[TowerTalk] HFTA Question

[cqtestk4xs at aol.com]

I've used N6BV's HFTA for over 15 years, love it and found it very useful.
Recently I downloaded the terrain from K6TU for a new planned station in V31 and found some strange numbers.  All latitude and longitude numbers were double checked so that is not an issue.  From being in the area where the station will be located and from the Google Earth terrain numbers, things don't agree.  I'm talking about 50 foot hills that don't exist.  From observation, I know there is a steady slow slope to the ocean from an elevation of 45 feet to ocean level 2500 ft away.  No hills, and Google Earth confirms this, but the terrain numbers from K6TU claims there is one
I manually downloaded the numbers for several different directions and compared the output between the numbers from K6TU and the ones from Google and there are differences.  No gross changes, but enough to change the output by 3 or more dB in many cases.  I'm not badmouthing  K6TU and appreciate his work, but this is quite puzzling.  I've never had this happen before.  In low flat sugar cane areas, Google gives numbers that conform, but the numbers I got from K6TU  show rises of almost 40 ft.
My guess is that the numbers outside the US are not quite as accurate and perhaps  thick jungle gives an artificial height.  Any thoughts?
Bill K4XS/KH7XS