convert tsg.LATX and tsg.LONX from single to double before calling m_grid

this patch correct a bug when m_grid call text with xx & yy arrays with single

tsg_util/plot_map.m

@@ -30,18 +30,23 @@ tsg = getappdata( hTsgGUI, 'tsg_data');
 dateLim = get(hPlotAxes(1), 'Xlim');
 ind = find( tsg.DAYD >= dateLim(1) & tsg.DAYD <= dateLim(2));
 
+% m_grid need the use of double instead single
+% --------------------------------------------
+latx = double(tsg.LATX);
+lonx = double(tsg.LONX);
+
 if ~isempty( ind )
 
-  latMin = min( tsg.LATX(ind) );
+  latMin = min(latx(ind) );
   if latMin < -90
     latMin = -90;
   end
-  latMax = max( tsg.LATX(ind) );
+  latMax = max( latx(ind) );
   if latMax > 90
     latMax = 90;
   end
-  lonMin = min( tsg.LONX(ind) );
-  lonMax = max( tsg.LONX(ind) );
+  lonMin = min( lonx(ind) );
+  lonMax = max( lonx(ind) );
 
   % Oversize window due to the large frame
   %--------------------------------------
@@ -103,8 +108,8 @@ if ~isempty( ind )
 
   % Plot the ship track - Check if LAT-LON in deg-decimal
   % -----------------------------------------------------
-  %m_line(tsg.LONX,tsg.LATX, 'TAG', 'TAG_PLOT4_LINE_SHIPTRACK', 'marker','.','markersize',3,'color','b');
-  %   m_line(tsg.LONX,tsg.LATX, 'LineStyle', 'none', 'marker','*','markersize',2,'color','b');
+  %m_line(lonx, latx, 'TAG', 'TAG_PLOT4_LINE_SHIPTRACK', 'marker','.','markersize',3,'color','b');
+  %   m_line(lonx, latx, 'LineStyle', 'none', 'marker','*','markersize',2,'color','b');
 
   % Plot using QC
   % -------------
@@ -132,8 +137,8 @@ if ~isempty( ind )
       
       % Create line on the map
       % ----------------------
-      m_line( mod(tsg.LONX(ind) + tsg.lonplus, tsg.lonmod) - tsg.lonplus,...
-              tsg.LATX(ind), 'LineStyle', 'none', 'marker','*',...
+      m_line( mod(lonx(ind) + tsg.lonplus, tsg.lonmod) - tsg.lonplus,...
+              latx(ind), 'LineStyle', 'none', 'marker','*',...
               'markersize', 2, 'color', qcColor);
     end
   end