                     on_success?()
 
         draw_units: (unit_list, opts) ->
+            @clear_all_markers()
             markers = []
             if opts.service?
                 color = colors.service_color(opts.service)

            unitCollection = new UnitCollection()
            unitCollection.fetch(
                success: (collection)=>
                    @clear_all_markers()
                    @draw_units collection, zoom: true, drawMarker: true
                error: ->
                    # TODO: what happens if no models are found with query?

            unit.fetch
                success: =>
                    unit_list = new models.UnitList [unit]
                    @draw_units unit_list, zoom: true, drawMarker: true
                error: ->
                    # TODO: decide where to route if route has invalid unit id.
