thank you for your answer ,and i want to make MESH about altitude information ,so which thing is the best?and what information do i need to make mesh?and do you have MSN? i have more question to ask you ,thank you
As I said you will need the Terrain SDK from Microsoft for that. It contains a lot of information, so I would advice you to read it first.
Most people on forums like this are willing to help you, but you will have to do some reading/searching yourself as well. If it seems you are not doing something with the answers you will get less replies.