imported>Legoktm: Replace Module:No globals with require( "strict" )

2022-10-23T21:01:45Z

Replace Module:No globals with require( "strict" )

New page

--[[--------------------------< B E A R I N G >----------------------------------------------------------------

calculates the bearing from <from_lat>/<from_long> to <to_lat>/<to_long> using the equation from
https://www.igismap.com/formula-to-find-bearing-or-heading-angle-between-two-points-latitude-longitude/

written as a response to [ [User_talk:Trappist_the_monk#Hello,_bearings] ]

inputs in decimal degrees (degrees minutes seconds coordinates must be pre-converted)
<from_lat> – latitude (north +, south -) of the starting point
<from_long> – longitude (east +, west -) of the starting point
<to_lat> – latitude (north +, south -) of the ending point
<to_long> – longitude (east +, west -) of the ending point

returns bearing from 'from' to 'to' in decimal degrees

This code only works from the debug console:
=p.bearing (39.099912, -94.581213, 38.627089, -90.200203) -- original worked example St Louis, Missouri bears 96.5° from Kansas City, Kansas
=p.bearing (38.627089, -90.200203, 39.099912, -94.581213) -- reversed example: Kansas City, Kansas bears 279.3° from St Louis, Missouri

for negative lat/long (south/west) do not use U+2212 minus sign; use keyboard U+002D hyphen-minus

]]

require ('strict');

local function bearing (from_lat, from_long, to_lat, to_long)
local from_lat_rad = math.rad (from_lat); -- convert degree inputs to radians
local from_long_rad = math.rad (from_long);
local to_lat_rad = math.rad (to_lat);
local to_long_rad = math.rad (to_long);

local delta_long_rad = to_long_rad - from_long_rad;
local x = math.cos (to_lat_rad) * math.sin (delta_long_rad);
local y = (math.cos (from_lat_rad) * math.sin (to_lat_rad)) - (math.sin (from_lat_rad) * math.cos (to_lat_rad) * math.cos (delta_long_rad));
local beta = math.atan2 (x, y); -- result in radians
beta = math.deg (beta); -- convert to degrees
return (0.0 > beta) and (beta + 360.0) or beta; -- when beta is negative, add 360 degrees to make a positive bearing
end

--[[--------------------------< E X P O R T S >----------------------------------------------------------------
]]

return {
bearing = bearing,
}

Module:Sandbox/trappist the monk/bearing - Revision history

imported>Legoktm: Replace Module:No globals with require( "strict" )