[TowerTalk] Terrain data for HFTA

["Felipe J. Hernández"]

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.

For me extracting from google was a little painful but rewarding, after 
i remodeled the terrain
with the information, my antennas and real life experience on the bands 
started to make sense.

I took samples every 10 ft very close to the antennas and then moved to 
25 ft.

Felipe
NP4Z


On 8/17/2011 2:29 PM, RDStraw wrote:
> Charlie:
>
> 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
> goofy!
>
> 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.
>>>
>>> Grant KZ1W
>> Date: Wed, 17 Aug 2011 06:24:03 -0400
>> From: Pete Smith<n4zr at contesting.com>
>> Subject: Re: [TowerTalk] grabbing terrain data for HFTA
>> To: Charlie Carroll<k1xx at cfl.rr.com>
>> Cc: towertalk at contesting.com, Grant Saviers<grants2 at pacbell.net>
>> Message-ID:<4E4B96C3.5000904 at contesting.com>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> Charlie, this sounds like an excellent solution - potentially much less
>> involved than the old way of using MicroDem and the USGS website.  If
>> you can provide a few more details, I'll be glad to write it up, and I'd
>> bet that N6BV and the ARRL will be interested in making it available on
>> the ARRL web-site.  Dean and I wrote most of the old instructions you'll
>> find, but it always was a PITA because USGS kept changing their web-site.
>>
>> 73, Pete N4ZR
> Grant/Pete:
>
> N6BV: This is the latest operating instructions for HFTA, dated Aug 3, 2009.
> I checked the links for obtaining DEM, NED and SRTM data and they all work.
>
> http://www.arrl.org/files/file/Product%20Notes/Antenna%20Book/HFTA.pdf
>
> Grant: It may be useful for you to check out a webinar I gave. It's entitled
> "Hinks and Kinks for Using HFTA" and can be found on the PVRC website:
>
> http://www.pvrc.org/webinar/webinars.htm
>
> 73, Dean, N6BV
>
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