From d3ae404f7a37feed07f140c23130eea5738c1d94 Mon Sep 17 00:00:00 2001
From: Dan Paulat <dpaulat@gmail.com>
Date: Mon, 2 Dec 2024 22:38:12 -0600
Subject: [PATCH] Delta angles must be normalized before they can be scaled

---
 .../scwx/qt/view/level2_product_view.cpp      | 31 +++++++++++++++----
 1 file changed, 25 insertions(+), 6 deletions(-)

diff --git a/scwx-qt/source/scwx/qt/view/level2_product_view.cpp b/scwx-qt/source/scwx/qt/view/level2_product_view.cpp
index 0254904b..c483ab28 100644
--- a/scwx-qt/source/scwx/qt/view/level2_product_view.cpp
+++ b/scwx-qt/source/scwx/qt/view/level2_product_view.cpp
@@ -116,6 +116,7 @@ public:
 
    static bool IsRadarDataIncomplete(
       const std::shared_ptr<const wsr88d::rda::ElevationScan>& radarData);
+   static units::degrees<float> NormalizeAngle(units::degrees<float> angle);
 
    Level2ProductView* self_;
 
@@ -1042,10 +1043,9 @@ void Level2ProductView::Impl::ComputeCoordinates(
                const units::degrees<float> prevAngle =
                   prevRadial1->second->azimuth_angle();
 
-               // No wrapping required since angle is only used for geodesic
-               // calculation
+               // Calculate delta angle
                const units::degrees<float> deltaAngle =
-                  currentAngle - prevAngle;
+                  NormalizeAngle(currentAngle - prevAngle);
 
                // Delta scale is half the delta angle to reach the center of the
                // bin, because smoothing is enabled
@@ -1076,9 +1076,9 @@ void Level2ProductView::Impl::ComputeCoordinates(
                const units::degrees<float> prevAngle2 =
                   prevRadial2->second->azimuth_angle();
 
-               // No wrapping required since angle is only used for geodesic
-               // calculation
-               const units::degrees<float> deltaAngle = prevAngle1 - prevAngle2;
+               // Calculate delta angle
+               const units::degrees<float> deltaAngle =
+                  NormalizeAngle(prevAngle1 - prevAngle2);
 
                const float deltaScale =
                   (smoothingEnabled) ?
@@ -1162,6 +1162,25 @@ bool Level2ProductView::Impl::IsRadarDataIncomplete(
    return angleDelta > kIncompleteDataAngleThreshold_;
 }
 
+units::degrees<float>
+Level2ProductView::Impl::NormalizeAngle(units::degrees<float> angle)
+{
+   constexpr auto angleLimit = units::degrees<float> {180.0f};
+   constexpr auto fullAngle  = units::degrees<float> {360.0f};
+
+   // Normalize angle to [-180, 180)
+   while (angle < -angleLimit)
+   {
+      angle += fullAngle;
+   }
+   while (angle >= angleLimit)
+   {
+      angle -= fullAngle;
+   }
+
+   return angle;
+}
+
 std::optional<std::uint16_t>
 Level2ProductView::GetBinLevel(const common::Coordinate& coordinate) const
 {