When I look into the details of the gateways on the map, I can see that the value “altitude” is interpreted different by the owners:
- often 0: the owner did not care about the value and left the default
- some few meters like 6, 9: the owner interprets the value as “height of antenna above the local ground”
- altitude values that correspond to the altitude above sea level of the local position
Now two questions:
- What is the intended value that should be entered in that field? “height of antenna above local ground” or “altitude of antenna above sea level”
- Is it possible to display a kind of help text or explanation near the input field in the console gateway GUI that helps the users to enter the correct value in that field?
The value should be based on sea level exactly as provided by a GPS receiver (some gateways use GPS to provide the value)
My understanding was same as @kersing, given many GW’s have built in GPS for location. They would have no knowledge of Ant height above local ground. The complication is some will have longer vertical Ant feeder cables so actual emission point may be a few meters higher than detected by GW but given RF losses mean feed should not be too long any error vs GPS might not be too great. Many of mine are not GPS enabled, and may change location for pop-up/coverage tests for demoes/trials etc before any final deployment so (if I remember!) I populate console manually with local ground level above sea-level adding an approx value to reflect Ant height above local ground…so ultimately referenced to sea-level or (again if I remember!) I take a local GPS fix at Ant and use that data (again allow that there may be an error in the GPS value)
Note this becomes useful if you are concerned with building clutter or any intervening terrain issues that might impact the Freznell Zone between GW and any remote node - if you have geo map/meta data for the terrain or a building clutter map you can then model and predict more accurately any potential coverage between target locations…
It is not my understanding, TTN supplied the answer regarding what should be used some time ago. I just couldn’t be bothered to search the forum to supply a link (like the person asking the question didn’t search first.)
Check here for a previous incarnation of the question.