up

internal/dxcc/dxcc.go

@@ -209,7 +209,13 @@ func parseEntityHeader(line string) *Entity {
 	e.CQZone, _ = strconv.Atoi(strings.TrimSpace(parts[1]))
 	e.ITUZone, _ = strconv.Atoi(strings.TrimSpace(parts[2]))
 	e.Lat, _ = strconv.ParseFloat(strings.TrimSpace(parts[4]), 64)
-	e.Lon, _ = strconv.ParseFloat(strings.TrimSpace(parts[5]), 64)
+	// cty.dat longitude is "+ for West" (e.g. France 2°E = -2.00, USA 92°W =
+	// +91.87). Negate it to the standard "+ for East" the rest of the app uses
+	// (grids, bearing/distance math), otherwise every cty.dat-derived azimuth and
+	// cluster distance is mirrored east↔west.
+	if lon, err := strconv.ParseFloat(strings.TrimSpace(parts[5]), 64); err == nil {
+		e.Lon = -lon
+	}
 	e.TZOffset, _ = strconv.ParseFloat(strings.TrimSpace(parts[6]), 64)
 	if e.Name == "" {
 		return nil
@@ -241,7 +247,8 @@ func parsePrefix(s string, e *Entity) (prefixEntry, bool) {
 			lat, e1 := strconv.ParseFloat(a, 64)
 			lon, e2 := strconv.ParseFloat(b, 64)
 			if e1 == nil && e2 == nil {
-				out.latOverride, out.lonOverride = lat, lon
+				// Same "+ for West" → "+ for East" flip as the entity header.
+				out.latOverride, out.lonOverride = lat, -lon
 				out.hasLatLon = true
 			}
 		}

internal/dxcc/dxcc_test.go

@@ -17,6 +17,22 @@ United States:            05:  08:  NA:   37.53:    91.67:     5.0:  K:
     =W1AW(5)[7],K,N,W,AA,AB,AC,AD,AE,AF,AG,AH,AI,AJ,AK;
 `
 
+// cty.dat stores longitude "+ for West"; we normalise to the standard
+// "+ for East" so bearing/distance math (and the cluster map) aren't mirrored.
+// Regression guard for the Svalbard-azimuth bug (356° instead of 4°).
+func TestLongitudeSign(t *testing.T) {
+	db, err := Load(strings.NewReader(sampleCty))
+	if err != nil {
+		t.Fatalf("load: %v", err)
+	}
+	if m, ok := db.Lookup("F4BPO"); !ok || m.Lon <= 0 { // France 2°E → +2
+		t.Errorf("France lon = %v, want positive (East)", m.Lon)
+	}
+	if m, ok := db.Lookup("K1ABC"); !ok || m.Lon >= 0 { // USA 92°W → ~-91.67
+		t.Errorf("USA lon = %v, want negative (West)", m.Lon)
+	}
+}
+
 func TestLookup(t *testing.T) {
 	db, err := Load(strings.NewReader(sampleCty))
 	if err != nil {