RF Propagation: Site Viewer

When using Site Viewer I get the following error: Range is set to maximum propagation distance, which is Earth's radius, 6371km?

[Jacob Halbrooks]

This is a limit in the tool. Can you describe what you you are doing to encounter this limit? For example, are you modelling a transmitter that you expect to have a coverage area greater than the limit?

[Xolani Maxama]

Yes, I am modelling a transmitter, the following is the Matlab command I used:

fq = 410e6; y = design(yagiUda,fq); y.Tilt = 90; y.TiltAxis = 'y'; tx = txsite('Name','Vioosdrift',... 'Latitude', -29.00888889, ... 'Longitude', 17.82388889, ... 'Antenna', y, ... 'AntennaHeight', 60, ... 'TransmitterFrequency', fq, ... 'TransmitterPower', 30); coverage(tx)

Following this, Site Viewer does open up but the coverage plot diagram I get seems out of scale. It's usually large.

Answer 1

[Jacob Halbrooks]

I can run the code you provided but do not encounter an error. The coverage map that results depends on whether the MATLAB release supports terrain. Before terrain support (R2017b and R2018a), the coverage map is large and idealized, reflecting only free-space path loss and the antenna pattern:

However, with terrain I see a more realistic looking coverage map, since the Longley-Rice model is used which includes loss due to terrain blockage and diffraction. For example, here is the coverage map running from R2019a:

Note that here the range of the coverage map is 30 km by default, which results in the smooth edge on the right-hand side. You can specify the "MaxRange" parameter to control the coverage map area. For example:

>> coverage(tx,'MaxRange',100000)

[Xolani Maxama]

I use version R2018a, i get the first coverage map, where the coverage is large and idealized. Should i rather get a newer version R2019a?

[Jacob Halbrooks]

I recommend you upgrade to R2019a for terrain features with RF Propagation. In addition to default access to terrain data (Internet required) which I used to generate the coverage map above, you can also import DTED terrain using the new addCustomTerrain function. A couple of other new features you may be interested in are the ability to visualize the 3D radiation pattern on the map (see here) and ability to have multiple Site Viewer windows with programmatic control (see here).

Answer 2

[Xolani Maxama]

Thank you so much Jacob! It does work after importing the DTED files using the addCustomTerrain function in version R2019a.

Im just working on finding the DTED file for my area in South Africa, with the following coordinates:

Latitude', -29.00888889, ...

'Longitude', 17.82388889....

I tried the following command and got a dt0 file:

latlim = [ -29.00 30.90];

lonlim = [17.95 19.10];

dteds(latlim, lonlim)

ans =

180×1 cell array

{'dted\e017\s29.dt0'}

{'dted\e018\s29.dt0'}

now, when adding the file

addCustomTerrain('mydted','e017_s29_30arc_v0.dt0')

Matlab is unable to load file. am I missing a step or is this the wrong file format?

[Jacob Halbrooks]

Do you have the 'e017_s29_30arc_v0.dt0' file that was specified? Note that "dteds" returns names assuming that they correspond to a regular set of DTED files that you must acquire separately. The files are not included in MATLAB.

A good source of DTED files is the USGS through EarthExplorer. You can select a location in the map, click "Data Sets", then expand "Digital Elevation" and "SRTM" to find data sets that are available in DTED format.

[Xolani Maxama]

I dont have the file. Okay, I will source it from USGS then and let you know how it goes.

Thanks again!

Answer 3

[Xolani Maxama]

Hi Jacob!

I finally got it right! I downloaded the files like you said and added them to Matlab-it now works!

Thanks alot!

Answer 4

[Xolani Maxama]

Hi again Jacob,

Just one more question...

I am trying to read more than one of the dted files at once so that I can see the coverage. Right now, i can only see one area at a time. how do i combine all 4 files so that i can see the area i want.

The files i have added are:

addCustomTerrain('mydted','s29_e017_1arc_v3.dt2')

addCustomTerrain('mydted1','s29_e018_1arc_v3.dt2')

addCustomTerrain('mydted2','s30_e017_1arc_v3.dt2')

addCustomTerrain('mydted3','s30_e018_1arc_v3.dt2')

[Jacob Halbrooks]

You can pass multiple DTED files into a single call to addCustomTerrain by specifying them as a string array or as a cell array of char vectors. In your case, this should work:

addCustomTerrain('mydteds',{'s29_e017_1arc_v3.dt2','s29_e018_1arc_v3.dt2','s30_e017_1arc_v3.dt2','s30_e018_1arc_v3.dt2'})

[Xolani Maxama]

Thanks Jacob!