[TowerTalk] Terrain data for HFTA
David J. Sourdis - HK1A
hk1kxa at hotmail.com
Fri Aug 19 20:47:54 PDT 2011
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 earth the island is submerged under the water surface a least 340 ft. In reality, this island has elevations over 1000 ft ASL.
> From: n6bv at arrl.net
> To: towertalk at contesting.com
> Date: Wed, 17 Aug 2011 11:29:16 -0700
> Subject: [TowerTalk] Terrain data for HFTA
> You said recently:
> > Date: Tue, 16 Aug 2011 20:12:45 -0500
> > From: Charlie Carroll <k1xx at cfl.rr.com>
> > Subject: Re: [TowerTalk] grabbing terrain data for HFTA
> > To: Grant Saviers <grants2 at pacbell.net>, towertalk at contesting.com
> > Message-ID: <wg1l6uo0lqvcmp2rougptbc7.1313543269277 at email.android.com>
> > Content-Type: text/plain; charset=utf-8
> > Door's abt to close, so have to be brief. Of late, I have taken
> > to semi-automatically extracting terrain data from Google Earth.
> > I dump this info into an Excel spreadsheet for the number
> > crunching. Pretty painless to do something like ten foot
> > intervals out to 10k feet.
> > 73 charlie, k1xx
> 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) data set. I get nervous when I look at the terrain
> data for islands surrounded by seawater -- which should, by definition, be
> at or at least very close to sea level. It is often shown as being
> considerably different from sealevel.
> N6BV: For example, in Google Earth zoom into Baileytown, Bimini, Bahamas.
> Just to the west of Baileytown the altitude goes considerably negative.
> Either this is a depthsounder reading (which I doubt) or else something is
> N6BV: I'm curious how you are extracting that data from Google Earth
> semi-automatically, even if I'm nervous about the data itself.
> > Grant Saviers <grants2 at pacbell.net> wrote:
> > >Can some one share a pointer for up to date instructions for grabbing
> > >the terrain data from the web for HFTA? Every instruction I've found is
> > >hopelessly out of sync with the current terrain data web site.
> > >
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