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Alexander Chemeris alexander.chemeris at gmail.comHi Craig, On Tue, Apr 9, 2013 at 12:44 AM, Craig Reading <craig.reading1 at gmail.com> wrote: > PHew! - finally finished my experiments with RRLP. Full details at > www.genesysguru.com Your blog seems down - gives me 500/503 errors. > In summary: > > range error=ephemURA of xx.0 (xx) doesn't fit in (0,15) > > The problem seems to be that SV accuracy in metres is being used as the URA > index. The confusion arises due to differences between the Receiver > Independent Exchange Format (RINEX) 2.10 format and Interface Specification > IS-GPS-200 (http://www.gps.gov/technical/icwg/). IS-GPS-200 section > 20.3.3.3.1.3 states: ”SV Accuracy - Bits 13 through 16 of word three shall > give the URA index of the SV. The URA index (N) is an integer in the range > of 0 through 15.” > > RRLP server needs to be modified to support RINEX and specifically to add a > mapping from SV accuracy to URA index. For now I changed line 1084 in > rrlpserver.erl to assume a URA index of 6 e.g. SV accuracy in the range > 13.65 – 24 metres: > > stuff("ephemURA", nmth(7,1,Tokens), AdjustTable), > > Change to: > > stuff("ephemURA", “6” , AdjustTable), > > With Control.Call.QueryRRLP.Early OpenBTS option configured a crash occurs. > > OpenBTS: ../CommonLibs/Vector.h:189: void > Vector<T>::copyToSegment(Vector<T>&, size_t, size_t) const [with T = char, > size_t= unsigned int]: Assertion `base+span<=other.mEnd' failed. > > Hence the solution for now is to unconfigure this option: > > unconfig Control.Call.QueryRRLP.Early > > It looks at though the Almanac file downloaded from > http://www.navcen.uscg.gov/?pageName=currentAlmanac&format=yuma is saved > into /tmp/almanac as HTML rather than plain text: > > As a quick fix I changed my Almanac URL: > > config GSM.RRLP.ALMANAC.URL > http://celestrak.com/GPS/almanac/Yuma/almanac.yuma.txt > > My final configuration options are: > > config GSM.RRLP.ACCURACY 40 > config GSM.RRLP.ALMANAC.ASSIST.PRESENT 1 > config GSM.RRLP.ALMANAC.URL > http://celestrak.com/GPS/almanac/Yuma/almanac.yuma.txt > config GSM.RRLP.EPHEMERIS.ASSIST.COUNT 3 > config GSM.RRLP.EPHEMERIS.REFRESH.TIME 0.5 > config GSM.RRLP.RESPONSETIME 6 > > Hope this helps! Sounds great. Could you document this at the OpenBTS wiki? > I'm moving on to experiments with Uplink-Time Difference of Arrival (U-TDOA) > methods for locating mobile devices with a bit of GSM burst data analysis , > Complex Event Processing (CEP) and data correlation thrown in …. I call this > Mobile Fingerprinting … lets see! Looking forward to hear more about your results here - this sounds like an interesting area to explore. I see many applications where this would be useful. E.g. we're working with volunteering organization which search people in woods in Northern Russia - every year hundreds of people get lost. :( -- Regards, Alexander Chemeris. CEO, Fairwaves LLC / ООО УмРадио http://fairwaves.ru