NARDA LR-01, User Manual

Page: 166 / 194

9-38 Command protocol
9.5.3.1 Position Information
The 16 bit figure named Latitude int is shown as follows:
Byte
49/50
Degree
N/S V
Minute
The figure named
Latitude int is made of 4 fields and represents the integer part of the GPS Latitude.
•
Degree is a 8 bit unsigned integer which indicates the degree of latitude.
•
N/S (D7) is a flag which indicates whether the latitude is North or South. When referred to North
N/S=0 while if N/S=1 the latitude is South.
•
V
(D6) is a flag, which indicates whether data is valid, or not. When coordinates are valid V=0.
When V=1 the GPS was not able to correctly get the position.
•
Minute is a 6 bit unsigned integer which indicates the minute integer part of latitude.
The 16 bit figure named Latitude Fract is shown as follows:
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Byte
51/52
Ten thousandths of a minute
The figure named
Latitude Fract
is a
Big-endian
unsigned 16 bit integer and indicates the fractionary
part of the GPS Latitude and it is expressed in Ten-thousandths of a minute.
Merging the previous data
Latitude int and this figure the full latitude can be obtained.
If, for example, Latitude int=0x2c04 and Latitude Fract=0x12a9 then the GPS latitude would be:
44 degree, 04.4777 minute North.
Indeed, 0x2c=44, 0x04=04 and 0x12a9=4777. N/S is 0 then the latitude is North.
The 16 bit figure named
Longitude int
is shown as follows:
Byte
53/54
Degree E/W res Minute
The figure named
Longitude int is made of 4 fields and represents the integer part of the GPS Longitude.
•
Degree is a 8 bit unsigned integer which indicates the degree of latitude.
•
E/W (D7) is a flag which indicates whether the Longitude is East or West. When referred to East
E/W=0 while if E/W=1 the Longitude is West.
•
D6 is reserved and have to be masked out.
•
Minute is a 6 bit unsigned integer which indicates the minute integer part of Longitude.
The 16 bit figure named Longitude Fract is shown as follows:
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Byte
55/56
Ten thousandths of a minute
The figure named
Longitude Fract is a Big-endian unsigned 16 bit integer and indicates the fractionary
part of the GPS Longitude and it is expressed in Ten-thousandths of a minute.
Merging the previous data Longitude int and this figure the full Longitude can be obtained.
If, for example, Longitude int=0x0809 and Longitude Fract=0x16b3 then the GPS Longitude would be:
8 degree, 09.4777 minute East.
Note that position is valid only when
Flag V of Latitude int is zero.