gnsstk::X1Sequence Class Reference

Detailed Description

GPS X1 Sequencer. Applied Research Laboratories, The University of Texas at Austin August 2003

X1Sequence is contains a six-second (four Z-count) sequence of the combined X1A/X1B data for the GPS constellation. The X1 sequence repeats every 1.5s (each X1 epoch) and is identical for all SVs and all 1.5s epochs. In this case, 6 seconds of bitstream is generated and stored because this set of code "thinks" in term of 32-bit words and a 1.5s epoch doesn't contain an integer number of 32-bit words of packed bits) - there's a .25 word (8 bit) remainder. Therefore, a six second seqeunce DOES include an even mulitple of 32 bits, which greatly simplifies handling of the data.

Six seconds of X1 bits is a significant amount of data: X1 Epoch = 4092 X1A bits * 3750 X1A cycles = 15,345,000 bits 6 s = 4 X1 Epoch = 4 * bits = 4 * 15,345,000 = 61,380,000 bits. The number of 32 bit words required equals 61,380,000 bits / 32 bits/word = 1,918,125 words

Definition at line 74 of file X1Sequence.hpp.

#include <X1Sequence.hpp>

Public Member Functions
uint32_t &	operator[] (int i)
const uint32_t &	operator[] (int i) const
	X1Sequence ()
	~X1Sequence ()

Static Public Member Functions
static void	allocateMemory ()
static void	deAllocateMemory ()

Static Private Attributes
static bool	isInit = false
static uint32_t *	X1Bits = 0

Constructor & Destructor Documentation

X1Sequence()

gnsstk::X1Sequence::X1Sequence

(

)

Initialize the member variables associated with this object. In the case of this class, this is a significant amount of work. The X1A/X1B process described in ICD-GPS-200B is followed in order to fill the X1Bits array.

Definition at line 58 of file X1Sequence.cpp.

~X1Sequence()

gnsstk::X1Sequence::~X1Sequence ( )

inline

Definition at line 84 of file X1Sequence.hpp.

Member Function Documentation

allocateMemory()

void gnsstk::X1Sequence::allocateMemory ( )

static

The X1 sequence requires a 6-second buffer of 10MBit/sec samples. This comes to approximately 2 million four-byte unsigned integers. These data are the same for all PRN codes To minimize the memory footprint, these data are stored in a dynamically-allocated static array. It is

• - - - NECESSARY - - - - that the calling method call X1Sequence::allocateMemory() PRIOR to instantiating the first X1Sequence object. X1Sequence::allocateMemory() should only be called once. Violation of either condition will result in a gnsstk::Exception thrown from either X1Sequence::X1Sequence() or X1Sequence::allocateMemory().

The X1Sequence::deAllocateMemory() method may be called to release the memory (if desired) but it should only be called after all X1Sequence objects have been "destroyed".

Definition at line 68 of file X1Sequence.cpp.

deAllocateMemory()

void gnsstk::X1Sequence::deAllocateMemory ( )

static

Definition at line 144 of file X1Sequence.cpp.

operator[]() [1/2]

uint32_t & gnsstk::X1Sequence::operator[] ( int  i )

inline

Definition at line 118 of file X1Sequence.hpp.

operator[]() [2/2]

const uint32_t & gnsstk::X1Sequence::operator[] ( int  i ) const

inline

Given a word number from 0 to NUM_6SEC_WORDS, return the requested word.

Definition at line 123 of file X1Sequence.hpp.

Member Data Documentation

isInit

bool gnsstk::X1Sequence::isInit = false

staticprivate

Definition at line 115 of file X1Sequence.hpp.

X1Bits

uint32_t * gnsstk::X1Sequence::X1Bits = 0

staticprivate

Definition at line 114 of file X1Sequence.hpp.

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The documentation for this class was generated from the following files:

• X1Sequence.hpp
• X1Sequence.cpp