Absorption losses of different terrain types - RF Cafe Forums

 Post subject: Absorption losses of different terrain types

Posted: Thu Feb 07, 2008 8:48 pm 

Hello,

I am modelling an EDACS system operating at 900MHz in Mentum Planet and would like to use the clutter (map of various terrain types) file for the area to improve the accuaracy of my coverage plots. To do this I need to know the absorption losses at 900MHz for various terrain type such as:

Fresh water
Sea Water
Forest
Dry ground
Residential
Dense Urban
Core urban (whatever that is)
Industrial

Can anyone lead me towards some information on this?

Regards,

Gavin Hill

 Post subject:

Posted: Mon Feb 11, 2008 6:08 am 

Hi Gavin
I have contacted a few Planet users to get some help on this one. Do you really mean absorption by these media or do you mean the permittivity and loss factor on reflection from their surfaces?

 Post subject:

Posted: Mon Feb 11, 2008 8:13 pm 

Hi Nubbage,

Thanks for looking into this, as I understand it the 'clutter absorption loss' is the loss resulting from absorption by foilage, buildings, etc which is added to the path loss, or vice versa subtracted from the signal strength. So I think your description is probably more apt, although the permittivity at 900MHz will have little effect.

In Planet (Ver 4.3) the setting I am changing is in
'Propagation Model Properties' under the
'Clutter Properties' tab where I select
'Edit CPA'.
This brings up a table with the various terrain types that I noted in my first post. The variables that I am changing are under the
'Clutter Absorption Loss (dB)' heading.

Regards,

Gavin

 Post subject:

Posted: Tue Feb 12, 2008 10:48 am 

Hi Gavin
I have received unhelpful feedback on my enquiries into the settings for Planet. The most helpful was "to consult the manual", the least helpful was "to enquire at the British Museum" (the group use the very latest software at a world-famous Swedish system manufacturer).
More helpfully, I offer you a French graph of forest attenuation which agrees well with another source I have. This predicts 11dB/100m in winter (assuming deciduous trees with no leaves) and 22dB/100m in summer with wet leaves at 900MHz. There is also a polarization dependence, but the above figures are for vertical pol, normally used for mobile coms.
I will up-load my graph via image-shack as the clip board is ineffective on this site.
Although not strictly valid below 1000MHz, there are good design parameters for rolling terrain and sea paths in the ITU Radio division report ITU-R PN.530. Parameters for urban clutter have been hotly debated for years and I am now not so sure where the debate has led by today. More next posting.

 Post subject:

Posted: Tue Feb 12, 2008 11:04 am 

Here is the graph.
http://img86.imageshack.us/img86/7826/attntreessj1.jpg


Hope that works

 Post subject:

Posted: Thu Feb 14, 2008 8:04 pm 

Hi Nubbage,

Thanks for the feedback, I think the graph will prove to be very helpful. As for the Planet user who suggested "Use the manual", I have, and there are no indications for absorption losses at different frequencies.

Regards,

Gavin