Added a new Maidenhead class for plotting grid squares on the world map. Work in progress. Addresses issue #59.

pyqso/world_map.py

@@ -19,6 +19,7 @@
 
 from gi.repository import GObject
 import logging
+import re
 from os.path import expanduser
 from datetime import datetime
 try:
@@ -33,6 +34,7 @@ try:
     import cartopy
     logging.info("Using version %s of cartopy." % (cartopy.__version__))
     from matplotlib.backends.backend_gtk3cairo import FigureCanvasGTK3Cairo as FigureCanvas
+    from matplotlib.backends.backend_gtk3 import NavigationToolbar2GTK3
     have_necessary_modules = True
 except ImportError as e:
     logging.warning(e)
@@ -46,6 +48,10 @@ except ImportError:
     have_geocoder = False
 
 
+class NavigationToolbar(NavigationToolbar2GTK3):
+    toolitems = [t for t in NavigationToolbar2GTK3.toolitems if t[0] in ("Home", "Zoom", "Save")]
+
+
 class Point:
     """ A point on the grey line map. """
     def __init__(self, name, latitude, longitude, style="yo"):
@@ -64,6 +70,66 @@ class Point:
         return
 
 
+class Maidenhead:
+
+    """ The Maidenhead Locator System. """
+
+    def __init__(self):
+        self.upper = "ABCDEFGHIJKLMNOPQR"
+        self.lower = "abcdefghijklmnopqrstuvwx"
+        return
+
+    def ll2gs(self, latitude, longitude):
+        """ Convert latitude-longitude coordinates to a Maidenhead grid square locator.
+        This is based on the code by Walter Underwood, K6WRU (https://ham.stackexchange.com/questions/221/how-can-one-convert-from-lat-long-to-grid-square).
+
+        :arg float latitude: The latitude.
+        :arg float longitude: The longitude.
+        :rtype: str
+        :returns: The Maidenhead grid square locator.
+        """
+
+        adjusted_latitude = latitude + 90
+        adjusted_longitude = longitude + 180
+        field_latitude = self.upper[int(adjusted_latitude/10)]
+        field_longitude = self.upper[int(adjusted_longitude/20)]
+        square_latitude = int(adjusted_latitude % 10)
+        square_longitude = int((adjusted_longitude/2) % 10)
+
+        return ("%s"*4) % (field_longitude, field_latitude, square_longitude, square_latitude)
+
+    def gs2ll(self, grid_square):
+        """ Convert a Maidenhead grid square locator to latitude-longitude coordinates.
+        This is based on the gridSquareToLatLon function in HamGridSquare.js by Paul Brewer, KI6CQ (https://gist.github.com/DrPaulBrewer/4279e9d234a1bd6dd3c0), released under the MIT license.
+
+        :arg str grid_square: The Maidenhead grid square locator.
+        :rtype: tuple
+        :returns: The latitude-longitude coordinates in a tuple.
+        """
+
+        m = re.match(r"^[A-X][A-X][0-9][0-9]$", grid_square)
+        if(m):
+            gs = m.group(0)
+            latitude = self.latitude4(gs)+0.5
+            longitude = self.longitude4(gs)+1.0
+        else:
+            m = re.match(r"^[A-X][A-X][0-9][0-9][a-x][a-x]$", grid_square)
+            if(m):
+                gs = m.group(0)
+                latitude = self.latitude4(gs) + (1.0/60.0)*2.5*(ord(gs[5])-ord("a")+0.5)
+                longitude = self.longitude4(gs) + (1.0/60.0)*5*(ord(gs[4])-ord("a")+0.5)
+            else:
+                raise ValueError("Unable to parse grid square string.")
+
+        return (latitude, longitude)
+
+    def latitude4(self, g):
+        return 10*(ord(g[1]) - ord("A")) + int(g[3])-90
+
+    def longitude4(self, g):
+        return 20*(ord(g[0]) - ord("A")) + 2*int(g[2])-180
+
+
 class WorldMap:
 
     """ A tool for visualising the world map. """
@@ -83,6 +149,8 @@ class WorldMap:
             self.fig = matplotlib.figure.Figure()
             self.canvas = FigureCanvas(self.fig)  # For embedding in the Gtk application
             self.builder.get_object("worldmap").pack_start(self.canvas, True, True, 0)
+            toolbar = NavigationToolbar(self.canvas, self.application.window)
+            self.builder.get_object("worldmap").pack_start(toolbar, False, False, 0)
             self.refresh_event = GObject.timeout_add(1800000, self.draw)  # Re-draw the world map automatically after 30 minutes (if the world map tool is visible).
 
         # Add the QTH coordinates for plotting, if available.
@@ -99,6 +167,9 @@ class WorldMap:
                 except ValueError:
                     logging.warning("Unable to get the QTH name, latitude and/or longitude. The QTH will not be pinpointed on the world map. Check preferences?")
 
+        self.maidenhead = Maidenhead()
+        self.grid_square_count = numpy.zeros((len(self.maidenhead.upper), len(self.maidenhead.upper)), dtype=bool)
+
         self.builder.get_object("worldmap").show_all()
 
         logging.debug("World map ready!")
@@ -212,6 +283,21 @@ class WorldMap:
                         ax.plot(p.longitude, p.latitude, p.style, transform=cartopy.crs.PlateCarree())
                         ax.text(p.longitude+0.02*p.longitude, p.latitude+0.02*p.latitude, p.name, color="white", size="small", weight="bold")
 
+                # Draw Maidenhead grid squares.
+                xx = numpy.linspace(-180, 180, len(list(self.maidenhead.upper))+1)
+                yy = numpy.linspace(-90, 90, len(list(self.maidenhead.upper))+1)
+                A = self.grid_square_count.copy()
+                A[10, 10] = True
+                A[12, 12] = True
+                A[10, 5] = True
+                A[9, 5] = True
+                z = numpy.ma.masked_array(A, A == 0)
+                ax.pcolormesh(xx, yy, z, transform=cartopy.crs.PlateCarree(), cmap='Purples', vmin=0, vmax=1, edgecolors="k", linewidth=2, alpha=0.6)
+                for i in range(len(self.maidenhead.upper)):
+                    for j in range(len(self.maidenhead.upper)):
+                        text = self.maidenhead.upper[i]+self.maidenhead.upper[j]
+                        ax.text((xx[i]+xx[i+1])/2.0, (yy[j]+yy[j+1])/2.0, text, ha="center", va="center", size=8, color="w")
+
                 return True
         else:
             return False  # Don't try to re-draw the canvas if the necessary modules to do so could not be imported.