entity_change

ai.greenlandai/greenlandai · Verify this server

change(site, t0, t1) — the STRUCTURED CHANGE between two dated frames of one site (entity_type + id, or lat + lng): per class (water · ice · canopy · pad · stockpile · unknown) the area in m², by_sensor_m2 {optical, radar}, `said` (what each instrument saw: an area, "saw no change", "makes no call", or "untestable (reason)"), sensors_agreed, and a `confidence` from agreement with `confidence_why`: high = optical and radar both flag it in the same place; medium = one flags it and the other is blind to the class or untestable; low = they disagree (different places, or one flags it and the other could see it and saw none), or stockpile, or pad/stockpile without a terrain check. Optical is Sentinel-2; Landsat only for a date with no Sentinel-2 (before 2015-06-23 or a gap); radar is Sentinel-1 (from 2014-10). A Copernicus DEM terrain prior removes pad and stockpile on ground steeper than 12° (reported as steep_ground_excluded_m2). A stockpile carries a `volume` block: the height of material above the Copernicus DEM (2011–2015) inside it, MEASURED at each date from a dated height source (USGS 3DEP lidar in the US, Canada's HRDEM lidar by acquisition project in Canada, else NASA ICESat-2 profiles via SlideRule), bias-corrected on stable ground, volume = mean height × area ± its uncertainty; when BOTH dates are lidar surfaces the change is their DIRECT DIFFERENCE, so the 2011–2015 reference and its error cancel (`change_method` says which; `change_beyond_uncertainty` = |change| > 2σ), and a confidence — or untestable with what was tried (then brightness and shape only, low). Not a video and not a picture — fetch stills with look_at / look_through. For spans of 300+ days the t0 frame is taken at t1's day of year (same_season=true, default). A sensor that cannot see the pair says UNTESTABLE with its reason; the answer is UNTESTABLE only when BOTH are. Footprint: the site's held footprint, else a 500 m circle (stated in `footprint`); radius_m 50..2500 overrides. An entity whose coordinates are only a country centre is refused (409, not charged) — pass lat + lng. Dates YYYY-MM-DD, t0 on/after 1984-03-16, t1 default today. Slow: about 15–60 s. AGENT KEYS ONLY (a browser session is refused BEFORE any charge). SIDE EFFECTS: none beyond the charge — read-only. ⚠ CHARGING: ONE quote, ONE debit = two stills at look_at's live price, reserved up front; an UNTESTABLE answer costs nothing. Quote with `billing_quote("/api/v1/entity.change")`; the JSON carries `charged_joules` and a `price` block.