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1. [TowerTalk] Terrain data for HFTA (score: 1): Author: "RDStraw" <n6bv@arrl.net>; Date: Wed, 17 Aug 2011 11:29:16 -0700; Charlie: You said recently: N6BV: I'm not sure where Google Earth gets their terrain data, but I am suspicious that it is derived at least partially from the SRTM (Shuttle Radar Topography Mission) d; /archives//html/Towertalk/2011-08/msg00183.html (10,028 bytes)
2. Re: [TowerTalk] Terrain data for HFTA (score: 1): Author: "David J. Sourdis - HK1A" <hk1kxa@hotmail.com>; Date: Fri, 19 Aug 2011 22:47:54 -0500; I would not trust Google-Earth elevation data.To add an example like Bimini, Bahamas: Check Malpelo Island, HK0TU, 400 km away from the colombian Pacific coast (4.0 N, 81.6 W) According to Google ear; /archives//html/Towertalk/2011-08/msg00225.html (9,904 bytes)
3. Re: [TowerTalk] Terrain data for HFTA (score: 1): Author: TexasRF@aol.com; Date: Sat, 20 Aug 2011 07:53:04 -0400 (EDT); Sounds like someone's earth bulge corrections are amiss! This is the name used due to the earth shape being slightly ellipsoid instead of a perfect sphere. The earth diameter is slightly greater at t; /archives//html/Towertalk/2011-08/msg00227.html (10,877 bytes)
4. Re: [TowerTalk] Terrain data for HFTA (score: 1): Author: Jim Lux <jimlux@earthlink.net>; Date: Sat, 20 Aug 2011 07:32:24 -0700; Slightly? some 25 km, more like it. (1 part in 286, roughly) (the peak of Everest is not the farthest point from the Earth's center... Chimborazo in Ecuador is, because it's right on the Equator. Kil; /archives//html/Towertalk/2011-08/msg00232.html (12,559 bytes)
5. Re: [TowerTalk] Terrain data for HFTA (score: 1): Author: "Felipe J. Hernández" <fhdez@vpnet.net>; Date: Sat, 20 Aug 2011 08:00:10 -0400; Dean, Me too would like to take that data from google. In my case ive found that the data from SRTM is never true to my terrain. I trust google earth because it gives me the exact contour and height.; /archives//html/Towertalk/2011-08/msg00240.html (12,548 bytes)
6. Re: [TowerTalk] Terrain data for HFTA (score: 1): Author: Máximo EA1DDO_HK1H <ea1ddo@hotmail.com>; Date: Sun, 21 Aug 2011 10:10:18 +0000; Hi all, Actualy the DEM data with world coverage is limited, low quality. To find good quality (high definition) DEM data we need to go country by country DEM, I meant, every country seems to have hi; /archives//html/Towertalk/2011-08/msg00246.html (14,791 bytes)
7. Re: [TowerTalk] Terrain data for HFTA (score: 1): Author: Michael Tope <W4EF@dellroy.com>; Date: Sun, 21 Aug 2011 14:55:06 -0700; Using the Radio Mobile program, I found the SRTM 1 arcsecond elevation data to match very well with GPS readings I took in the high desert area just north of Los Angeles (to within a few feet typical; /archives//html/Towertalk/2011-08/msg00254.html (13,655 bytes)
8. Re: [TowerTalk] Terrain data for HFTA (score: 1): Author: Jim Lux <jimlux@earthlink.net>; Date: Sun, 21 Aug 2011 16:22:53 -0700; If there's a big discrepancy between SRTM and "on the ground", I'd look for mismatches between the reference ellipsoid that SRTM uses and local sea level datum. There can be surprisingly big differen; /archives//html/Towertalk/2011-08/msg00256.html (10,657 bytes)
9. Re: [TowerTalk] Terrain data for HFTA (score: 1): Author: Michael Tope <W4EF@dellroy.com>; Date: Sun, 21 Aug 2011 17:05:26 -0700; What you describe, Jim, seems like a likely explanation for large scale offsets. A good check of a location like Felipe's which shows large absolute errors between GPS and SRTM would be to compare tw; /archives//html/Towertalk/2011-08/msg00259.html (12,912 bytes)
10. Re: [TowerTalk] Terrain data for HFTA (score: 1): Author: Jim Brown <jim@audiosystemsgroup.com>; Date: Mon, 22 Aug 2011 08:36:34 -0700; Those following this discussion should know that Jim Lux and Michael Tope are engineers at JPL, and thus more likely than most of us to know the facts here. When either of them says anything, i sit u; /archives//html/Towertalk/2011-08/msg00268.html (8,770 bytes)
11. Re: [TowerTalk] Terrain data for HFTA (score: 1): Author: Jim Lux <jimlux@earthlink.net>; Date: Mon, 22 Aug 2011 15:57:09 -0700; I think that's a good example of which ellipsoid is being used. if you move your cursor across some of the islands (little more than rocks sticking up, it looks like) at 3-49-57.46 N 81-36-15.28W it; /archives//html/Towertalk/2011-08/msg00275.html (9,280 bytes)
12. Re: [TowerTalk] Terrain data for HFTA (score: 1): Author: "Terry G. Glagowski" <TGlagowski@SBCglobal.net>; Date: Sat, 27 Aug 2011 20:37:40 -0400; Suggest you check... Wikipedia for WGS84 http://en.wikipedia.org/wiki/World_Geodetic_System Wikipedia for NAD83 http://en.wikipedia.org/wiki/North_American_Datum Coordinate Converter http://home.hiwa; /archives//html/Towertalk/2011-08/msg00411.html (59,521 bytes)

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