Modified draw_graticule method of LayeredBasemap to plot only ticks if...

Modified draw_graticule method of LayeredBasemap to plot only ticks if graticule line width is zero.

git-svn-id: https://svn.seismo.oma.be/svn/seismo/mapping/layeredbasemap/trunk@7715 40b490c5-b4d9-47cb-8714-9bef99b524d5

layered_basemap.py

@@ -2089,7 +2089,7 @@ class LayeredBasemap:
 		"""
 		Draw meridians and parallels according to :prop:`graticule_style`
 		"""
-		# TODO: find a way to plot only ticks and/or parallel/meridian intersections
+		# TODO: find a way to plot only parallel/meridian intersections
 		if self.graticule_style:
 			#if abs(self.region[1] - self.region[0]) == 360:
 			#	labelstyle = "+/-"
@@ -2103,6 +2103,19 @@ class LayeredBasemap:
 				first_meridian = np.ceil(self.region[0] / self.dlon) * self.dlon
 				last_meridian = np.floor(self.region[1] / self.dlon) * self.dlon + self.dlon
 				meridians = np.arange(first_meridian, last_meridian, self.dlon)
+				line_style = meridian_style.line_style
+				if line_style.line_width == 0:
+					## Plot only ticks
+					## see https://stackoverflow.com/questions/18363987/basemap-how-to-remove-actual-lat-lon-lines-while-keeping-the-ticks-on-the-axis/62087643#62087643
+					# convert from degree to map projection
+					lon_ticks_proj, _ = self.map(meridians, np.zeros(len(meridians)))
+					# manually add ticks
+					self.ax.set_xticks(lon_ticks_proj)
+					self.ax.tick_params(axis='x', which='major', length=6, width=1, direction='in')
+					# add ticks to the opposite side as well
+					self.ax.xaxis.set_ticks_position('both')
+					# remove the tick labels
+					self.ax.xaxis.set_ticklabels([])
 				self.map.drawmeridians(meridians, zorder=self.zorder, **style_kwargs)
 			if self.dlat != None:
 				parallel_style = self.graticule_style.copy()
@@ -2112,6 +2125,18 @@ class LayeredBasemap:
 				first_parallel = np.ceil(self.region[2] / self.dlat) * self.dlat
 				last_parallel = np.floor(self.region[3] / self.dlat) * self.dlat + self.dlat
 				parallels = np.arange(first_parallel, last_parallel, self.dlat)
+				line_style = parallel_style.line_style
+				if line_style.line_width == 0:
+					## Plot only ticks
+					# convert from degree to map projection
+					_, lat_ticks_proj = self.map(np.zeros(len(parallels)), parallels)
+					# manually add ticks
+					self.ax.set_yticks(lat_ticks_proj)
+					self.ax.tick_params(axis='y', which='major', length=6, width=1, direction='in')
+					# add ticks to the opposite side as well
+					self.ax.yaxis.set_ticks_position('both')
+					# remove the tick labels
+					self.ax.yaxis.set_ticklabels([])
 				self.map.drawparallels(parallels, zorder=self.zorder, **style_kwargs)
 			self.zorder += 1