gbagua wrote:I am not quite sure about the meaning of those num. 705 029, 691 005.
They are grid references for the topographic maps.
I don't know the area, but I'd suggest you pick up some maps and learn the basics of navigation before walking off-track. Even when using a GPS (or iPhone) you should have paper maps / compass as a back up (and know how to use them), just in case you end up with flat batteries or a lost / broken device. It seems there are a steady stream of people requiring rescues these days because they try walking with just a smart phone...