How will we know if a speed reading is accurate?

I have been recording tracks on my GPS and finding anomalies that will show me suddenly sailing about twice or three or four times the actual speed. These anomalies are cast out when I mention my max speed.

The max speed indicator on my gps does not know how to eliminate anomalies, bogus readings. So I find that the max speed feature on my gps is useless. When I upload data tracks to my computer and analyze a track for highest speed, I need to find a series of readings that are somewhat similar. If I see a series of speed registrations that are all within a few percent of one another, then I'll trust them. But when I see 6,9,8,9,7,6,7,7,9,14,7,6,6, .. Well then I am going to cast out that unusually high reading. Too bad the max speed log would not be able to do the same!

If you are reporting your max speed from a single momentary reading, or from a max speed log, then it is very likely that you are believing a reading that is erroneous, an anomaly.

How can we know if a reading is accurate or if it is just erroneous?

GARY