Well, there is Annapurna I and Annapurna South. There is often confusion. Perhaps that might account for the variation. When you list a mountain Summitpost automatically supplies the coordinates. I have to rely on the summitpost coordinates--- last time I was in Nepal we didn't have handy GPS info.
The existing co-ordinates appear to be about a mile south of the summit and is definitely Annnapurna I not very close to Annapurna South I think the latitude is more correctly at the 28.595. I found this at
Terraserver.com (not terraserver.microsoft.com). The longitude is hard to improve upon because of the long east-west ridge.
You can really zoom in on the mtn. at terraserver.com and as you hover the mouse, the coordinates will appear in boxes over to the left of the aeriel photo. For some reason Google Earth messes up this mountain as it does those around Zermatt.
According to http://www.tourism.gov.np/1310peaks.htm (if it is correct (and due to the state of their website it might not be)), shouldn`t the geo coordinates of the peak be:
28.5958, 83.8222 ?
(Where did you get your coordinates from?)
3 February 1987, Jerzy Kukuczka and Artur Hajzer (PL)
Regarding the incorrect coordinates, I believe these may point to a minor peak called Bharha Chuli that is slightly lower and is found between Annapurna I and Annapurna South.
To add to the discussion, I believe the correct coordinates are as follows: