Some G.P.S devices have electronic maps built in them

Satellites have atomic clocks and transmits radio signals

The G.P.S receiver contacts at least four satellites to act

Modern G.P.S has become more cheaper and more accurate

The word "portable" means you can easily move or carry

Websites usually have visuals that give extra information about the object

Which and that are relative clauses which used in definitions but "which" is more formal.

"eg" is an abbreviation which is used instead of such as

The word "launch" means to sent into space

Homophones are words which sound the same, but have different spelling and different meaning

all websites are useful or reliable

the word "meat" has the same homophone of "meet"

We write definitions to describe a machine or an object

G.P.S receiver is a device which sometimes looks like a mobile

G.P.S system uses infrared signals received from the satellites

The United States Department of Defense designed the system for the military in 1978.

Websites uses visuals to make the reader understand how things work

When we want to find information on a website, we usually use skimming and scanning