Using GPS coordinates (when on a rooftop) and antenna height


When using the GPS coordinates that was taken while on a rooftop for example, does LINKPlanner use the height of the building (known by the GPS) and adds this to the overall subscriber antenna height?  Rather than the ground earth height. 

Should we assume that the LINKPlanner calculations will use the roof's height automatically in its calculation and therefore should only enter the subscribers antenna height based on the height from the rooftop itself rather than from the ground.

So for example, if I were to take my GPS coordinates from on top of the building's roof (rooftop height say 40ft), enter these GPS coordinates in LINKPlanner and then make my subscriber antenna height 10ft.  Will LINKPlanner see that the overall subscriber antenna height is now at 50ft (plus any geographic elevation)?

Or, do I enter 50ft in the subscriber antenna height, since from the ground to the antenna height will about 50ft?

Note, I saw in an earlier post and response from Cambium, that LINKPlanner will automatically create a profile showing the elevation and the subscriber antenna height entered to compute and show the complete path profile.  Just not sure if it also takes into account man made structures such as buildings.


Linkplanner will only consider the terrain, not buildings or vegetation. So in your example, your building roof is 40ft AGL, and your antenna mounted a further 10ft . You should set the Antenna Height to 50ft.

Remember to also set the Maximum Height in the Site Details section. If your site Maximum Height is say 10ft, and you set the Antenna Height at 50ft, it will appear red (although it will still calculate the link using the 50ft height).

Man-made structures can be added into the profile manually. Double click in the spot you want to add a building and then add an obstruction height. THis will then be displayed on the path profile and Linkplanner will take it into account.

I highly recommend exporting the profile to Google Earth and then you can follow the path, as it shows the Fresnel zone, and then you can add all the obstructions that look like a problem.

Unfortunately there isn't a simple answer for that one. It depends. We try to use the data with the highest resolution for your location, taken from SRTM, Aster or Geobase (see
Since this data is measured from above, it will usually include any features that existed at that time when the measurement was taken, such as buildings, trees, etc. There may be data for each 30 m interval, so we then interpolate the 4 closest points to determine the height at each location. Due to the way that the data is averaged, it should include the height (or almost) for large buildings that occupy several pixels, but if a building (or the trees) only occupy a part of a pixel or overlap two pixels such that there are sample points at ground level as well within the pixel, then the height shown will not be the full height of the building but equally not be true ground level either.

As Kyle mentioned, you should also compare with Google Earth (which isn't always correct either, particularly if it is using the same data source) or perform a site survey to confirm the heights. See

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Another point to consider is that GPS coordinates obtained from a phone or GPS receiver may not provide the most accurate height readings.

You may obtain better results from an altimeter that uses barometric pressure.


Hi David;

Thanks for that tip.


Hi Andrew;

Thank you / Cambium for such a quick follow-up to my question.  The answers and links were very good and improved my understanding on how to use LINKPlanner even more / better.


link planner profile works with the natural earths curvature and does not take into account the man made structures, so one needs to add the height of the mast or building or both if thats the case