Question

After read the google map javascript v3 api,I found I am confused about some concepts of the map type and layers.

For example,google provide some built-in map types:

• 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.

But there are also other types like traffic layer,what’s the difference?

It seems that some of them can only displayed one once while some of them can displayed together(overlayed).

Any one can tell me more details?

UPDATE:

In fact,I am working at a project which want to build our own map api for offline using,we need display more than one layers for one map type.

For example,we have two map tpyes:vector like the google’s RoadMap, and the SATELLITE.

When we show the vecotor type,there are DEM/river/road layers which should be overlayed.

I try to refer to google’s idea,but I can not understand it.

Answer 1

Yes, from what I can gather of your understanding of the concept, it is correct. If you fire up google maps, you’ll see how this is implemented.

Map types are what the actual map image looks like. I.e. whether it is a road map, or satellite photos, etc.

Layers are stuff that can be added on top of those images, such as traffic info (not roads, but roadwork, queues, etc)