l once read that an acceptable range for a GPS antenna mask angle is between 7° and 15°. I think some people set the angle lower than 7° because they want to grab as many satellites as possible. Last week I used another crew's RTK, and the angle was set to 0°. I have to explain my rationale on this subject to people, so I guess I could point out that although they may be able to grab more satellites, the payoff is not worth the multipath they will be introducing. Is that sound reasoning?
A zero degree mask angle means there's an increased risk of both multipath and increased ionospheric delay/distortion - the lower the SV is on the horizon, the more atmosphere its signal is travelling through to get to your receiver.
For static work, sometimes it makes sense to grab as much data as you can with a zero mask angle, but that's because you'll generally be able to sort out any potential multipath issues during post-processing - or simply apply a custom mask angle during baseline processing to get the results you need.
For RTK work, I don't know that I have ever tested it out. Trimble sets a minimum of 10 degrees for both base and rover, and in my experience I wouldn't expect it to benefit from that small amount of added time in the solution. It's pretty rare to actually be able to see the horizon around here, anyways...
I have always understood the reasoning to be too much added "noise" to the signal when traveling through that much additional atmosphere between the horizon and 10 degrees above. But that may not be the case.
In agreement with both op and follow up. Only two posts when I started to convey the following thought in text...
Additional curiosity: I've wondered if there is any benefit to setting the base mask to a higher value. Say, 20 or 30 degrees.
The thought being, with 4 constellations and total number of satellites available, statistical "repeatability"would not be hindered by the poorer positional determinations involving lower horizon satellites. Which costs time (although it may be inconsequential).
Otherwise spoken, you could achieve faster, reliable base solutions while not compromising robust correction vectors. The end result being tight and quicker surveys.
In other words: would ignoring more fringe satellites in a base solution (higher mask values), and exploiting the shear number of birds in the sky, yield quicker, equally precise and accurate surveying?
Thanks for any thoughts. Apologies for straying from the initial thread. Hope everyone has a better-than-decent day.
How many more satellites do you get in that 10 degrees anyway? Like... 2 or 3? Doesn't seem worth it.
Wow. Yeah static is about the only reason to set an elevation mask less than 10. CORS stations are usually set around 5 but when processing you usually filter that by your 10 at the base on the ground. I use to set it to 90 so I couldn’t track anything as it was the quickest way to force a re initialization between measurements at times. As i was already in the screen to ck SN elevation etc. 0 would be bad news in my opinion as well. Unless someone was doing a study or research. But every day surveying no sir.
Set the base at 10, Rover at 15, if you get in timber or other clutter raise or lower the rover as needed. The elevation mask is really controlled at the rover. I suppose the base can be set at 0, I wouldn’t think that would be a good data collection procedure for later processing, but if all you’re doing is RTK, then it won’t matter.
