Support for ITU-R P.1812-4

[1ntell1gentDB]

Hi Benjamin,

Thanks for this wonderful tool, it will get even better if you consider to addd support for propagation model ITU-R P.1812-4.

With thanks.

[bwinkel]

Hi @1ntell1gentDB,

I looked into this in more detail. The algorithms to calculate LoS, diffraction, troposcatter, and ducting are quite similar in P.452-16 and P.1812-4, but not exactly equal. For example, the latter completely neglects the atmospheric loss terms - which of course don't play a big role at the VHF/UHF frequencies. The biggest difference is in clutter handling. P.452 assumes no clutter in the complete height profile and applies end-point correction. P.1812 adds clutter heights to terrain heights for each position on the propagation path.

Unfortunately, some heavy API changes seem necessary, if one wanted to have several methods offered to the user within the pathprof sub-package. I think, I might do this at some point, but it will certainly take time. A quicker solution would probably be, to use the P.452 algorithm and apply some pre- and post-processing. This will not give the exact same results as P.1812 (at the moment there is no way to leave out the LoS focussing/multipath correction and atmospheric attenuation in pycraf's calculations), but it will be very close. I'm willing to help you implementing the clutter/building entry loss functions of P.1812 as well as the location-percent distribution.

Do you have some example, which we could use for that? I have especially in mind, what database you use for clutter. We'd also need to find a solution for the problem, that SRTM data are in part influenced by clutter (e.g., a forest usually increases the terrain height in SRTM).

[bwinkel]

If I'm not mistaken, P.1812 includes the clutter into the terrain heights of the path (plus some endpoint correction). Applying P.2108 would then do an additional clutter correction, which likely leads to completely overestimated clutter attenuation. Of course, if you don't add clutter heights to the terrain, you could do that.

However, I'd rather modify the output of the height_map_data function - effectively adding the clutter heights to the “height_profs” array. (I'll show you how to do that.) Of course, one needs a database for the clutter in the area of interest. However, as I said, one needs clean topographic data to start with - and SRTM is not clean. An alternative could be to assume that SRTM already contains topography + clutter and just work with that (no additional correction). I'll leave it up to you, which is better for your application. In any case, I don't have access to any other GIS data than SRTM.

Stay tuned.

[1ntell1gentDB]

Hi Benjamin,

Thanks for the clarifications, SRTM is our primary terrain dataset as well, if it already includes clutter, then there is no need to modify height_map_data function in order to add clutter details. Lets stick with SRTM with no additional correction at-least for now.

[bwinkel]

Dear @1ntell1gentDB,

I've finished another tutorial notebook ("03f_pre+postprocessing.ipynb") that shows how you could (roughly) estimate the P.1812 attenuations using pycraf's P.452 implementation. It is completely untested and for now it resides in the "p.1812" branch on the repository. If you want to make use of it, you'll have to install from that branch (pip-install won't work, until I've made another release).

Could you please have a look, and get back to me, if anything is unclear? Note again, the clutter handling is sub-optimal. For one, SRTM is not cleaned for clutter and the other thing is that the P.452 algorithm handles clutter in a different manner, which is not 100% compatible with P.1812. However, it may well be that the errors are negligible - don't know.

At least you get the location-percentage distributions ;-)

[1ntell1gentDB]

Thanks, Ben,

I pulled the 'p.1812' branch for testing as per your suggestions but i encountered some errors during testing. I used the following command for testing it: 'python setup.py test -P p.1812'

Please see the attached log file with the error for your review:
itup1812log.txt

There are also some minor updates on the P.1812-4 calculations froM the ITU, I will send to you the updated MATLAB code and documentations bit late today.

Thanks.

[bwinkel]

Hmm, in that log-file I can't see an error (only compilation/installation debug messages). Since you're using MacOS - have you followed the installation instructions? The default compiler (clang) won't work, but you have to use gcc or llvm. What's the output of gcc -v?

A comparison with MATLAB code would be useful, indeed.

[1ntell1gentDB]

Yes, i did follow all the installation instructions, I am not using the default compiler/clang, I have installed gcc-7.

Please see attached the output of gcc -v
gcc_version.txt

[bwinkel]

Indeed, this looks good.

I just realize that you use a very strange test command - with -P p.1812 you would test a package "p.1812" which doesn't exist. To make the branch active you have to do the following:

git clone https://github.com/bwinkel/pycraf
cd pycraf
git checkout -b p.1812  # make a local branch with name "p.1812"
git merge origin/p.1812  # merge remote branch (github) into local
python setup.py test --remote-data=any

Alternatively, you can download the zipped source distribution of the branch and work with that:

wget https://github.com/bwinkel/pycraf/archive/p.1812.zip
unzip p.1812.zip
cd pycraf-p.1812
python setup.py test --remote-data=any

[bwinkel]

PS: Once the tests were successful, you need to install the package from the source:

python setup.py install

[1ntell1gentDB]

Thanks, the command I am using to test is from your manual specifying testing of specific sub-package installed from the source...

https://bwinkel.github.io/pycraf/install.html

[bwinkel]

Yes, but in this case, the "p.1812" is not a sub-package of pycraf, but just a version of the software. (The modifications will be merged back to the main development branch, once we know, that the tutorial notebook provides more or less correct results.)

[1ntell1gentDB]

Ok, agree, I am also trying to test the same on a Windows machine but it seems the 'setup.py' is missing from the pycraf folder:-)

[bwinkel]

How did you download the sources, via git or downloading the zip?

[1ntell1gentDB]

via git on a console