Millibars (mb or mbar) and hectopascals (hPa) are equivalent Customary units for Altimeter are inches mercury and for SLP it is mb. Then again, other countries may be different.
Aviators know this rule: QNH/Altimeter > QFF/SLP when outside temperature > standard condition temperature - about 15C(at your elevation) and vce versa.
Lat/long...are you comparing minutes/seconds with decimal lat/long? There's 60 seconds in a minute so that why it increases by a minute when seconds > 59.There's probably an online calculator to do a conversion to the desired units.
Re: pressure. You are finding out that when ABS (station presssure) changes, the pressure difference you calculated also changes creating an error. For better accuracy re-calibrate around the average airport pressure (1013.2/29.92). No use calibrating at an extreme high or low.
Ok, well i was calibrating also with the following method you mentioned earlier and thought i was good at only +0.03 hpa.
As for why the SLP pressure Is higher than the elevation pressure at the airport is because the outside standard temperature is less than the standard condition temp of 15C from what you are also saying ? I need to try and understand that some more I guess.
And as for lat and long it is what ambient/cwop is displaying as my location. That needs to be verified. I have no idea what method they are using all i know is it does not match what i have entered in my console
My longitude ends in 32.49 according to google earth etc. and what they have it end is in 32.89 and there is no 89 minutes. Here is the earlier instructions for calibrating that was in your post that I referenced
The following calibration procedure is recommended:
Select a nearby (within 20 miles or 32 km) airport weather station (regional or larger) to provide your reference or calibrated pressure.
Wait for optimal weather conditions to conduct a series of comparisons; these conditions are:
High pressure is nearly overhead
Wind is less than 5 mph (3 m/s), preferably calm
Outside air temperature should relatively stable or slowly changing
Best time to conduct pressure comparisons is in the early afternoon; if the winds are light, then you are reasonably certain high pressure is in the area.
Edit: Unless you live very close to the airport, make sure that you and the airport are in the same pressure system/zone before doing the comparisons.
3. Take a series of four simultaneous pressure measurements using the altimeter pressure from the airport “METAR” report and your barometer:
a) Each comparison should be at least be 15 minutes apart or 1 hr apart for airports that report only hourly.
b) After completing the four comparisons noting your altimeter and the reference airport pressure [differences]; sum the differences between the comparisons and divide by 4 (the number of comparisons) to get a mean difference.
4. If the mean difference between your station and the reference station is more than +/ 00.03 inches for altimeter comparisons, or +/ 1.0 mb; add (or subtract) the difference to correct your altimeter. Repeat the procedure until you achieve the goal of a pressure difference of less than +/ 00.03 inHg or +/ 1.0 mb.
5. Barometers occasionally will “drift” requiring recalibration. Therefore, barometer comparisons (with the Altimeter setting at the airport) should be done at least annually.
