From 8ae973c4cb4ebf4fd27ed65cbc3831098b790d2e Mon Sep 17 00:00:00 2001
From: Dan Paulat <dpaulat@gmail.com>
Date: Sat, 10 Feb 2024 00:08:13 -0600
Subject: [PATCH] Utility function to get geographic coordinate from i and j

---
 .../source/scwx/qt/util/geographic_lib.cpp    | 21 +++++++++++++++++++
 .../source/scwx/qt/util/geographic_lib.hpp    | 13 ++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/scwx-qt/source/scwx/qt/util/geographic_lib.cpp b/scwx-qt/source/scwx/qt/util/geographic_lib.cpp
index 8582d21c..20323eb8 100644
--- a/scwx-qt/source/scwx/qt/util/geographic_lib.cpp
+++ b/scwx-qt/source/scwx/qt/util/geographic_lib.cpp
@@ -1,6 +1,8 @@
 #include <scwx/qt/util/geographic_lib.hpp>
 #include <scwx/util/logger.hpp>
 
+#include <numbers>
+
 #include <GeographicLib/Gnomonic.hpp>
 #include <geos/algorithm/PointLocation.h>
 #include <geos/geom/CoordinateSequence.h>
@@ -90,6 +92,25 @@ GetAngle(double lat1, double lon1, double lat2, double lon2)
    return units::angle::degrees<double> {azi1};
 }
 
+common::Coordinate GetCoordinate(const common::Coordinate& center,
+                                 units::meters<double>     i,
+                                 units::meters<double>     j)
+{
+   // Calculate polar coordinates based on i and j
+   const double angle =
+      std::atan2(i.value(), j.value()) * 180.0 / std::numbers::pi;
+   const double range =
+      std::sqrt(i.value() * i.value() + j.value() * j.value());
+
+   double latitude;
+   double longitude;
+
+   DefaultGeodesic().Direct(
+      center.latitude_, center.longitude_, angle, range, latitude, longitude);
+
+   return {latitude, longitude};
+}
+
 units::length::meters<double>
 GetDistance(double lat1, double lon1, double lat2, double lon2)
 {
diff --git a/scwx-qt/source/scwx/qt/util/geographic_lib.hpp b/scwx-qt/source/scwx/qt/util/geographic_lib.hpp
index 66b4f42b..7f3f64bd 100644
--- a/scwx-qt/source/scwx/qt/util/geographic_lib.hpp
+++ b/scwx-qt/source/scwx/qt/util/geographic_lib.hpp
@@ -49,6 +49,19 @@ bool AreaContainsPoint(const std::vector<common::Coordinate>& area,
 units::angle::degrees<double>
 GetAngle(double lat1, double lon1, double lat2, double lon2);
 
+/**
+ * Get a coordinate from an (i, j) offset.
+ *
+ * @param [in] center The center coordinate from which i and j are offset
+ * @param [in] i The easting offset in meters
+ * @param [in] j The northing offset in meters
+ * 
+ * @return offset coordinate
+ */
+common::Coordinate GetCoordinate(const common::Coordinate& center,
+                                 units::meters<double>     i,
+                                 units::meters<double>     j);
+
 /**
  * Get the distance between two points.
  *