Short Baseline Test : Walking on NCTU Running Track 7 Laps
Test Environment
Test Result Using S2525F8-BD-RTK (GPS/Beidou RTK) : 16 ~ 21 combined GPS/Beidou signals above 15 degree elevation angle, 14 ~ 21 used for RTK. RTK Fix all the time during 7 laps.
http://navspark.mybigcommerce.com/content/20170504_S2525F8-BD-RTK_Test-NCTU.pdf
Test Result Using S2525F8-GL-RTK (GPS/GLONASS RTK, NS-HP-GL equivalent) : 12 ~ 17 combined GPS/GLONASS signals above 15 degree elevation angle, 7 ~ 15 used for RTK. Occasionally it became Float RTK in 4 out of 7 laps due to signal blockage and lower number of signal used; yet output position is still highly accurate as can be seen from the parallel track results. Test 2 on page-19 is done at corner seen from D location, having one side with nearby trees and buildings.
http://navspark.mybigcommerce.com/content/20170410_S2525F8-GL-RTK_Test-NCTU.pdf
A New 3rd Party $595 Dual Frequency RTK Receiver Open Field Test
It showed occasional Float RTK.
https://www.youtube.com/watch?v=dGpeIeRMnU4 (11:53 ~ 11:59, yell:RTK Fix, purple:Float RTK)
It being a GPS-only L1/L2C RTK receiver, with currently only 19 satellites having GPS L1/L2C capability in orbit, there is only 3 ~ 7 usable satellites above 15 degree elevation angle at any time.
For RTK initialization at least 5 satellites are required. When usable satellite number is low, there can be limited hours of RTK availability across 24hr period. If there are nearby trees or building further blocking signal, with insufficient usable signals RTK availability and reliability can be much affected.
Receiver Satellite Usage Situation Comparison
GPS L1/L2C satellites over US
GPS L1 + GLONASS L1 satellites over US
GPS L1 + Beidou B1 satellites over US
GPS L1/L2C satellites over Europe
GPS L1 + GLONASS L1 satellites over Europe
GPS L1 + Beidou B1 satellites over Europe
GPS L1/L2C satellites over Asia
GPS L1 + GLONASS L1 satellites over Asia
GPS L1 + Beidou B1 satellites over Asia
