Graham McIntire
2defa3db7a
- Unify haversine_km / deg_to_rad: Geo is the canonical home (atan2
form for antipodal stability); Radio, common_volume, rain_scatter,
ionosphere, terrain/srtm, terrain/elevation_client now delegate.
- Drop safe_min/safe_max wrappers in favor of Enum.min/max defaults.
- Move parse_float / parse_int to MicrowavepropWeb.LiveHelpers; eme,
path, and rover LiveViews import from there.
- Extract MicrowavepropWeb.LocationResolver from the eme/path
resolve_source / resolve_location duplicate. Standardize the kind
key and "Invalid grid square" error message.
- Convert Scorer cond chains (humidity, td_depression, sky, wind,
rain, pwat, pressure) to multi-clause guarded defs, matching the
existing classify_time_period style.
- extract_profile_fields uses a named map accumulator instead of a
6-tuple; build_path_conditions guards on %{temps: []} / %{dewpoints: []}.
- Collapse scores_file clamp/3 to max |> min.
- humidity_effect_label lives in BandConfig; map_live and path_live
both use it.
59 lines
2.1 KiB
Elixir
59 lines
2.1 KiB
Elixir
defmodule Microwaveprop.Geo do
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@moduledoc "Geodetic helper functions: distances, bearings, coordinate math."
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alias Microwaveprop.Radio.Maidenhead
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@earth_radius_km 6371.0
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@doc "Great-circle distance between two points in km."
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@spec haversine_km(number(), number(), number(), number()) :: float()
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def haversine_km(lat1, lon1, lat2, lon2) do
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dlat = deg_to_rad(lat2 - lat1)
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dlon = deg_to_rad(lon2 - lon1)
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rlat1 = deg_to_rad(lat1)
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rlat2 = deg_to_rad(lat2)
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a =
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:math.sin(dlat / 2) ** 2 +
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:math.cos(rlat1) * :math.cos(rlat2) * :math.sin(dlon / 2) ** 2
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# `atan2(√a, √(1−a))` is the numerically stable form: when `a`
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# rounds to slightly above 1 the asin form returns NaN, while
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# atan2 stays finite.
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2 * @earth_radius_km * :math.atan2(:math.sqrt(a), :math.sqrt(1 - a))
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end
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@doc "Initial bearing from point 1 to point 2 in degrees (0-360)."
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@spec bearing_deg(number(), number(), number(), number()) :: float()
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def bearing_deg(lat1, lon1, lat2, lon2) do
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lat1r = deg_to_rad(lat1)
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lat2r = deg_to_rad(lat2)
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dlonr = deg_to_rad(lon2 - lon1)
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y = :math.sin(dlonr) * :math.cos(lat2r)
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x = :math.cos(lat1r) * :math.sin(lat2r) - :math.sin(lat1r) * :math.cos(lat2r) * :math.cos(dlonr)
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b = :math.atan2(y, x) * 180 / :math.pi()
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Float.round(:math.fmod(b + 360, 360), 1)
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end
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@doc "Center of a 4-character Maidenhead grid square."
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@spec maidenhead_center(String.t()) :: {float(), float()} | nil
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def maidenhead_center(grid) when is_binary(grid) and byte_size(grid) >= 4 do
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case Maidenhead.to_latlon(grid) do
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{:ok, {lat, lon}} -> {lat, lon}
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:error -> nil
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end
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end
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@doc "4-character Maidenhead grid for a lat/lon."
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@spec latlon_to_grid4(number(), number()) :: String.t()
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def latlon_to_grid4(lat, lon) do
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lon_field = trunc((lon + 180) / 20)
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lat_field = trunc((lat + 90) / 10)
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lon_sq = trunc(rem(trunc(lon + 180), 20) / 2)
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lat_sq = trunc(rem(trunc(lat + 90), 10) / 1)
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<<?A + lon_field, ?A + lat_field, ?0 + lon_sq, ?0 + lat_sq>>
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end
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defp deg_to_rad(d), do: d * :math.pi() / 180
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end
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