On many tourist spots in China you an rent an electronic audioguide. Some of these attractions have an extra cool guide, it shows a small map of the area and shows you where you are and what parts you haven't seen yet. The map is a simple plastic covered paper map on the front of the device with red leds behind it, visible through holes in the map. There are no buttons and your own location is indicated only by a flishing light on the spot where you last listened to an explanation. But simple as it is, it works great.
灵隐寺 (the Lingyin temple) in 杭州 (Hangzhou) is one of the larger temples covering a large area. Outside the temple there are a number of buddha statues carved into the rock of the mountain (dating back to Yuan dynasty). So they area is pretty large and the sites to see are dispersed. They rent out audio guides which show a little map of the area. When you get the device it shows a red led light on all locations on the map where you can listen to an explanation. Your own location is indicated by a blinking led light. If you have listened to an explanation the led corresponding to the location switches of.Geotag (location) for:
It works pretty simple. As soon as you are within the coverage of a transmitter near a site the guide starts to play the corresponding text. So the transmitter only needs to broadcast a message like “play text two”. From my experiences with the guides it does not need line of sight. So it does not seem to use infrared or light. I assume it uses a low power radio transmitter. Given the area it needs to cover it might be using a bluetooth frequency and protocol.
They rent out the same type of guide in the 故宫 in 北京. However, since the pavilions there are actually closer to eachother than the sites at 灵隐寺 it sometimes starts to playing a text about a pavilion when your still inside the previous one. As a result one tends to run to the next pavilion as soon as the corresponding text starts.
So you can see in one glance which parts of the area your have not seen yet. The little device combines three functions in one: an audio guide, a map of the area and a log of the places you have seen already.Geotag (location) for: