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Appendix A - Metadata Commands in SDI-12 version 1.4
Revision 1.4 of the SDI-12 specification, released in May of 2017, adds a set of commands
to access metadata – descriptions of the returned data including SHEF codes and units. The
Smart PT sensor implements the 1.4 specification.
aIM0!
a00002
aIM0_001!
0,PW,BAR,pressure;
aIM0_002!
0,TW,DC,temperature;
Appendix B – Calculation of depth
Depth is computed as follows
depth = depth * (9.80665 / gravity) * (1000 / density)
If density is set to 1, the Smart PT will apply a temperature correction:
density = (999.83952 + 16.945176*t - .0079870401*t*t - 0.000046170461*t*t*t +
0.00000010556302*t*t*t*t - 0.00000000008054253*t*t*t*t*t) / (1 + .016897850*t);
If density is set to a value other than 1, that value will override the temperature correction.
If top of casing is greater than zero, depth is subtracted from top of casing:
depth = top of casing - depth
Finally, offset is added to the depth value:
depth = depth + offset
