HMR File

The 256 byte header contains information that is vital to processing and must be filled in. The C/C++ structure definition of the HMR header is as follows:

HMR Header Struct Definition
Word	Size	Type	Definition
szTitleStr	12	char[12]	“$IMUHEADING\0” – NULL terminated ASCII string
ucType	1	uint8_t	1 = values from external source 2 = values form dual antenna source
dBoreSightRotationZ	8	double	Heading boresight between the forward direction of travel and the vector between antennas. Positive rotation is clockwise about Z
dBoreSightRotationZStdDev	8	double	Accuracy of the boresight, 0.0 if not known
Extra	227	int8_t[227]	Reserved for future use

The single header is then followed by the 34-byte structure type below for each heading update record:

HMR Record Struct Definition
Word	Size	Type	Definition
dGpsTime	8	double	GPS seconds of week
sGpsWeek	2	int16_t	GPS week
dHeading	8	double	The heading update value in decimal degrees, positive rotation is clockwise from North
fHeadingStdDev	4	float	Standard deviation of the update in decimal degrees., 0.0 if not known
fBaselineLength	4	float	Distance between antennas in meters. Only use if ucType == 2
fPitch	4	float	Pitch between the two antennas in decimal degrees. Only use if ucType == 2
fPitchStdDev	4	float	Standard deviation of the pitch in decimal degrees, 0.0 if not known