diff --git a/include/ui/radar_projection.h b/include/ui/radar_projection.h
new file mode 100644
index 000000000..4669a21f1
--- /dev/null
+++ b/include/ui/radar_projection.h
@@ -0,0 +1,20 @@
+#pragma once
+
+namespace ui::radar {
+
+constexpr float kKmPerDeg = 111.0f;
+constexpr float kDegToRad = 3.14159265f / 180.0f;
+
+/** Offset of lat/lon from the radar center, in km. */
+void offsetKmFromCenter(float lat, float lon, float* dx_km, float* dy_km,
+                        float* dist_km);
+
+/** Flat lat/lon as x/y: 1 deg ~ 111 km, north = screen up. */
+void latLonToScreen(float lat, float lon, int* out_x, int* out_y);
+
+int distSqFromCenter(int x, int y);
+
+/** Pull (x1,y1) back along the segment from (x0,y0) until inside the ring. */
+void clipPointToOuterRing(int x0, int y0, int* x1, int* y1);
+
+}  // namespace ui::radar
diff --git a/src/ui/radar_display.cpp b/src/ui/radar_display.cpp
index 3ececd6e8..2a61c9bb5 100644
--- a/src/ui/radar_display.cpp
+++ b/src/ui/radar_display.cpp
@@ -11,6 +11,7 @@
 #include "hardware/display_font.h"
 #include "services/adsb_client.h"
 #include "services/radar_location.h"
+#include "ui/radar_projection.h"
 #include "ui/radar_range.h"
 #include "ui/radar_theme.h"
 #include "ui/runway_overlay.h"
@@ -33,6 +34,11 @@ uint16_t kColorRunwayLabel = 0x7DFF;
 
 namespace {
 
+using radar::clipPointToOuterRing;
+using radar::distSqFromCenter;
+using radar::latLonToScreen;
+using radar::offsetKmFromCenter;
+
 bool s_label_metrics_ready = false;
 bool s_cardinal_use_vlw = false;
 bool s_scale_use_vlw = false;
@@ -197,22 +203,6 @@ void initPalette() {
                                           radar::kRunwayLabelB);
 }
 
-constexpr float kKmPerDeg = 111.0f;
-constexpr float kDegToRad = 3.14159265f / 180.0f;
-
-void offsetKmFromCenter(float lat, float lon, float* dx_km, float* dy_km,
-                        float* dist_km) {
-  // Longitude degrees shrink toward the poles; scale by cos(latitude) so
-  // east-west distance isn't overstated away from the equator.
-  const float center_lat_rad =
-      static_cast<float>(services::location::lat()) * kDegToRad;
-  *dx_km = static_cast<float>(lon - services::location::lon()) * kKmPerDeg *
-           cosf(center_lat_rad);
-  *dy_km =
-      static_cast<float>(lat - services::location::lat()) * kKmPerDeg;
-  *dist_km = sqrtf((*dx_km) * (*dx_km) + (*dy_km) * (*dy_km));
-}
-
 float innerRingMaxKm() {
   const float outer_km = radar::rangeCurrent().outer_km;
   return outer_km * (static_cast<float>(radar::kGridOuterRadius -
@@ -220,28 +210,8 @@ float innerRingMaxKm() {
                      static_cast<float>(radar::kGridOuterRadius));
 }
 
-/** Flat lat/lon as x/y: 1° ≈ 111 km, north = screen up. */
-void latLonToScreen(float lat, float lon, int* out_x, int* out_y) {
-  const float outer_km = radar::rangeCurrent().outer_km;
-  const float px_per_km = static_cast<float>(radar::kGridOuterRadius) / outer_km;
-
-  float dx_km = 0.0f;
-  float dy_km = 0.0f;
-  float dist_km = 0.0f;
-  offsetKmFromCenter(lat, lon, &dx_km, &dy_km, &dist_km);
-
-  *out_x = radar::kCenterX + static_cast<int>(lroundf(dx_km * px_per_km));
-  *out_y = radar::kCenterY - static_cast<int>(lroundf(dy_km * px_per_km));
-}
-
 bool isInsideOuterRingKm(float dist_km) { return dist_km <= innerRingMaxKm(); }
 
-int distSqFromCenter(int x, int y) {
-  const int dx = x - radar::kCenterX;
-  const int dy = y - radar::kCenterY;
-  return dx * dx + dy * dy;
-}
-
 bool isInsideOuterRing(int x, int y) {
   const int max_r = radar::kGridOuterRadius - radar::kAircraftInsideRingInsetPx;
   return distSqFromCenter(x, y) <= max_r * max_r;
@@ -275,33 +245,6 @@ void drawBeyondRingDot(int x, int y) {
                            radar::kColorAircraft);
 }
 
-void clipPointToOuterRing(int x0, int y0, int* x1, int* y1) {
-  const int max_r = radar::kGridOuterRadius;
-  const int max_r_sq = max_r * max_r;
-  if (distSqFromCenter(*x1, *y1) <= max_r_sq) {
-    return;
-  }
-
-  const int dx = *x1 - x0;
-  const int dy = *y1 - y0;
-  float t = 1.0f;
-  for (int step = 0; step < 20; ++step) {
-    const int px = x0 + static_cast<int>(lroundf(dx * t));
-    const int py = y0 + static_cast<int>(lroundf(dy * t));
-    if (distSqFromCenter(px, py) <= max_r_sq) {
-      *x1 = px;
-      *y1 = py;
-      return;
-    }
-    t -= 0.05f;
-    if (t <= 0.0f) {
-      *x1 = x0;
-      *y1 = y0;
-      return;
-    }
-  }
-}
-
 int speedLineLengthPx(float gs_knots) {
   if (gs_knots <= 0.0f) {
     return 0;
diff --git a/src/ui/radar_projection.cpp b/src/ui/radar_projection.cpp
new file mode 100644
index 000000000..33230abc8
--- /dev/null
+++ b/src/ui/radar_projection.cpp
@@ -0,0 +1,69 @@
+#include "ui/radar_projection.h"
+
+#include <cmath>
+
+#include "services/radar_location.h"
+#include "ui/radar_range.h"
+#include "ui/radar_theme.h"
+
+namespace ui::radar {
+
+void offsetKmFromCenter(float lat, float lon, float* dx_km, float* dy_km,
+                        float* dist_km) {
+  // Longitude degrees shrink toward the poles; scale by cos(latitude) so
+  // east-west distance isn't overstated away from the equator.
+  const float center_lat_rad =
+      static_cast<float>(services::location::lat()) * kDegToRad;
+  *dx_km = static_cast<float>(lon - services::location::lon()) * kKmPerDeg *
+           cosf(center_lat_rad);
+  *dy_km = static_cast<float>(lat - services::location::lat()) * kKmPerDeg;
+  *dist_km = sqrtf((*dx_km) * (*dx_km) + (*dy_km) * (*dy_km));
+}
+
+void latLonToScreen(float lat, float lon, int* out_x, int* out_y) {
+  const float outer_km = rangeCurrent().outer_km;
+  const float px_per_km = static_cast<float>(kGridOuterRadius) / outer_km;
+
+  float dx_km = 0.0f;
+  float dy_km = 0.0f;
+  float dist_km = 0.0f;
+  offsetKmFromCenter(lat, lon, &dx_km, &dy_km, &dist_km);
+
+  *out_x = kCenterX + static_cast<int>(lroundf(dx_km * px_per_km));
+  *out_y = kCenterY - static_cast<int>(lroundf(dy_km * px_per_km));
+}
+
+int distSqFromCenter(int x, int y) {
+  const int dx = x - kCenterX;
+  const int dy = y - kCenterY;
+  return dx * dx + dy * dy;
+}
+
+void clipPointToOuterRing(int x0, int y0, int* x1, int* y1) {
+  const int max_r = kGridOuterRadius;
+  const int max_r_sq = max_r * max_r;
+  if (distSqFromCenter(*x1, *y1) <= max_r_sq) {
+    return;
+  }
+
+  const int dx = *x1 - x0;
+  const int dy = *y1 - y0;
+  float t = 1.0f;
+  for (int step = 0; step < 20; ++step) {
+    const int px = x0 + static_cast<int>(lroundf(dx * t));
+    const int py = y0 + static_cast<int>(lroundf(dy * t));
+    if (distSqFromCenter(px, py) <= max_r_sq) {
+      *x1 = px;
+      *y1 = py;
+      return;
+    }
+    t -= 0.05f;
+    if (t <= 0.0f) {
+      *x1 = x0;
+      *y1 = y0;
+      return;
+    }
+  }
+}
+
+}  // namespace ui::radar
diff --git a/src/ui/runway_overlay.cpp b/src/ui/runway_overlay.cpp
index d32828551..41ed50928 100644
--- a/src/ui/runway_overlay.cpp
+++ b/src/ui/runway_overlay.cpp
@@ -8,14 +8,18 @@
 #include "data/large_airports.h"
 #include "hardware/display_font.h"
 #include "services/radar_location.h"
+#include "ui/radar_projection.h"
 #include "ui/radar_range.h"
 #include "ui/radar_theme.h"
 
 namespace ui::runway {
 namespace {
 
-constexpr float kKmPerDeg = 111.0f;
-constexpr float kDegToRad = 3.14159265f / 180.0f;
+using radar::clipPointToOuterRing;
+using radar::distSqFromCenter;
+using radar::latLonToScreen;
+using radar::offsetKmFromCenter;
+
 constexpr size_t kMaxAirportLabels = 32;
 
 bool s_in_range[data::large_airports::kAirportCount];
@@ -71,66 +75,6 @@ void applyRunwayLabelStyle(lgfx::LGFXBase& gfx) {
 
 float e7ToDeg(int32_t e7) { return static_cast<float>(e7) * 1e-7f; }
 
-void offsetKmFromCenter(float lat, float lon, float* dx_km, float* dy_km,
-                        float* dist_km) {
-  // Longitude degrees shrink toward the poles; scale by cos(latitude) so
-  // east-west distance isn't overstated away from the equator.
-  const float center_lat_rad =
-      static_cast<float>(services::location::lat()) * kDegToRad;
-  *dx_km = static_cast<float>(lon - services::location::lon()) * kKmPerDeg *
-           cosf(center_lat_rad);
-  *dy_km =
-      static_cast<float>(lat - services::location::lat()) * kKmPerDeg;
-  *dist_km = sqrtf((*dx_km) * (*dx_km) + (*dy_km) * (*dy_km));
-}
-
-void latLonToScreen(float lat, float lon, int* out_x, int* out_y) {
-  const float outer_km = radar::rangeCurrent().outer_km;
-  const float px_per_km =
-      static_cast<float>(radar::kGridOuterRadius) / outer_km;
-
-  float dx_km = 0.0f;
-  float dy_km = 0.0f;
-  float dist_km = 0.0f;
-  offsetKmFromCenter(lat, lon, &dx_km, &dy_km, &dist_km);
-
-  *out_x = radar::kCenterX + static_cast<int>(lroundf(dx_km * px_per_km));
-  *out_y = radar::kCenterY - static_cast<int>(lroundf(dy_km * px_per_km));
-}
-
-int distSqFromCenter(int x, int y) {
-  const int dx = x - radar::kCenterX;
-  const int dy = y - radar::kCenterY;
-  return dx * dx + dy * dy;
-}
-
-void clipPointToOuterRing(int x0, int y0, int* x1, int* y1) {
-  const int max_r = radar::kGridOuterRadius;
-  const int max_r_sq = max_r * max_r;
-  if (distSqFromCenter(*x1, *y1) <= max_r_sq) {
-    return;
-  }
-
-  const int dx = *x1 - x0;
-  const int dy = *y1 - y0;
-  float t = 1.0f;
-  for (int step = 0; step < 20; ++step) {
-    const int px = x0 + static_cast<int>(lroundf(dx * t));
-    const int py = y0 + static_cast<int>(lroundf(dy * t));
-    if (distSqFromCenter(px, py) <= max_r_sq) {
-      *x1 = px;
-      *y1 = py;
-      return;
-    }
-    t -= 0.05f;
-    if (t <= 0.0f) {
-      *x1 = x0;
-      *y1 = y0;
-      return;
-    }
-  }
-}
-
 bool segmentIntersectsDisc(int x0, int y0, int x1, int y1) {
   const int cx = radar::kCenterX;
   const int cy = radar::kCenterY;