Error in distance calculation

[+hzoi]

So I was updating my stats on mygeocachingprofile.com and was surprised to see that I finally had a find farther than 7500 miles: GC2XWP1, A Warrior's View, which mygeocachingprofile.com puts at 7502.27 miles from my house.

 

"That's odd," I thought, "because the site-generated statistics on geocaching.com are essentially a stripped down version of the ones on mygeocachngprofile.com, and per the distance bar graph, I don't have a cache more than 7500 miles from my house."

 

So I checked back on the stats on the website, and sure enough, geocaching.com says my farthest find is GC2XWP1, A Warrior's View, which is 7497.217 miles from my home coordinates.

 

But when I check the cache itself, it says it is 7502.3 miles from my location.

 

I have checked my home coordinates on both websites; both are identical.

 

To make things even stranger, project-gc.com thinks GC2XPW1 is 7,510.53 miles from my house. Again, same coordinates. (And to even further complicate things, GSAK and FindStatGen think the same cache is only 7396.58 miles from me, though that may be because I had different home coordinates set at the time of my find, and of all these platforms, only GSAK recognizes that people move from time to time.)

 

So...

 

...what gives?

Edited January 25, 2017 by hzoi

[Moun10Bike]

It depends on the method used for calculating the distance. Great circle calculations - which are a decent estimate that assume a sphere for the earth and use minimal computational power - will put the estimate at the sub-7500 mile value. This is the distance measurement used by the stats because those numbers need to be crunched for every cache for every profile. Cache pages themselves will use a more accurate but more computationally expensive method that accounts for the bulging of the earth at the equator and lead to the larger distances.

[+hzoi]

OK, that explains the difference between the stats page and the cache page. I was under the impression that Groundspeak now ran mygeocachingprofile, or at least licensed its stats engine for the site. Why then are my stats different between the geocaching.com stats and the mygeocachingprofile.com stats?

[Moun10Bike]

While Groundspeak owns MyGeocachingProfile, we don't do any of the coding or maintenance of the site (the original developers do). I don't have any insight into what method of distance calculation they may be using.

[+hzoi]

Fair enough. Thanks.

 

(And congrats on your MIT cert!)