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Jared: This question is a bit confusing to me as once the geometrically dispersed signals “collapse” on the antenna the length of the cable (each cable) manifests itself as a simple common mode time delay, so in this is fact not directly observable and more or less results in a small additional clock offset between the two independent receivers. Thus the delta length you mention of about 4.75 meters is just nSec lost (but tracked) between the two units. This is not a common RTK issue and is typically ignored (abs time people do care about it). And for what it is worth, pvs offsets and ARP values are typically in fractions of a cm and of the best value when merging/comparing L1 and L2 data, however uBlox does not have L2 data. If you are using a small patch antenna such as they supply then your effective phase center will vary by a meter or more depending on your own local ground plane and orientation, a non-trivial problem to overcome. I would bet your real issue is one of signal loss. I would suggest you confirm you are getting 40+ dB from both units and most signals as your first step. While uBlox is very sensitive, it needs a good signal to perform at its best. I presume in all this you are not trying to make this work in an indoor multipath ridden environment. A further simple way to validate your end to end chain with RTKLIB is to use the same antenna on both devices and confirm you are getting very rapid fixes with mm residual deviations. This also gives an insight into the residual tracking noise of both devices at once (aside the RINEX values will be similar but NOT be the same as again each has its own clock). A passive splitter, such as InStock #PD5120 for under $100 bucks (many other firm make a similar device) is a very useful item to have for this sort of testing with a common ant. Regards, David Kelley On 9/15/2014 7:29 AM, Jared Bench
wrote:
Does anyone know of a way to compensate for different antenna lengths between rover and base station? I |
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