For dive computers where the reference time (epoch) of the device is
unknown, libdivecomputer uses the current time of the device (devtime)
and the host system (systime) to synchronize both clocks.
Currently, both timestamps are passed directly to the constructor of the
parser. With the new public function, the application can adjust the
timestamps afterwards.
Some dive computers store the depth as an absolute pressure value (in
bar). To convert to a depth value (in meters), the atmospheric pressure
and water density are required. For dive computers that do not have
those values available, libdivecomputer uses a default value. With the
new public api functions, applications can adjust those default values.
Some dive computers already provided a backend specific calibration
function. Those functions are now deprecated. They are kept around to
maintain backwards compatibility for now, but they will be removed in
the next version.
For manual depth calculations by divers, the standard gravity is
often approximated as 10.0 (e.g. 1 bar corresponds to 10 meter), but
libdivecomputer prefers to use the exact value of 9.80665 m/s².
For the McLean Extreme, it has been confirmed that the device also uses
the correct standard gravity internally for the conversion of the sample
depth.
Prefer SI units for internal constants (e.g. density) and calculations.
This results in more consistent conversion formulas across the different
backends.
For the Uwatec backend, this changes makes it also much more visible
that the unit for the depth is either 1 millibar (maximum depth) or 2
millibar (sample depth).
The difference between two unsigned integers can be negative. To avoid
ending up with some very large positive values, an explicit cast to a
signed integer is required.
Depths are normally expected to be always positive, but near the surface
the pressure will be very close to the atmospheric pressure. Therefore
small negative values are not unusual.
The McLean Extreme records a sample every 10 seconds instead of every 20
seconds. This resulted in dive durations that were twice as long as
expected.
Reported-by: David Carron <david_de_carron@hotmail.com>
