Hey Abhinav,
GPS is received number of string which is contain various information. GPGGA is one of the string received by GPS receiver and it is provide valuable information of location for your application GPS Navigator. In GPGGA string, you get the information longitude and latitude for navigate location. Altitude provide the information of height above sea level. If you want 3D location you need to be all three infromation longitude, latitude and Altitude.
For Example,
your GPGGA string look like appear..
$GPGGA,123545,4657.038,N,014391.000,E,1,08,0.9,685.4,M,46.9,M,,*47
where..
GGA Global Positioning System Fix Data
123545 Fix taken at 12:35:19 UTC
4657.038,N Latitude 48 deg 07.038' N
014391.000,E Longitude 11 deg 31.000' E
1 Fix quality: 0 = invalid
1 = GPS fix (SPS)
2 = DGPS fix
3 = PPS fix
4 = Real Time Kinematic
5 = Float RTK
6 = estimated (dead reckoning) (2.3 feature)
7 = Manual input mode
8 = Simulation mode
08 Number of satellites being tracked
0.9 Horizontal dilution of position
685.4,M Altitude, Meters, above mean sea level
46.9,M Height of geoid (mean sea level) above WGS84
ellipsoid
(empty field) time in seconds since last DGPS update
(empty field) DGPS station ID number
*47 the checksum data, always begins with *
You need to be extract only your required data like longitude and latitude.