From 3cbeb243ef957d1418a6b25624a26c09433cd729 Mon Sep 17 00:00:00 2001
From: Jay Kickliter <jay@kickliter.com>
Date: Wed, 18 Oct 2023 12:12:56 -0600
Subject: [PATCH] [terrain] propperly take supplied earth radius into account

---
 propah/src/p2p.rs      | 1 +
 terrain/src/math.rs    | 5 ++---
 terrain/src/profile.rs | 5 +++--
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/propah/src/p2p.rs b/propah/src/p2p.rs
index d67675d..533c4d3 100644
--- a/propah/src/p2p.rs
+++ b/propah/src/p2p.rs
@@ -198,6 +198,7 @@ where
             .end_alt(self.end_alt_m)
             .earth_curve(self.earth_curve)
             .normalize(self.normalize)
+            .earth_radius(self.earth_radius)
             .build(tiles)?;
 
         // Unwrap is fine as profiles always have at least two points.
diff --git a/terrain/src/math.rs b/terrain/src/math.rs
index 798a028..d68d213 100644
--- a/terrain/src/math.rs
+++ b/terrain/src/math.rs
@@ -148,11 +148,10 @@ where
 }
 
 /// Returns the up/down angle (in radians) from a to b.
-pub fn elevation_angle<T>(start_elev_m: T, distance_m: T, end_elev_m: T) -> T
+pub fn elevation_angle<T>(start_elev_m: T, distance_m: T, end_elev_m: T, earth_radius: T) -> T
 where
     T: Float + FloatConst,
 {
-    let earth_radius = T::from(MEAN_EARTH_RADIUS).unwrap();
     let a = distance_m;
     let b = start_elev_m + earth_radius;
     let c = end_elev_m + earth_radius;
@@ -211,7 +210,7 @@ mod tests {
     fn test_elevation_angle() {
         assert_relative_eq!(
             0.100_167_342_359_641_42,
-            elevation_angle(1.0, 1.0, 1.1),
+            elevation_angle(1.0, 1.0, 1.1, super::MEAN_EARTH_RADIUS),
             epsilon = f64::EPSILON
         );
     }
diff --git a/terrain/src/profile.rs b/terrain/src/profile.rs
index 1adb360..2793437 100644
--- a/terrain/src/profile.rs
+++ b/terrain/src/profile.rs
@@ -189,13 +189,14 @@ where
             let now = std::time::Instant::now();
             if self.earth_curve {
                 // https://www.trailnotes.org/SizeOfTheEarth/
-                let earth_radius = C::from(crate::constants::MEAN_EARTH_RADIUS).unwrap();
+                let earth_radius = self.earth_radius;
                 let start_elev_alt =
                     *terrain_elev_m.first().unwrap() + C::from(self.start_alt_m).unwrap();
                 let start_radius_m = earth_radius + start_elev_alt;
                 let end_elev_alt =
                     *terrain_elev_m.last().unwrap() + C::from(self.end_alt_m).unwrap();
-                let elev_angle_rad = elevation_angle(start_elev_alt, distance_m, end_elev_alt);
+                let elev_angle_rad =
+                    elevation_angle(start_elev_alt, distance_m, end_elev_alt, self.earth_radius);
 
                 let (nb, nm) = if self.normalize {
                     let nb = -start_elev_alt;