As Haggai said,

This is a little patch for Ext.ux.GMapPanel3.js

Change lines 273 and 284 by
this.gmap = new google.maps.Map(this.body.dom,  {zoom:this.zoomLevel,mapTypeId:  (this.gmapTypeId!=undefined?eval(this.gmapTypeId):google.maps.MapTypeId.ROADMAP)});

This is to allow you to change the style of the map :

  • MapTypeId.ROADMAP displays the default road map view
  • MapTypeId.SATELLITE displays Google Earth satellite images
  • MapTypeId.HYBRID displays a mixture of normal and satellite views
  • MapTypeId.TERRAIN displays a physical map based on terrain information

You can now add this line in your gmappanel declarationgmap

TypeId: 'google.maps.MapTypeId.TERRAIN',
by exemple to show a physical map