Fix converting GPS longitude unint

sohstationviewer/view/plotting/gps_dialog.py

@@ -49,9 +49,12 @@ class GPSWidget(QtWidgets.QWidget):
 
         latitude_range = max_latitude - min_latitude
         longitude_range = max_longitude - min_longitude
-        longitude_range = convert_longitude_degree_to_meter(longitude_range,
-                                                            latitude_range)
         latitude_range = convert_latitude_degree_to_meter(latitude_range)
+        # Use the average latitude as the latitude in the longitude conversion
+        # to find the average range of longitude.
+        longitude_range = convert_longitude_degree_to_meter(
+            longitude_range, (max_latitude + min_latitude) / 2
+        )
 
         self.ax.plot(all_longitudes, all_latitudes, 'ws', markersize=4,
                      markeredgecolor='black', picker=True, pickradius=4)
@@ -219,7 +222,7 @@ def convert_longitude_degree_to_meter(long: float, lat: float) -> float:
     long_degree_length_in_meter = EQUATORIAL_CIRCUMFERENCE / 360
     # The length of a longitude degree varies with the latitude, being greatest
     # around the equator and approaching 0 near to the poles.
-    adjustment_for_latitude = math.cos(lat)
+    adjustment_for_latitude = math.cos(math.radians(lat))
     return long * long_degree_length_in_meter * adjustment_for_latitude