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rtk starter KIT; why is it hard to get fixed


#1

Hi Lee

I try many times with your RTK Satrter Kit
sometimes it is normal ( easy to get fix), but mostly it is difficult to get FIX event with 12 SV detected
Am I missing something ?
I use NTRIP CLient android to get NTRIP Correction


#2

also… How can we know that it’s Switch B or Switch A mode ?
Could be the Switch mode make hard to FIX ?


#3

Follow the instruction in the User Guide for A/B switch position. If you don’t see Float RTK, only GPS or DGPS, then it’s push button mode setting and A/B switch position issue. If you see Float RTK but difficult to get RTK Fix, then it’s other issue. Make sure you have metallic plate underneath the antenna, it helps getting RTK Fix. 12 satellites is probably minimum, use GNSS Radar to choose time of day with more satellites if possible.

See if the posting at bottom of this thread helps understanding the issue: Performance degradation when not in RTK mode


#4

I achieve RTK fix less than 5% of the time.
What percent of the time should I be able to achieve RTK fix on any given day?
I would like to hear from others what percent of the time they are able to achieve RTK fix.

I am having a difficult time achieving RTK fix. What are the requirements? You mention 12 sats is minimum. Sometimes I have 16 sats and no RTK fix and sometimes I have 8 sats with RTK fix. It looks like I am nearly always short on number of sats with > 40dB or enough sats distributed throughout the four quadrants. I need almost 100% RTK fix for my application and would sacrifice some accuracy for that.

When looking at the number of sats available on any given day with https://www.gnssplanning.com/#/charts, it appears that the number of sats available is <= 12 sats a few times a day. This doesn’t account for available satellite spacial distribution among the quadrants. Does this mean I can only get RTK fix at very specific times of the day? This would not work for my application.

Is it possible that my survey grade antenna that I purchased is faulty?

Can I purchase one of your high performance antenna separately without an Alpha?

Is it possible that GPS/GLONASS sat constellations don’t work well with Alpha or the survey grade antenna? Maybe they weren’t tested as much as the other constellations?

Does a 10Hz update rate affect RTK fix?

Does the base station update rate need to be at 10Hz if the the rover is at 10 Hz?

Do any of the base station or server settings affect RTK fix?

Is a special firmware build with less stringent satellite requirements and having 6 cm accuracy possible?


#5

Hi Michael,

It looks like I am nearly always short on number of sats with > 40dB or enough sats distributed throughout the four quadrants.

Are we talking about RTK Base? Please do your best to locate your Base in an open field.

Is it possible that my survey grade antenna that I purchased is faulty?

Possible but in fairly rare cases.

Can I purchase one of your high performance antenna separately without an Alpha?

Yes here is the link to accessories and boards. Do you buy an antenna since you just wanna erase your last doubt?

Is it possible that GPS/GLONASS sat constellations don’t work well with Alpha or the survey grade antenna? Maybe they weren’t tested as much as the other constellations?

GPS constellations ought to work very well with Alpha especially in the homeland US.

Does a 10Hz update rate affect RTK fix?
Does the base station update rate need to be at 10Hz if the the rover is at 10 Hz?
Do any of the base station or server settings affect RTK fix?

The Base sends RTK correction data in 1Hz (please configure it to 1Hz, other value does not work) and the Rover can output NMEA data in 1/2/5/10 Hz.

Is a special firmware build with less stringent satellite requirements and having 6 cm accuracy possible?

RTK system is not likely to be modified that way.


#6

I really need to know if it’s practical to assume I can have RTK performance nearly 100% of the time on any given day with the base station on top of a building with no sky obstruction.


#7

Yes. That is what we see here.
You were correct: we need more satellites with receiving strength > 40 dB; those satellites help in RTK fix. Do you still have very small amount of satellites with strength >40dB?
For verification, please try to position your Base and Rover in the most open fields without air obstruction that you can find, even though the spots are not the ones you wanna position, and see if this helps RTK fix.