Module 5

Question 1

GPS Nominal Constellation

Answer 1

• 24 satellites in 6 Orbital Plates
• 4 Stellites in each Plane
• 20,200 km altitudes
• 55 degree inclination

Question 2

Siderial Day

Answer 2

23h 56m 04s
Need to have a siberial day slightly shorter than a solar day, that shortness is 3 min and 56 sec per day
A siderial day is the bases of the gpa system, it is set up to make 2 orbits per siderial day,
so every day 2 orbits off set

Question 3

Sources of GPS Error

Answer 3

Standard positioning Service (SPS):

Selective Avaliability (1-100m) no longer a problem
Ionosphere (5-7m)
Troposphere (0.5-0.7m)
Satellite clocks (1 to 3.6 meters
Orbital errors (

Question 4

Basic Functions of GPS

Answer 4

• Positioning
• Distance and direction between your positon and a waypoint (computed vector)
• Velocity and travel log
• Time measurements

Question 5

Three Segment GPS

Answer 5

• Space segment
• Control segment
• User segment

Question 6

Control Segment

Answer 6

Master Control Station (US Space Command)

Monitor Station

Ground Antenna

Question 7

Pseudo Range R

Answer 7

Radius distance from satellite including clock bias.

lousy estimation of distance of satellite and location that includes clock error

Question 8

Ephemerous

Answer 8

• Ephemeris data describes short sections of satellite orbits
• A receiver gathers new ephemeris data each hour
• The ephemeris parameters are use to compute the SV position for any time within the period of the orbit described

short segments that tell unit where to expect satellite. frequency signal used to calculate Delta t (clock correction),what satellite is sending signal, location
(What orbit each satellite is), The trajectory for the next 4 hours
phase line loop

Question 9

Misclosure

Answer 9

error in benchmark (M)

Question 10

Misclosure Correction 2 ways:

Answer 10

-look at total horizontal distance (h), M*h/ perimeter
-break up error by number of segments (s) M/s
below elevation-add
above elevation-substract

Question 11

Why use one misclosure correction instead of the other?

Answer 11

• No making horizontal measurement

- long survay- mixture of short shots and long shots, then there are greater errors on long shots

Question 12

gps

Answer 12

• we can make elevation and horizontal position measurements
• access to satellite, sweeping away much of the old methodologies for surveying
• One instrument isolate allows you to make very precise measurement

Question 13

Autonomous gps

Answer 13

no ssistance from any other ground measurement (if we turn off WAAS)-

Question 14

Why gpa measurement from garmin worst for elevation than horizontal positioning?

Answer 14

A Hemisphere allows to make measurements of horizontal position with satellite around you. So if we had errors associated from one is offset by erros by another one to better locate horizontal
For vertical position we have satellite above our head to calculate error, but all in one direction there are not satellite below to balance your measurement. the one that fall below horizon are not available, only working working with half the satellite, half a view (180 degrees)

Question 15

First satellite

Answer 15

1979-in a decade period put in their orbit

Question 16

Do We want satellite set sun-earth frame that changes every day?

Answer 16

No, orbital plane are held on reference to distante start that are not changing to deal with the problem of the sun changing orientation to the satellites.

ex. between summer soltice and winter soltice, same time a day but reference has switch 180 degrees

Question 17

Orbital frame held static

Answer 17

earth turning, satellite moving but orbital frame remaining static.
For every satellite in view there is a green light going to black dot, when sattelite sits below horizon garmin cant pick it up (not available to you), turn in color red. Available on other side of world but not to you

Question 18

Selective availability

Answer 18

Before Bill clinton, high precestion only available to military, only degraded gps capability available until 1998 (100m measurement)
Unless US at war the whole constellation can be turn off in selective regions

Question 19

atmosphere (Ionosphere, Troposphere)

Answer 19

• Big sources of error are distortion in upper atmosphere

- Troposphere 1/10 of the error associate with ionosphere

Question 20

satellite clock

Answer 20

gps Clock from satellite, up to 3.6m error

Question 21

Orbit error

Answer 21

satellite position might be off

Question 22

Radio signal noise

Answer 22

call receiver noice

Question 23

Multipath

Answer 23

devise looking at constellation, trees…filter view to the sky, reflect/ bouncing signal off the ground that has a stronger signal than the received by the unit itself. There is sheilding

Question 24

Use gps for

velocity

Answer 24

stationary gps mounted permently concrete plataform can measure tectonic velocities-big uses of high precition gps units is to understant tectonic movement

Question 25

gps for time measurement

Answer 25

very precise time, for research, use gps to get highly precise time stamp for data log

Question 26

Monitor segment

Answer 26

24 gps satellites, and other that sit out waiting to be move into place if the other satellite go out or deorbital. Fly together only few meter apart.
Master station (Colorado) of from ground antennas transmitting info to satellite to move into orbit
US system 35 year old
US Space Command (colorado spring) satellite control in US airforce academy, they receive signal from monitoring station that tells that what each satellite is doing. every 4 hours send adjustment to get it into proper orbit

Question 27

Orbits do not cover

Answer 27

antartica or north artic. Big problems, degrade measurement there

Question 28

From way form Receiver can determine

Answer 28

how long is being since it left satelite (delta light), Times speed of light gives a range, cannot get position from one sattellite

Question 29

why we cannot get position from 3 satellites?

Answer 29

becasue they create 2 outcomes on either side where the spehre intersect, one positive and one negative
Need 4 satellite to know which of those two intersecting point is the real one

There is a unique situation where 3 satelitte could solve position, where they pecfectly intersect, without overlap. Right/place/time.

Question 30

clock bias

Answer 30

everys sattelite estimating the range using the same error. Need to factor out clock bias

ephemeral orbital
satelite correction-traveling small fraction in speed of light causing a shift on time, (relativety ) making things younger on saturday than earth by 14 sec
Relativety Needs to be factor in calculation of distances using gps

Question 31

Real? Range -

Answer 31

clock bias corrected range
clock error represented as distance error
Reference frame-WGS84

Question 32

Data frames
Satellite correction
Ephemeric data

Answer 32

for the next 4 hour, info about ionosphere, universal time, and generel map of all satellite

Question 33

GPS/GNSS

Answer 33

GPS
Nastar-gllobal satellite positioning
GPS-only refers to US system
GNSS- global navegation satellite system

Question 34

Galileo

Answer 34

operational on 2020.can take up Russian and US frequency

Question 35

PRN code

Answer 35

binary wave land, phase line loop use to align the wave form sent by satellite and recevied by receiver to determine delta T.
correltion coefficient of 1. One is perfectly aligned

Question 36

Time offset determination by phase-lock loop

Answer 36

Distance = c*t(offset)