# Lernkarten

Roland Schenkel
Karten 101 Karten 12 Lernende English Universität 17.01.2012 / 23.01.2021 Kein Urheberrechtsschutz (CC0)
0 Exakte Antworten 89 Text Antworten 12 Multiple Choice Antworten

Which terms are present in the observation equation of GPS?

receiver position at reception time, satellite position at emission time, tropospheric delay, ionospheric delay, relativistic correction, influence of multi-path, light travel time, light velocity

What is the meaning of the terms in equation (2.43)

re(tE): Receiver position at reception time (tE), rs(tS): =rs(tE-tES): Satellite position at the time of emission tS, trp: signal delay in troposphere, ion, signla delay in ionosphere, rel: relativistic correction, mul: infuence of multi-path

Differences between the phase and code observation equations

Vorzeichen für Ionosphären-Korrektur (pase advane, group delay), andere Wert für Multipath-Korrektur.

Why are often differences formed in GPS analyses (especially double-differences)?

to improve the accuracy: get rid of the satellite clock error, receiver clock error and other effects

Explain single Diff in GPS measurements?

2 Reveivers observe simultanous the same satellite // calculate the difference of the two observation equations // eliminated satellite clock error (it’s not totally eliminated - but nearly) // other errors are reduced as well, if baseline is not too long (sallite orbit errors, atmospherical and relativistic effects) // system noise increases by a factor of sqrt(2)

Explain double Diff in GPS measurements?

2 receivers, 2 satellites // differences of the observation eqations // eliminates receiver clock error (you still need to know the clock error to calculate the satellite positions in the correct epoch!) // system noise increases by a factor of 2

Explain tripple Diff in GPS measurements?

2 reveivers, 2 satellites measured in two epochs // eliminates the ambiguity // first robust solution for relativ-coordinates // system noise increases by a factor of 2*sqrt(2)

What type of instrumental effects have to be considered in GPS? What can be done to reduce their adverse effects?

a) multipath-effects b)phasecenter of GPS antenna: actual point of reception. Depending on azimuth and elevation of the GPS satellites. // 1) combining different antenna types: mainly affecting the height component (up to 10cm), horizontal position maximally a few millimeters if tropospheric zenith delays are estimated in the adjustment // 2) long baselines, errors even present if identical antenna types are used! due to different elevtion angle to the same satellite. //

ant(z,a) = -(r0e+(a,z)),

e = unit vector pointing from receiver to satellite,

Corrections are also necessary for the satellite antenna phase center!