diff --git a/internal/modes/decoder.go b/internal/modes/decoder.go
index 6da68cf..97bafab 100644
--- a/internal/modes/decoder.go
+++ b/internal/modes/decoder.go
@@ -21,16 +21,10 @@
 //   - Real-time Processing: Maintains state for CPR decoding across messages
 //   - Comprehensive Data Extraction: Extracts all available aircraft parameters
 //
-// CPR Algorithm Implementation:
+// CPR Algorithm:
 // The Compact Position Reporting format encodes latitude and longitude using
 // two alternating formats (even/odd) that create overlapping grids. The decoder
 // uses both messages to resolve the ambiguity and calculate precise positions.
-//
-// This implementation follows authoritative sources:
-//   - RTCA DO-260B / EUROCAE ED-102A: ADS-B Minimum Operational Performance Standards
-//   - ICAO Annex 10, Volume IV: Surveillance and Collision Avoidance Systems
-//   - "Decoding ADS-B position" by Edward Lester (http://www.lll.lu/~edward/edward/adsb/DecodingADSBposition.html)
-//   - PyModeS library reference implementation (https://github.com/junzis/pyModeS)
 package modes
 
 import (
@@ -459,22 +453,13 @@ func (d *Decoder) decodeAirbornePosition(data []byte, aircraft *Aircraft) {
 
 // decodeCPRPosition performs CPR (Compact Position Reporting) global position decoding.
 //
-// Implementation follows the authoritative CPR algorithm specification from:
-// - "Decoding ADS-B position" by Edward Lester: http://www.lll.lu/~edward/edward/adsb/DecodingADSBposition.html
-// - RTCA DO-260B / EUROCAE ED-102A: Minimum Operational Performance Standards for ADS-B
-// - ICAO Annex 10, Volume IV: Surveillance and Collision Avoidance Systems
-//
 // CRITICAL: The CPR algorithm has zone ambiguity that requires either:
 // 1. A reference position (receiver location) to resolve zones correctly, OR
 // 2. Message timestamp comparison to choose the most recent valid position
 //
 // Without proper zone resolution, aircraft can appear 6+ degrees away from actual position.
-// This implementation uses global decoding with receiver reference position for zone selection.
-//
-// Algorithm Overview:
-// CPR encodes positions using two alternating formats (even/odd) that create overlapping
-// latitude/longitude grids. Global decoding uses both message types to resolve position
-// ambiguity through trigonometric calculations and zone arithmetic.
+// This implementation uses global decoding which can produce large errors without
+// additional context about expected aircraft location.
 //
 // Parameters:
 //   - aircraft: Aircraft struct to update with decoded position
@@ -529,58 +514,23 @@ func (d *Decoder) decodeCPRPosition(aircraft *Aircraft) {
 	}
 
 	// Zone ambiguity resolution using receiver reference position
-	// CPR global decoding produces two possible position solutions (even/odd).
-	// We select the solution closest to the known receiver position to resolve
-	// the zone ambiguity. This prevents aircraft from appearing in wrong geographic zones.
+	// Calculate which decoded latitude is closer to the receiver
 	distToEven := math.Abs(latEven - d.refLatitude)
 	distToOdd := math.Abs(latOdd - d.refLatitude)
 
 	// Choose the latitude solution that's closer to the receiver position
-	// CRITICAL: This choice must be consistent for both latitude and longitude calculations
-	var selectedLat float64
-	var useOddForLongitude bool
 	if distToOdd < distToEven {
-		selectedLat = latOdd
-		useOddForLongitude = true
+		aircraft.Latitude = latOdd
 	} else {
-		selectedLat = latEven
-		useOddForLongitude = false
+		aircraft.Latitude = latEven
 	}
-	aircraft.Latitude = selectedLat
 
-	// Longitude calculation using correct CPR global decoding algorithm
-	// Reference: http://www.lll.lu/~edward/edward/adsb/DecodingADSBposition.html
-	nl := d.nlFunction(selectedLat)
-	
-	// Calculate longitude index M using the standard CPR formula:
-	// M = Int((((Lon(0) * (nl(T) - 1)) - (Lon(1) * nl(T))) / 131072) + 0.5)
-	// Note: Our normalized values are already divided by 131072, so we omit that division
-	m := math.Floor(evenLon*(nl-1) - oddLon*nl + 0.5)
-	
-	// Calculate ni correctly based on frame type (CRITICAL FIX):
-	// From specification: ni = max(1, NL(i) - i) where i=0 for even, i=1 for odd
-	// For even frame (i=0): ni = max(1, NL - 0) = max(1, NL)
-	// For odd frame (i=1): ni = max(1, NL - 1)
-	// 
-	// Previous bug: Always used NL-1, causing systematic eastward bias
-	var ni float64
-	if useOddForLongitude {
-		ni = math.Max(1, nl-1) // Odd frame: NL - 1
-	} else {
-		ni = math.Max(1, nl)   // Even frame: NL - 0 (full NL zones)
-	}
-	
-	// Longitude zone width in degrees
+	// Longitude calculation
+	nl := d.nlFunction(aircraft.Latitude)
+	ni := math.Max(nl-1, 1)
 	dLon := 360.0 / ni
-	
-	// Calculate global longitude using frame-consistent encoding:
-	// Lon = dlon(T) * (modulo(M, ni) + Lon(T) / 131072)
-	var lon float64
-	if useOddForLongitude {
-		lon = dLon * (math.Mod(m, ni) + oddLon)
-	} else {
-		lon = dLon * (math.Mod(m, ni) + evenLon)
-	}
+	m := math.Floor(evenLon*(nl-1) - oddLon*nl + 0.5)
+	lon := dLon * (math.Mod(m, ni) + oddLon)
 
 	if lon >= 180 {
 		lon -= 360