Graham McIntire
4f647e7894
Adds Microwaveprop.Canopy module that reads 1° × 1° uint8 per-degree
canopy-height tiles (mirrors SRTM .hgt naming/layout, 30 m resolution).
Returns 0 m for areas with no tile on disk so the lookup is safe to
thread through the existing path-clearance pipeline before any data
lands.
Wires canopy into:
- PathTerrain.obstacle_top: per-sample blocker = ground +
max(building_m, canopy_m), so the rover ranks paths through forests
as obstructed even when no buildings sit on the line
- CandidateDetail profile: each sample now carries canopy_m alongside
building_m
- Rover-detail SVG: green "trees" polygon stacked on terrain, under
the red building polygon
- Path calculator elevation chart: green Tree Canopy dataset between
terrain and buildings
Data prep (download Potapov 2019 / Lang 2022 GeoTIFF, slice to per-degree
uint8 tiles, drop in /data/canopy/) is a separate one-shot operation —
without tiles, lookups return 0 and the existing behavior is unchanged.
99 lines
3.1 KiB
Elixir
99 lines
3.1 KiB
Elixir
defmodule Microwaveprop.Canopy do
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@moduledoc """
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Tree-canopy heights from a 30 m global canopy-height grid (Potapov et al.
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2019, Lang et al. 2022, or any source able to produce 1° × 1° uint8
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per-pixel rasters).
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Tile format: `@samples × @samples` bytes, row 0 at the north edge,
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one byte per pixel = canopy height in meters (0–255). Filename
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`N{lat}W{lon}.canopy` mirrors the SRTM `.hgt` convention.
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Returns 0 m for points without a tile on disk so the lookup can be
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threaded through the path-clearance pipeline without raising on
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un-fetched areas (treat unknown as treeless).
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"""
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require Logger
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@samples 3600
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@spec tile_filename(float(), float()) :: String.t()
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def tile_filename(lat, lon) do
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lat_floor = floor(lat)
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lon_floor = floor(lon)
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lat_prefix = if lat_floor >= 0, do: "N", else: "S"
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lon_prefix = if lon_floor >= 0, do: "E", else: "W"
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lat_str = lat_floor |> abs() |> Integer.to_string() |> String.pad_leading(2, "0")
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lon_str = lon_floor |> abs() |> Integer.to_string() |> String.pad_leading(3, "0")
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"#{lat_prefix}#{lat_str}#{lon_prefix}#{lon_str}.canopy"
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end
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@doc """
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Returns the canopy height in meters at `lat, lon`, or 0 if no tile is
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on disk for that 1° square.
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"""
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@spec lookup(float(), float(), String.t(), keyword()) :: non_neg_integer()
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def lookup(lat, lon, tiles_dir \\ default_dir(), opts \\ []) do
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samples = Keyword.get(opts, :samples, @samples)
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path = Path.join(tiles_dir, tile_filename(lat, lon))
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case :file.open(path, [:read, :binary, :raw]) do
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{:ok, fd} ->
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result = read_height(fd, lat, lon, samples)
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_ = :file.close(fd)
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result
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{:error, _} ->
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0
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end
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end
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@doc """
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Batch lookup. Groups points by tile so each tile is opened once.
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Returns `%{ {lat, lon} => height_m }`. Missing tiles yield 0.
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"""
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@spec lookup_many([{float(), float()}], String.t(), keyword()) ::
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%{{float(), float()} => non_neg_integer()}
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def lookup_many(points, tiles_dir \\ default_dir(), opts \\ []) do
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samples = Keyword.get(opts, :samples, @samples)
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points
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|> Enum.group_by(fn {lat, lon} -> {floor(lat), floor(lon)} end)
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|> Enum.flat_map(fn {_tile_key, pts} -> read_tile_points(pts, tiles_dir, samples) end)
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|> Map.new()
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end
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defp read_tile_points([{lat0, lon0} | _] = pts, tiles_dir, samples) do
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path = Path.join(tiles_dir, tile_filename(lat0, lon0))
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case :file.open(path, [:read, :binary, :raw]) do
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{:ok, fd} ->
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result =
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Enum.map(pts, fn {lat, lon} = pt -> {pt, read_height(fd, lat, lon, samples)} end)
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_ = :file.close(fd)
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result
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{:error, _} ->
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Enum.map(pts, fn pt -> {pt, 0} end)
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end
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end
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defp read_height(fd, lat, lon, samples) do
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row = round((floor(lat) + 1 - lat) * (samples - 1))
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col = round((lon - floor(lon)) * (samples - 1))
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offset = row * samples + col
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case :file.pread(fd, offset, 1) do
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{:ok, <<h::unsigned-integer-size(8)>>} -> h
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_ -> 0
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end
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end
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defp default_dir do
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Application.get_env(:microwaveprop, :canopy_tiles_dir, "/data/canopy")
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end
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end
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