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Working RTK Base Station for less than $1,000
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Phainein7
Posted 6/5/2024 19:20 (#10764877 - in reply to #10764528)
Subject: RE: Working RTK Base Station for less than $1,000


Tipton, KS
golfnut - 6/5/2024  13:48

NTRIP RTK service


Yes, the base's location can be evaluated via RTK NTRIP provider, but not 100% perfect.  My X coordinate has always been off more than the Y coordinate via OPUS evaluations.  These values below represent a confidence interval rather than an actual offset. I did numerous OPUS evaluations, and this was the best result.
 
X: ± 11 mm, which is same as X: 0.011(m)
Y: ±  7 mm, which is same as  Y: 0.007(m)
Z: ±  4 mm, which is same as  Z: 0.004(m)

Even if a base station's coordinates are nailed perfectly, the equipment has its limitations.

Reach M2 spec
Static horizontal: 4 mm + 0.5 ppm

Reference Stations (CORS)
Static horizontal: 3 mm + 0.1 ppm

Your boards have horizontal specs, and IIRC, the first one was 8 mm horizontally.  Point: A base station's horizontal accuracy and its base coordinates affect a rover's pass to pass.  So, being 1/2" (13mm) off is close for pass to pass.  

In my setup, I must include the base's coordinates and the ellipsoidal elevation (not the ground elevation: Orthometric Elevation).  I don't know if ellipsoidal elevation affects XY coordinates, or is just for Z.  With an OPUS evaluation, the ellipsoidal elevation can be obtained.

>RTK NTRIP provider

I can't say how well these providers can model ionospheric activity, but when doing OPUS evaluations, this activity and where the satellites are located affect the result (precision).  How much, one test was within 3 feet, and after a number of evaluations, one result in the mm range (shown above).  GPS satellites used need to be at lower sky elevations for better precision.  Trimble has a webpage dedicated for sat orbits, etc (enter info, then change tabs at top): https://www.gnssplanning.com/#/settings

I have no idea where your NTRIP provider has reference stations, or if using the CORS at York, NE: https://geodesy.noaa.gov/cgi-cors/corsage.prl?site=NEYK  (NEYK) With current ionospheric activity, precision is not always possible.

Edited by Phainein7 6/5/2024 19:32




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