of work for the download stage.

The core design decision here is that boxes are defined in along-track chunks rather than as a global region. This keeps each FDSN query geographically small, which is much faster and avoids querying stations that are nowhere near the track.

Boxes overlap by overlap_km (default 50 km) to ensure stations near the boundary between adjacent boxes get picked up by at least one box. Each box also gets a time window padded by pre_pad_minutes before and post_pad_minutes after the segment’s actual track times, to capture waveform arrivals that occur slightly before or after the object passes overhead.