Does any of the RF modeling software automatically compare NED with SRTM
to extrapolate clutter height? It seems like it would be a
straightforward feature to add.
On 7/22/2015 8:35 AM, Hardy, Tim wrote:
Another point to remember:
The end points of an SRTM profile sometimes need to be adjusted downwards (or
at the very least, verified) to account for the morphology above terrain that
may have been included in the SRTM data.
-----Original Message-----
From: Af [mailto:[email protected]] On Behalf Of Brian Webster
Sent: Tuesday, July 21, 2015 11:22 PM
To: [email protected]
Subject: Re: [AFMUG] NED vs SRTM
NED is the national elevation dataset and is based on actual ground elevation
data and digitized topo maps.
SRTM is a combination of RADAR and LIDAR data from the shuttle missions. They
do not reflect actual ground elevation, they are a processed echo return of
whatever radar and LIDAR returns that were received on the shuttle.
The source of the data should also be known as to the resolution. SRTM data was
published at 30 meter resolution meaning the hard data points are spaced at 30
meter intervals. NED data is available in various resolutions the most common
nationwide being 1/3 arc second or 10 meter resolution or actual data points
every 10 meters. This produces a much more accurate terrain model which in turn
creates much more accurate RF propagation information.
I have attached a real rough paper with images that illustrate the various
differences in terrain data and resolution.
Thank You,
Brian Webster
www.wirelessmapping.com
www.Broadband-Mapping.com
-----Original Message-----
From: Af [mailto:[email protected]] On Behalf Of Adam Moffett
Sent: Tuesday, July 21, 2015 6:19 PM
To: [email protected]
Subject: [AFMUG] NED vs SRTM
If there's a 5 meter discrepancy between USGS National Elevation Data and the
Shuttle Radar Topography Mission, who would you trust? Would you bet $500 on it?
In this case, with NED I'll have LOS on a backhaul, and with SRTM I'm in the
woods. I'm under the impression that SRTM sometimes gets you treetops rather
than the ground. If I'm wrong I have alternate paths, but I'd have to pay for
a new PCN....so it really is a $500 bet. :)
