ardupilot/libraries/AP_Logger

Logger Notes

Format Types

The format type specifies the amount of storage required for the entry and how the content should be interpreted.

Char	C Type
a	int16_t[32]
b	int8_t
B	uint8_t
h	int16_t
H	uint16_t
i	int32_t
I	uint32_t
f	float
d	double
n	char[4]
N	char[16]
Z	char[64]
L	int32_t latitude/longitude (so -35.1332423 becomes -351332423)
M	uint8_t flight mode
q	int64_t
Q	uint64_t
g	float16_t

Legacy field types - do not use. These have been replaced by using the base C type and an appropriate multiplier column entry.

Char	CType+Mult
c	int16_t * 100
C	uint16_t * 100
e	int32_t * 100
E	uint32_t * 100

Units

All units here should be base units. This means battery capacity uses "amp * second" not "milliAmp * hours". Please keep the names consistent with Tools/autotest/param_metadata/param.py:33

Char	Unit Abbrev.	Description	Notes
'-'	""	no units e.g. Pi or a string
'?'	"UNKNOWN"	Units which haven't been worked out yet....
'A'	"A"	Ampere
'd'	"deg"	of the angular variety	-180 to 180
'b'	"B"	bytes
'B'	"B/s"	bytes per second
'k'	"deg/s"	degrees per second	Not an SI unit, but in some situations more user-friendly than radians per second
'D'	"deglatitude"	degrees of latitude
'e'	"deg/s/s"	degrees per second per second	Not an SI unit, but in some situations more user-friendly than radians per second^2
'E'	"rad/s"	radians per second
'G'	"Gauss"	Gauss	Not an SI unit, but 1 tesla = 10000 gauss so a simple replacement is not possible here
'h'	"degheading"	0.? to 359.?
'i'	"A.s"	Ampere second
'J'	"W.s"	Joule (Watt second)
'l'	"l"	litres
'L'	"rad/s/s"	radians per second per second
'm'	"m"	metres
'n'	"m/s"	metres per second
'N'	"N"	Newton
'o'	"m/s/s"	metres per second per second
'O'	"degC"	degrees Celsius	Not an SI unit, but Kelvin is too cumbersome for most users
'%'	"%"	percent
'S'	"satellites"	number of satellites
's'	"s"	seconds
'q'	"rpm"	revolutions per minute	Not an SI unit, but sometimes more intuitive than Hertz
'r'	"rad"	radians
't'	"N.m"	Newton meters	torque
'U'	"deglongitude"	degrees of longitude
'u'	"ppm"	pulses per minute
'v'	"V"	Volt
'P'	"Pa"	Pascal
'w'	"Ohm"	Ohm
'W'	"W"	watt
'X'	"W.h"	watt hour
'Y'	"us"	pulse width modulation in microseconds
'z'	"Hz"	Hertz
'#'	"instance"	(e.g.)Sensor instance number

Multipliers

This multiplier information applies to the raw value present in the log. Any adjustment implied by the format field (e.g. the "centi" in "centidegrees" is IGNORED for the purposes of scaling. Essentially "format" simply tells you the C-type, and format-type h (int16_t) is equivalent to format-type c (int16_t*100) tl;dr a GCS shouldn't/mustn't infer any scaling from the unit name

Char	Multiplier	Description
'-'	0	no multiplier e.g. char[4]
'?'	1	multipliers which haven't been worked out yet
'2'	1e2
'1'	1e1
'0'	1e0	x1
'A'	1e-1
'B'	1e-2
'C'	1e-3
'D'	1e-4
'E'	1e-5
'F'	1e-6
'G'	1e-7
'I'	1e-9
'!'	3.6	(milliampere * hour => ampere * second) and (km/h => m/s)
'/'	3600	(ampere * hour => ampere * second)