Mid day floatPosted by brad-ott on March 13, 2012 at 4:21 pm
Topcon Hiper+ local cell phone RTK setup is sweet, when it gets a fix.
However, typically from 10am to 2pm ish it just floats.
This seems to be true with both the private (PSC) and public (INCORS) networks.
For example, right now it says:
Common Sats 10
Initialized Sats 0
Position Type Float
What else can I try in order to get a fix?
No I do not have Glonass…
- 19 Replies
- MemberMarch 13, 2012 at 4:32 pm
Need a fix? Check out the scruffy-looking character killing time about a block from the high school.
- MemberMarch 13, 2012 at 4:35 pm
I always had mid-day trouble back in my Hiper days without Glonass. I think it’s a lack of satellites and if you have satalittes, where they are located, bad geometry. Now that I have a system that utilizes both GPS and Glonass I don’t have that problem. Pretty frustrating when you’re in the wide open and need to get some work done. You can always reboot, re-set base and rover and sometimes get a fix, but you’re better off keeping your RTK-ing, with that setup, to mornings and afternoons.
- MemberMarch 13, 2012 at 4:41 pm
Typical suggestions are Clear NVRAM on the receiver (hold FN key and power cycle unit, keep holding FN till Stat & Rec go from green to Amber/Red and start flashing), raise/lower mask angle (stick between 10 and 18 degrees, changing in 2 degree increments).
- MemberMarch 13, 2012 at 5:30 pm
There’s no reason to be floating during the day for that long even without GLONASS. With a 10 degree mask, only drops to 6 satellites once during a 12 hour period. Most of the times, it’s at 8 or more. PDOP < 3 the entire day.Call Topcon tech support. There’s a bug somewhere in your system.> Topcon Hiper+ local cell phone RTK setup is sweet, when it gets a fix.
> However, typically from 10am to 2pm ish it just floats.
> This seems to be true with both the private (PSC) and public (INCORS) networks.
> For example, right now it says:
> Common Sats 10
> Initialized Sats 0
> Position Type Float
> What else can I try in order to get a fix?
> No I do not have Glonass…
- MemberMarch 13, 2012 at 5:32 pm
Have you tried a static location at the same time?
Your issue is the lack of initialization which could mean that there is a communication issue. I’ve never used the cell modems, so I have to wonder if there is some reason the signal is being affected mid-day. Do you have UHF/SpreadSpectrum Radio abilities and have you tried using your own base station?
- MemberMarch 13, 2012 at 5:53 pm
Is the accuracy different between float and fix?
- MemberMarch 13, 2012 at 6:28 pm
> Is the accuracy different between float and fix?
- MemberMarch 13, 2012 at 7:14 pm
Bandwidth at cell tower is overloaded, probably kid at lunch time.:-(
- MemberMarch 13, 2012 at 7:33 pm
> Need a fix? Check out the scruffy-looking character killing time about a block from the high school.
:-/ that did give me a grin, … after I got my fix (pbr ?)
- MemberMarch 13, 2012 at 8:06 pm
The info that needs to be transmitted between a base and a rover has a limited time to get there. After that the next packet of info is coming and if the first packet hasn’t got there then it gets overridden. Sometimes there is too much data and the system gets overloaded. This will become more prelevant as radios get narrowbanded. The narrowbanding will restrict how much data can be sent at one time. You may need to turn off satellites or up the elevation mask to reduce how many are available.
If you can I would try and run a test between the cell phone system and a RTK radio system. This might tell you that the cell phone system is just not getting the data through in time (not enough bandwidth).
There are also other reasons like cleaning out old data from your rover.
- MemberMarch 13, 2012 at 8:14 pm
float = +/- meters
fixed = +/- centimeters
- MemberMarch 13, 2012 at 9:28 pm
When did you last upgrade your firmware?
I thought we were gonna get some pics of you in a canoe!
- MemberMarch 14, 2012 at 4:00 am
that isn’t exactly an accurate statement
- MemberMarch 14, 2012 at 4:21 am
yeah, i was just generalizing. close enough to know where these terms fit into the scheme.
too many unknowns to make a better error estimate
- MemberMarch 14, 2012 at 4:29 am
Float can be more accurate than fixed. Those two terms are a little more than placebo. Float is often within tenths and fixed is sometimes out a couple of meters though I agree that fixed is normally better.
- MemberMarch 14, 2012 at 4:52 am
Mission planning. Just cuz there are enough satellites doesn’t mean there is good geometry.
- MemberMarch 14, 2012 at 10:29 am
did you check what the sun was doing?
I have been having ‘some issues’ with my RTK setup and had a ‘check’ day yesterday (13th March) to see what I could salvage from 2 previous attempts at RTK cadastral control.
It would not fix at all for me yesterday, but I did have a rather dubious base battery that I changed for a nearby farmers rideon battery. Didn’t give me a fix though.
I see the solar muscles have been flexing recently so haven’t discounted their effect.
- MemberMarch 14, 2012 at 12:28 pm
Sun has been very active 2 last weeks, this may have an affect. Check here for current state in the top right corner.
http://www.ngs.noaa.gov/PUBS_LIB/NGSRealTimeUserGuidelines.v1.1.pdf pdf page 30. (paper page 24)
- MemberMarch 14, 2012 at 5:18 pm
Agreed. Another thing Brad might want to figure out is if high cellular link to the CORS tower or network is working correctly. Can he verify he is actually receiving correction messages? And is he receiving them regularly without interruptions?
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