HI,
I am new to the arduino world, and doing some research about the following project
found at: http://users.libero.it/riccardo.rocca/07_ROBOAT_2011/roboat2011.html
i have the following questions regarding above project:
Xbee 900 pro isn't available to me, any other alternative? So please recommend me some alternatives, that can be interfaced with the arduino board easily.
Also it will be helpful if you can recommend other GPS Navigation Projects.
What about another xbee such as XBee 2mW Wire Antenna - Series 2 (ZigBee Mesh) - WRL-10414 - SparkFun Electronics
or the RFM module http://www.sparkfun.com/products/11018.
I don't see a camera in your design so you want to keep in sight or it will be gone, across the ocean and around the world. 
cyberstudent:
Xbee 900 pro isn't available to me, any other alternative? So please recommend me some alternatives, that can be interfaced with the arduino board easily.
What sort of range are you aiming for? Is everything working in air - you aren't trying to do radio comms under water, or anything like that?
I need communication only in air, and i am going to use this 433MHz High Sensitivity Transmitter / Receiver Pair found at http://bit.ly/ACRG0c
i wonder if it can be easily interfaced with the arduino? and it supports only one channel for communication? I need two channels one for sending control commands and one for getting the gps sensor data back to the base station? so what should i do in this situation.
plz guide?
With that transmitter (or any other) you can't transmit and recieve at the same time. You need to implement a form of simplex communication where only one transmits at once. This is what the Xbee does for you in its protocol, you will have to do it by hand.