Graham McIntire
51e390959c
277 @spec/@type annotations added to 58 files covering all public APIs: contexts (propagation, radio, weather, terrain, beacons, commercial), GRIB2 decoders, terrain analysis, duct detection, rain scatter, CSV/ADIF import, weather clients, and all Ecto schemas. Dialyzer passes with 0 errors.
52 lines
1.8 KiB
Elixir
52 lines
1.8 KiB
Elixir
defmodule Microwaveprop.Geo do
|
|
@moduledoc "Geodetic helper functions: distances, bearings, coordinate math."
|
|
|
|
@earth_radius_km 6371.0
|
|
|
|
@doc "Great-circle distance between two points in km."
|
|
@spec haversine_km(number(), number(), number(), number()) :: float()
|
|
def haversine_km(lat1, lon1, lat2, lon2) do
|
|
dlat = deg_to_rad(lat2 - lat1)
|
|
dlon = deg_to_rad(lon2 - lon1)
|
|
|
|
a =
|
|
:math.sin(dlat / 2) ** 2 +
|
|
:math.cos(deg_to_rad(lat1)) * :math.cos(deg_to_rad(lat2)) * :math.sin(dlon / 2) ** 2
|
|
|
|
2 * @earth_radius_km * :math.asin(:math.sqrt(a))
|
|
end
|
|
|
|
@doc "Initial bearing from point 1 to point 2 in degrees (0-360)."
|
|
@spec bearing_deg(number(), number(), number(), number()) :: float()
|
|
def bearing_deg(lat1, lon1, lat2, lon2) do
|
|
lat1r = deg_to_rad(lat1)
|
|
lat2r = deg_to_rad(lat2)
|
|
dlonr = deg_to_rad(lon2 - lon1)
|
|
y = :math.sin(dlonr) * :math.cos(lat2r)
|
|
x = :math.cos(lat1r) * :math.sin(lat2r) - :math.sin(lat1r) * :math.cos(lat2r) * :math.cos(dlonr)
|
|
b = :math.atan2(y, x) * 180 / :math.pi()
|
|
Float.round(:math.fmod(b + 360, 360), 1)
|
|
end
|
|
|
|
@doc "Center of a 4-character Maidenhead grid square."
|
|
@spec maidenhead_center(String.t()) :: {float(), float()} | nil
|
|
def maidenhead_center(grid) when is_binary(grid) and byte_size(grid) >= 4 do
|
|
case Microwaveprop.Radio.Maidenhead.to_latlon(grid) do
|
|
{:ok, {lat, lon}} -> {lat, lon}
|
|
:error -> nil
|
|
end
|
|
end
|
|
|
|
@doc "4-character Maidenhead grid for a lat/lon."
|
|
@spec latlon_to_grid4(number(), number()) :: String.t()
|
|
def latlon_to_grid4(lat, lon) do
|
|
lon_field = trunc((lon + 180) / 20)
|
|
lat_field = trunc((lat + 90) / 10)
|
|
lon_sq = trunc(rem(trunc(lon + 180), 20) / 2)
|
|
lat_sq = trunc(rem(trunc(lat + 90), 10) / 1)
|
|
|
|
<<?A + lon_field, ?A + lat_field, ?0 + lon_sq, ?0 + lat_sq>>
|
|
end
|
|
|
|
defp deg_to_rad(d), do: d * :math.pi() / 180
|
|
end
|