Graham McIntire
d67186176f
Type spec fixes: - duct_usable_* return boolean→float (delegate to duct_usable_for_band) - sanitize/1 spec includes :unicode error tuples - match_delete/1 broadened from :ets.match_spec() - telemetry_event local type replaces :telemetry.event/0 - wgrib2 parse_lon_val_segment corrected to tuple spec - preloaded Ecto assoc types in get_mission/get_contact! specs Unmatched returns: - _ = prefix on Task.start, Oban.insert, Repo.query!, PubSub.subscribe, :ets.new, and if-expression returns across 18 files Pattern match fixes: - markdown: restructure acc!=[] guard as direct pattern match - path_compute/pskr/skewt_location_resolver: remove dead clauses - calibrate.aprs_144: remove unreachable format_float catch-all - unused.ex: suppress MapSet.union no_opaque Also: remove unused unicode_util_compat from mix.lock
79 lines
2.5 KiB
Elixir
79 lines
2.5 KiB
Elixir
defmodule Microwaveprop.Buildings.Parser do
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@moduledoc """
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Streaming parser for Microsoft Building Footprint csv.gz tiles.
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Each line is a GeoJSON `Feature` whose `geometry.coordinates` is a
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Polygon (or MultiPolygon) and whose `properties.height` is meters
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above ground. We collapse each polygon to a centroid + bounding
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radius — that's all the rover path-clearance scorer needs, and it
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keeps the in-memory footprint to ~32 bytes per building.
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Polygons with `height = -1.0` (no estimate from the ML model) are
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dropped — including them would just add noise.
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"""
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@type building_record :: %{
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centroid_lat: float(),
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centroid_lon: float(),
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max_radius_m: float(),
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height_m: float()
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}
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@doc """
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Returns a `Stream` of `t:building_record/0` for every polygon in `path` whose
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height is known. Lazy; suitable for tiles with millions of rows.
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"""
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@dialyzer {:no_return, parse_tile: 1}
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def parse_tile(path) do
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path
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|> File.stream!([:read, :compressed])
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|> Stream.flat_map(&parse_line/1)
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end
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defp parse_line(line) do
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case Jason.decode(String.trim(line)) do
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{:ok, %{"properties" => %{"height" => h}, "geometry" => geom}} when h > 0.0 ->
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case ring_from_geometry(geom) do
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[] -> []
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ring -> [build_record(ring, h)]
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end
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_ ->
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[]
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end
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end
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defp ring_from_geometry(%{"type" => "Polygon", "coordinates" => [outer | _]}), do: outer
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defp ring_from_geometry(%{"type" => "MultiPolygon", "coordinates" => [[outer | _] | _]}), do: outer
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defp ring_from_geometry(_), do: []
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defp build_record(ring, height) do
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{sum_lat, sum_lon, n, min_lat, min_lon, max_lat, max_lon} =
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Enum.reduce(ring, {0.0, 0.0, 0, 90.0, 180.0, -90.0, -180.0}, fn
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[lon, lat], {sl, slon, n, mnla, mnlo, mxla, mxlo} ->
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{
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sl + lat,
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slon + lon,
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n + 1,
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min(mnla, lat),
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min(mnlo, lon),
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max(mxla, lat),
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max(mxlo, lon)
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}
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end)
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centroid_lat = sum_lat / n
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centroid_lon = sum_lon / n
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# Approximate max radius: half-diagonal of the bbox in meters.
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dlat_m = (max_lat - min_lat) * 111_000.0 / 2.0
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dlon_m = (max_lon - min_lon) * 111_000.0 * :math.cos(centroid_lat * :math.pi() / 180.0) / 2.0
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%{
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centroid_lat: centroid_lat,
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centroid_lon: centroid_lon,
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max_radius_m: :math.sqrt(dlat_m * dlat_m + dlon_m * dlon_m),
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height_m: height * 1.0
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}
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end
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end
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