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| GeoCommunity Mailing List |
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| Mailing List Archives |
| Subject: | GISList: radio wave path loss calculation advice |
| Date: |
03/17/2003 10:17:18 AM |
| From: |
GS Rao |
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Andrew Hoppin,
Some years ago we had developed a GIS-based application for TV signal
transmission.
We used telemetry formulae (Fresnel Zone model) to define the zone in which
the signal travels.
The width and length of this zone is defined by the height of the
transmitter and the strength (i.e. power of output) of the signal. Our
project required only point to point transmission. The objective was to
determine the best possible location for a receiver, such that the signal
received had minimal attenuation.
Our software plotted the Fresnel Zone from transmission point radially
outward to a certain distance. It automatically computed the "intersection"
between the zone and the terrain.
For terrain representation we used a digital terrain model, which contained
the following attributes
1) Elevation (to plot terrain profile)
2) Type of land cover (to determine coefficient of signal absorption /
reflection)
3) A table of different coefficients for different land covers.
Using an iterative method, the software plots a series of concentric
circles, with the transmitter at the centre. The receivers are plotted as a
colour-coded symbol along the circumference of each concentric circle. The
colour code reflects the strength of the signal received at each of the
hypothetical receiving points.
Subsequently our customer went into determining the cost of property
acquisition (right of way, cost per square metre etc.). Finally he would
select the most cost-effective location for the receiver.
Hope this helps.
Warm regards
Dr G S Rao
GIS Group
Larsen & Toubro Infotech Ltd.
__________________
Does anyone have experience calculating radio signal attentuation (path
loss) over topography and distance? Any recommendations of
calculations/models/references for how best to do it?
Thanks,
Andrew Hoppin
N Space Labs, Inc.
www.NSpaceLabs.com
andrew@nspacelabs.com
212.219.0851
594 Broadway, #611
NY, NY 10012
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