From ae652cab3cf0541173b31273bcec5746a9a81e68 Mon Sep 17 00:00:00 2001
From: Rutger Broekhoff
Date: Fri, 11 Sep 2026 17:22:44 +0200
Subject: Speed improvements

---
 server/src/geo/utm.cppm | 44 +++++++++++++++++++++++++++-----------------
 1 file changed, 27 insertions(+), 17 deletions(-)

(limited to 'server/src/geo')

diff --git a/server/src/geo/utm.cppm b/server/src/geo/utm.cppm
index c58ffb4..75bba6f 100644
--- a/server/src/geo/utm.cppm
+++ b/server/src/geo/utm.cppm
@@ -110,6 +110,7 @@ using zonable_wgs84_linestring =
 // and easting (so no Norway/Svalbard exceptions).
 class zone
 {
+public:
   // Note: calculations heavily depend on the values of the variants.
   enum class hemisphere : std::uint8_t
   {
@@ -117,23 +118,6 @@ class zone
     southern = 1,
   };
 
-  // Negative if in the southern hemisphere
-  // Equal to (zone_no - 1) * 2 + hemisphere
-  // In range [0, 119]
-  std::uint8_t zone_;
-
-  static constexpr auto zone_no_valid(std::uint8_t zone_no) -> bool
-  {
-    return 0 < zone_no && zone_no <= 60;
-  }
-
-  static constexpr auto from(std::uint8_t zone_no, hemisphere h) -> std::uint8_t
-  {
-    if (!zone_no_valid(zone_no))
-      throw std::invalid_argument{"invalid UTM zone number"};
-    return (zone_no - 1) * 2 + static_cast<std::uint8_t>(h);
-  }
-
 public:
   explicit constexpr zone(std::uint8_t zone_no, hemisphere h)
     : zone_{from(zone_no, h)}
@@ -196,8 +180,34 @@ public:
   {
     return zone_ == rhs.zone_;
   }
+
+private:
+  static constexpr auto zone_no_valid(std::uint8_t zone_no) -> bool
+  {
+    return 0 < zone_no && zone_no <= 60;
+  }
+
+  static constexpr auto from(std::uint8_t zone_no, enum hemisphere h)
+      -> std::uint8_t
+  {
+    if (!zone_no_valid(zone_no))
+      throw std::invalid_argument{"invalid UTM zone number"};
+    return (zone_no - 1) * 2 + static_cast<std::uint8_t>(h);
+  }
+
+  // Negative if in the southern hemisphere
+  // Equal to (zone_no - 1) * 2 + hemisphere
+  // In range [0, 119]
+  std::uint8_t zone_;
 };
 static_assert(zone::min().as_index() == 0);
 static_assert(zone::max().as_index() == 119);
 
+auto to_string(zone z) -> std::string
+{
+  return std::format(
+      "{} {}", z.zone_no(),
+      z.hemisphere() == zone::hemisphere::northern ? "northern" : "southern");
+}
+
 } // namespace routemon::geo::utm
-- 
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