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Geomorf - Geographical Model of Radio-Frequency Power Density

Submitted by cdh30 on Tue, 2010-07-06 15:21
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GEOMORF is a GIS-based model, designed to simulate power density around EMF transmitters such as mobile phone masts.

Model description
Purpose: 

 

The Geographical Model of Radio-Frequency Power Density (Goemorf) is a GIS–based exposure model designed to estimate power densities at receptor locations around mobile phone base stations. The model uses a semi-Gaussian formulation to represent spatial variations in power densities around mobile phone masts, on the basis of power output, antenna height, tilt and the surrounding propagation environment.

Boundaries: 

Outdoor exposure

Spatial resolution: address or postcode

Input: 

 

Mx,My
Mast location
metres
x and y co-ordinates of the source mast
Rx,Ry
Receptor location
metres
x and y co-ordinates of the receptor
Em
Elevation of mast
metres
Height of the ground surface above ordnance datum, at the mast location
Er
Elevation of receptor
metres
Height of the ground surface above ordnance datum at the receptor location
Ha
Antenna height
metres
Height of the centre point of the antenna, above the ground surface. Default = surface height + 20 metres.
Hr
Receptor height
Metres
Height of the midpoint of the receptor, above the ground surface.
Tt
Net tilt
degrees
Total tilt due to electrical and mechanical tilt. Default = 6.5o
P
Power output
W
Maximum operational effective isotropic radiated power output of the source antenna
Zb
Azimuth
degrees
Direction (degrees from true north) of the centreline of the mainbeam of the antenna
BWd
Vertical beam width
degrees
Specified vertical beam width of the source antenna Default = 6o.
BWl
Horizontal beam width
degrees
Specified horizontal beam width of the source antenna. Default = 67o.
Tlos
Topographic line of site
 
Topographic line of site from antenna to receptor (0,1); modelled using visibility function in GIS.
C
Land cover type
 
Categorisation of land cover in area surrounding the receptor (urban, forested, open); determined by intersecting land cover data with receptor locations in GIS.
Output: 

Output: Power density (mW/m2)

Data type: point estimate(s)

Data sources: mobile phone operators

Data format: ESRI ArcGIS shape files

Description of processes modelled and of technical details: 
  • Operating System: WINDOWS
  • Software requirements: ArcGIS9.3 + Spatial Analyst extension
  • Programming language: VBA
  • Developed by Imperial College London
  • Model is free to use
  • Intellectual property rights Imperial College London
  • Canned model - cannot be modified
Rationale: 

THe GEOMORF model is based on the free-space equation for electromagnetic radiation, adapted to take account of the reduction in power density both along the beam and transverse to the beam.  The model has been developed and validated on the basis of field measurements made around a series of mobile phone transmission masts (macrocells) in Great Britain, where it was shown to give good approximation of measured power densities (r2 ~0.6) across a wide range of conditions.  In densely built-up urban areas, performance is poorer, due to local variations caused by buildings.