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Vectorize loxodrome_inverse() #1881

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joa-quim merged 1 commit into from
Jan 20, 2026
Merged

Vectorize loxodrome_inverse() #1881

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16 changes: 8 additions & 8 deletions src/loxodromics.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -32,11 +32,11 @@ function loxodrome_inverse(lon1, lat1, lon2, lat2, a=6378137.0, f=0.003352810664
isolat2 = isometric_lat(lat2, e2)

# Compute changes in isometric latitude and longitude between P1 and P2
Az12 = atan((lon2 - lon1), (isolat2 - isolat1)) # The azimuth
Az12 = atan.((lon2 .- lon1), (isolat2 .- isolat1)) # The azimuth
# Compute distance along loxodromic curve
m1 = meridian_dist(lat1, a, e2)
m2 = meridian_dist(lat2, a, e2)
lox_s = (m2 - m1) / cos(Az12);
lox_s = (m2 .- m1) ./ cos.(Az12);

@ZMAlt ZMAlt Jan 20, 2026

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Suggested change
lox_s = (m2 .- m1) ./ cos.(Az12);
lox_s = @. (m2 - m1) / cos(Az12);

Hi, Joa, you can simplify the code like this

@joa-quim joa-quim Jan 20, 2026

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Yes, I know, thanks, but I guess I prefer avoid using macros when I can..

return lox_s, Az12 / D2R
end

Expand Down Expand Up @@ -99,11 +99,11 @@ function loxodrome_direct(lon, lat, azim, dist, a=6378137.0, f=0.003352810664747
end

function f_phi(lat, A0, A2, A4, A6, A8, A10)
A0*lat - (A2/2)*sin(2*lat) + (A4/4)*sin(4*lat) - (A6/6)*sin(6*lat) + (A8/8)*sin(8*lat) - (A10/10)*sin(10*lat)
A0*lat .- (A2/2)*sin.(2*lat) .+ (A4/4)*sin.(4*lat) .- (A6/6)*sin.(6*lat) .+ (A8/8)*sin.(8*lat) .- (A10/10)*sin.(10*lat)
end

function f_prime_phi(lat, A0, A2, A4, A6, A8, A10)
A0 - A2 * cos(2*lat) + A4 * cos(4*lat) - A6 * cos(6*lat) + A8 * cos(8*lat) - A10 * cos(10*lat)
A0 .- A2 * cos.(2*lat) .+ A4 * cos.(4*lat) .- A6 * cos.(6*lat) .+ A8 * cos.(8*lat) .- A10 * cos.(10*lat)
end

function meridian_dist(lat, a, e2)
Expand All @@ -129,8 +129,8 @@ end
function isometric_lat(lat, ecc2)
# Compute isometric latitude. ECC2 is the squared eccentricity = f*(2-f), where f is the flattening
ecc = sqrt(ecc2)
x = ecc * sin(lat)
y = (1-x) / (1+x)
z = pi/4 + lat/2
log(tan(z) * (y^(ecc/2)))
x = ecc .* sin.(lat)
y = (1 .- x) ./ (1 .+ x)
z = pi/4 .+ lat/2
log.(tan.(z) .* (y.^(ecc/2)))
end
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