diff --git a/radio/src/maths.cpp b/radio/src/maths.cpp
index 01d228cb1..f1244b1af 100644
--- a/radio/src/maths.cpp
+++ b/radio/src/maths.cpp
@@ -128,6 +128,7 @@ uint16_t isqrt32(uint32_t n)
 */
 
 #if defined(FRSKY_HUB) && !defined(CPUARM)
+// convert latitude and longitude to 1/10^6 degrees
 void extractLatitudeLongitude(uint32_t * latitude, uint32_t * longitude)
 {
   div_t qr = div(telemetryData.hub.gpsLatitude_bp, 100);
@@ -140,10 +141,12 @@ void extractLatitudeLongitude(uint32_t * latitude, uint32_t * longitude)
 void getGpsPilotPosition()
 {
   extractLatitudeLongitude(&telemetryData.hub.pilotLatitude, &telemetryData.hub.pilotLongitude);
+  // distFromEarthAxis = cos(lat) * EARTH_RADIUS
+  // 1 - x2/2 + x4/24
   uint32_t lat = telemetryData.hub.pilotLatitude / 10000;
   uint32_t angle2 = (lat*lat) / 10000;
   uint32_t angle4 = angle2 * angle2;
-  telemetryData.hub.distFromEarthAxis = 139*(((uint32_t)10000000-((angle2*(uint32_t)123370)/81)+(angle4/25))/12500);
+  telemetryData.hub.distFromEarthAxis = 139 * (((uint32_t)10000000-((angle2*(uint32_t)123370)/81)+(angle4/25)) / 12500);
   // TRACE("telemetryData.hub.distFromEarthAxis=%d", telemetryData.hub.distFromEarthAxis);
 }
 
diff --git a/radio/src/opentx.h b/radio/src/opentx.h
index 89e099521..7357971f0 100644
--- a/radio/src/opentx.h
+++ b/radio/src/opentx.h
@@ -1557,7 +1557,7 @@ extern uint8_t s_frsky_view;
 #endif
 
 #define EARTH_RADIUSKM ((uint32_t)6371)
-#define EARTH_RADIUS ((uint32_t)111194)
+#define EARTH_RADIUS ((uint32_t)111194) // meters * pi / 180°
 
 void getGpsPilotPosition();
 void getGpsDistance();