I appreciate the suggestion above that I perform further testing in order to corroborate the poster’s conclusions. However, it is not additional testing that is needed on my part, it is more complete description of my tests and more definitive characterization of the results and their implementation.
Sometimes, technical discussions are only of partial values as the participants are not in concurrence with the technical definitions of some of the parameters, In this subject, I refer to the term “accuracy” as the difference between an observed value and an accepted, standard value and the term “precision” as the differences between observed values and an accepted, standard value.
https://en.wikipedia.org/wiki/Accuracy_and_precision
1. I performed a test to determine the precision of the barometric function of my GPSr in the absence of weather affects. Typically, in the early daylight hours of my locale, the winds, air movement are non-existent as observed by total lack of tree leaf movement. I recorded the 20 barometrically derived elevations, one every 5 seconds. For that elapsed time of 1 minute and 35 seconds, I assumed that the ambient pressure was constant and any differences in the 20 values of elevation were due to the GPS device’s barometric performance characteristics..
2. I performed another test to determine the precision (more precision = less data scatter) of both the device’s GPS derived elevations and those barometrically derived. I recorded both elevations once daily for 40 days at the exact same location in my backyard. As expected, the barometrically varied due to weather induced ambient pressure changes.
https://en.wikipedia.org/wiki/Normal_distribution
3. Test results: I assumed that the precision of the 3 recorded elevation sets are best defined by their standard deviation values, the lesser being the more precise. That of the first, 1:35 second barometric test, was 1/6 of the 40 day GPS derived value and the 40 day GPS value was 1/12 of the 40 day barometric elevation value. The barometric only (no weather) precision was 6 times better than the GPS derived values which were 12 times more precise than those of the barometric unit values during weather changes. Or, the weather effects degraded the precision barometric elevations by a factor of 72.
When to use barometric: I was asked on another forum which method to use to measure a berm of approximately 50 feet which could be walked down quickly. I know of a nearby hill that professional surveyors had left a mark at the top noting 49 feet and one at the bottom of -2 feet, as measured with their Trimble device. I recorded both GPS and barometric at the top and the bottom, 2 minutes later, during quiescent weather conditions. Subtracting the top elevation from the bottom for both methods resulted in a far better, more precise result for the barometric method after comparing both heights.
When to use GPS methodology; Two possibilities, when there is ongoing weather issues or when many data points are to be recorded. Firstly, if there are weather changes underway, it is likely that all barometric evaluations will be negatively compromised. Secondly, even in quiescent weather conditions, when a number of sequential readings will be recorded for atrack, such as multiple points for total ascent or decent determinations, GPS will be preferred even in quiescent weather conditions. As a manifestation of a normal distribution of the data set, the number of negative value errors will be essentially equal to the number of positive errors. Consequently, the sum of the errors for each recorded elevation will cancel out and the total value of ascent or descent will be as good or better than that of barometrically derived. (Note that there are some GPSr models that cannot automatically record a sequence of GPS derived elevations while traveling.)