1

WORKSHOP PLAN

ROCKET SCIENCE

HISTORY OF GPS DEVELOPMENT

COMPONENTS OF THE GPS SYSTEM

HOW GPS GIVES US POSITIONS

METHODS & APPLICATIONS

GPS GROWTH

(Source: University of Washington Olympic Natural Resources Center.)

2000 1.5 MILLION USERS ECONOMIC IMPACT = $6.2 BILLION

2010 1 BILLION USERS 1 BILLION RECEIVERS ECONOMIC IMPACT = $50 BILLION

2

LINK TO SLIDES:

ftp://ftp.ngs.noaa.gov/dist/whenning/njspls2012/

EVERY EPOCH OF OBSERVATION MUST COMPUTE CHANGE IN POSITION DUE TO EARTH ROTATION, SATELLITE ORBIT CHANGE AND RELATIVITY!

AT “C”, 1 NANOSECOND = 30 CM!

3

900+/- OPERATIONAL SATELLITES- HALF COMMERCIAL, MOST “LEO”& POLAR ORBIT-HUNDREDS OF THOUSANDS

OF PIECES OF SPACE DEBRIS

JUNK IN SPACE A SHORT HISTORY of GPS DEVELOPMENT

• 1956 – Friedwart Winterberg (theoretical physicist at U of NV) proposed test of general relativity using atomic clocks in satellites

• 1958 – Two American Physicists: William Guier & George Weiffenbach (JHAPL), monitor Sputnik using Doppler effect principles of its radio signal to compute its orbit using UNIVAC II, leading to the development of the Navy TRANSIT system 1964-1996(using the reverse solution).

• 1960 – First Navy TRANSIT satellite launched. System of 5 satellites with 1 fix/hour.

• 1963 – Air Force “Project 57” 3-D LORAN-like system study births the GPS concept.

• 1967 – Navy places atomic clocks in space

• Cold war arms race drives research using billions of dollars for precise navigation for: submarine ballistic missiles, strategic bombers, and ICBMs.

4

HOW DID GPS EVOLVE? • PRECURSORS:LORAN (WWII at MIT), 1200 mile range

DECCA NAVIGATOR (1940’S), 400 mile range)

RADIO TRANSMITTER AT A KNOWN POSITION

RADIO TRANSMITTER AT A KNOWN POSITION

The phase difference between the time of reception of synchronized signals from stations A and B is constant along each LINE OF POSITION

RECEIVER

Master station frequency

Slave station harmonic frequency and/or pulse delay

LINES OF TIME DIFFERENCE CAN DETERMINE POSITION

SYNCHRONIZED SIGNALS

• Labor day Weekend, 1973 – 12 military officers meet at the Pentagon & create the “Defense Navigation Satellite System” (DNSS)- renamed NAVSTAR.

• 1978 – First experimental Block I GPS satellite launched

• 1983 – President Reagan issues directive to make GPS freely available for public use, after Korean flight 007 shot down over Russian airspace.

• 1985 – GPS command & control center moved to 2nd Satellite Control Squadron at Falcon AF Station in Colorado Springs (now “Schriever”). 10 Block I satellites in orbit.

• February 14, 1989 – First Block II satellite launched

• 1990-1 – Gulf war is first conflict where GPS is used.

• 1993 – 24 satellites in orbit

• April 1995 – Full operational capability declared by Air Force Space Command.

A SHORT HISTORY of GPS DEVELOPMENT

5

• 1996 – GPS declared a dual use (military and civil) system by President Clinton

• Midnight May 1, 2000 - Degraded civilian signal (Selective Availability) ordered turned of at by President Clinton.

• 2004 – President Bush establishes National Executive Committee on Space Based Position Navigation and Timing(PNT)

• 2005 – First modernized GPS satellite IIR-M1 launched with L2C signal.

• April, 2010 – GPS satellite IIR-20M locks third frequency allocation with first L5 broadcast.

• Oldest operational GPS satellite is 21 years old (stated expected life was 7 years).

A SHORT HISTORY of GPS DEVELOPMENT GLOBAL POSITIONING SYSTEM- Operated by

NAVSTAR GPS Joint Program Office at the Space and Missile Systems Center, Los Angeles

Air Force Base, California.

NAVIGATION, SATELLITE TIMING AND RANGING

Ivan Getting (Aerospace Corp.), Roger Easton (NRL), & Brad Parkinson (Stanford)- three giants of GPS development 1960‟s-1970‟s.

EST. 2005, REPLACING IGEB

6

GPS GROUND CONTROL SEGMENT

GROUND CONTROL SEGMENT

Source: http://www.navcen.uscg.gov/cgsic/meetings/summaryrpts/

FUNCTIONS OF THE GROUND SEGMENT

Diagram Source: GPS System Segments Arthur J. Dorsey and Willard A. Marquis Lockheed Martin Corporation Peter M. Fyfe The Boeing Company Elliott D. Kaplan and Lawrence F. Wiederholt The MITRE Corporation

Satellite-tracking-station on Hawaii (Source: Schriever Air Force Base Satellite Flyer Vol. 6; No.12)

7

ORBITAL ERRORS CONTRIBUTING TO PPM ERRORS

(See user guidelines references for Graphic: Ahn, 2005)

2-5 m

1 cm! (2005+)

GPS SPACE SEGMENT

GPS III-A

LAUNCH HISTORY

8

GPS ORBITAL PLANES & SLOTS GPS SIGNALS

2010

9

GPS SIGNALS- CODE PHASE

36 suitable codes are referred to as GOLD-codes (names after a mathematician). For these GOLD-codes the correlation among each other is particularly weak, making an unequivocal identification possible.

Navigation Data–50Hz Data, –Satellite Almanac, –Satellite Ephemeris,–Satellite Clock Error –GPS Time to UTC–Ionosphere Model parameters–User Range Accuracy(URA)

CODE MODULATES THE CARRIER WAVE PHASE MODULATION:

When a data signal shall be modulated onto a carrier signal by phase

modulation, the sine oscillation of the carrier signal is interrupted and restarted

with a PHASE SHIFT OF 180°. This phase shift can be recognized by a suitable

receiver and the data can be restored. Phase modulation leads to an extension

of the frequency range of the carrier signal (leading to a spread spectrum)

depending on how often the phase is shifted. When the phase changes, wave

peaks are followed by wave minimums in a shorter distance than were in the

original carrier signal (as can be seen in the graph).

This kind of modulation can only be used for the transmission of digital data.

SOURCE:http://www.kowoma.de/en/gps/signals.htm

GPS SIGNAL STRUCTURE

10

PRN CODE MODULATION THE “BEAT” PHASE- DIFFERENCING THE DOPPLER RECEIVED

SIGNAL WITH THE RECEIVER GENERATED SIGNAL

The beat frequency is equal to the absolute value of the difference in

frequency of the two waves. Therefore, the original carrier frequency and

wavelength can be extracted

GPS NAVIGATION MESSAGE

Each 30 second frame begins precisely on the minute or half minute as indicated by the atomic clock on each satellite. The first part encodes the week number and the time within the week, as well as the health of the satellite. The second part of the message, the ephemeris. The last part of the message, the almanac, contains coarse orbit and status information for all satellites in the network as well as data related to error correction. Signals are encoded using code division multiple access (CDMA) allowing messages from individual satellites to be distinguished from each other based on unique encodings for each satellite (that the receiver must be aware of). Two distinct types of CDMA encodings are used: the coarse/acquisition (C/A or civil) code, and the precise (P) code, that is encrypted so that only the U.S. military can access it. The ephemeris is updated every 2 hours and is generally valid for 4 hours. The almanac is updated typically every 24 hours.

11

GPS NAVIGATION MESSAGE

MAY 2010

12

NEW SIGNALS BOTTOM LINE: L5 (1176.45 MHz) , L2C (NEW CIVIL CODE)

• More robust •Faster AR • Stronger signal - lower carrier-to-noise-density ratio (c/n0) values than would otherwise be possible. • Better signal tracking & differentiation especially at lower elevations means better code positioning under canopy (the better cross-correlation performance means that the reception of weak gps signals is much less affected by simultaneously received strong gps signals, which can be of significant advantage in difficult signal reception conditions.) •Code iono error mitigation using L1 C/A, L2C, & P2 differencing (eventually L5 on block IIF & L1C on block III) •Longer baseline solutions •improved QA/QC with additional frequency checking •Faster, more accurate NAV updates • L2C has similar multipath characteristics as L1 C/A

“TIME”- WHAT DOES GPS USE? TAI / UT1 TIME

International Atomic Time (TAI) as a time scale is a weighted average of the time kept by over 200 atomic clocks in about 70 national laboratories worldwide based on VLBI measurements

UT1 is the principal form of Universal Time. While conceptually it is mean solar time at 0° longitude, precise measurements of the Sun are difficult. Hence, it is computed from observations of distant quasars using long baseline interferometry, laser ranging of the Moon and artificial satellites, as well as the determination of GPS satellite orbits. UT1 is the same everywhere on Earth, and is proportional to the rotation angle of the Earth with respect to distant quasars, specifically, the International Celestial Reference Frame (ICRF)

UT1 IS ATOMIC TIME KEPT RELATIVE TO THE MEAN SOLAR DAY ≈ 24 HOURS USING THE QUASARS

POSITION EVERY ROTATION ≈ 23h 56 m

13

As of 1 January 2011 (2011 -01-01), 00:00:00 UTC, TAI was exactly 34 seconds ahead of UTC (this is the case since 1 January 2009): an initial difference of 10 seconds at the start of 1972, plus 24 leap seconds in UTC since 1972; the last leap second was added on 31 December 2008

“TIME”- WHAT DOES GPS USE? UTC TIME

Because Universal Time (UTC)is synchronous with night and day, and more precise atomic-frequency standards drift away from this, UT is still used to produce a correction (called a leap second) to atomic time, in order to obtain a broadcast form of civil time that carries atomic frequency. Thus, civil broadcast standards for time and frequency usually follow TAI closely, but occasionally change discontinuously (or "leap") in order to prevent them from drifting too far from mean solar time (UT1).

UTC IS ATOMIC TIME KEPT RELATIVE TO UT1 USING LEAP SECONDS. IT IS OUR CIVIL TIME BASIS

24 H

While most clocks are synchronized to Coordinated Universal Time (UTC), the atomic clocks on the satellites are set to GPS time (GPST): The difference is that GPS time is not corrected to match the rotation of the Earth, so it does not contain leap seconds or other corrections that are periodically added to UTC. GPS time was set to match Coordinated Universal Time (UTC) JAN 1, 1980, but has since diverged. The lack of corrections means that GPS time remains at a constant offset with International Atomic Time (TAI) (TAI – GPS = 19 seconds). Periodic corrections are performed on the on-board clocks to keep them synchronized with ground clocks

“TIME”- WHAT DOES GPS USE? GPST TIME

GPST IS ATOMIC TIME KEPT RELATIVE TO TAI STARTING 1/1/1980

GPS TIME

ORIGIN = JANUARY 1, 1980, ATOMIC TIME DELAYED 19 SECONDS TO TAI AT ORIGIN (CONSTANT) UTC IS CURRENTLY DELAYED 15 SECONDS TO GPS TIME TIME OF WEEK IN SECONDS FROM SUNDAY MORNING THROUGH SATURDAY NIGHT = 604799 SECONDS GPS PASSED THROUGH ITS 1 BILLIONTH SECOND SEPTEMBER 14TH (2011). PROCESSING PROBLEMS? GPS WEEK ROLLOVER: 8/15/99 = WEEK 1022 8/22/99 = WEEK 0 9/18/11 = WEEK 630 (1654)

14

http://www.rvdi.com/freebies/gpscalendar.html

http://adn.agi.com/GNSSWeb/

“JULIAN DAY NUMBER” IS TERRESTRIAL TIME SINCE JAN.1, 4713 B.C. AT NOON

“GNSS”

GLONASS

GPS

GALILEO

COMPASS (BEIDOU-2)

GPS USERS SEGMENT

•SURVEYING/ENGINEERING, BUT SOME OTHER VERY IMPORTANT APPS: •CELLULAR NETWORKS •BANKING- $$ TRANSFERS/ATMS •POWER GRIDS •TRANSPORTATION- SHIPS/RAIL/TRUCKS •EMERGENCY MANAGEMENT •WEATHER PREDICTION •DEFORMATION MODELING •CRUSTAL MOTION & OTHER SCIENTIFIC APPS •“GRACE” POITIONS FOR HIGH DEF. GRAVITY= NEW GEOPOTENTIAL DATUM FOR US!

15

EXPANDING GPS MARKETS

GIS INFRASTRUCTURE

MOBILE MAPPING SYSTEMS

MACHINE GUIDANCE

BETTER THAN “COUPLA” METERS

16

WHAT DATA DOES GPS NATIVELY GIVE ME?

NAD 83? NAVD 88?

LATITUDE, LONGITUDE?

-

Z

Y X

-Z

-X

-Y

Zero

Meridian

Mean Equatorial Plane

GNSS POSITIONS ARE ECEF, XYZ

ALL GPS SATELLITES‟

POSITIONS ARE MAINTAINED IN

ECEF X,Y,Z (WGS 84 DATUM)

Earth-Centered-Earth-Fixed Coordinates

Z Axis

X Axis

Y Axis

(X,Y,Z)

Earth’s

Surface

Zero

Meridian

Mean Equatorial Plane

P

Origin

(0,0,0)

Center of Mass

X

Y

Z

Conventional

Terrestrial

Pole

17

X,Y,Z TO ,,h

Z Axis

X Axis

Y Axis

(X,Y,Z) = P (,,h)

h

Earth’s

Surface

Zero

Meridian

Mean Equatorial Plane

Reference Ellipsoid

P

ELLIPSOID, GEOID & ORTHO HEIGHTS

H88 = h83 – N09

WHAT DOES THE NGS DO?

• DEFINES AND MAINTAINS THE NATIONAL COORDINATE SYSTEMS – NAD 83, NAVD 88 – CORS, HPGN/HARN/FBN/CBN – MODELS TO TRANSFORM AND DESCRIBE

CHANGES.

• DEVELOPS FEDERAL STANDARDS AND GUIDELINES AND COORDINATES SURVEY WORK.

• DETERMINES THE NATIONAL SHORELINE – DEFINES TERRITORIAL LIMITS, BASELINE FOR

MANAGEMENT OF COASTAL RESOURCES

• PERFORMS AERONAUTICAL SURVEYS – OBSTRUCTIONS CHARTS, AIDS TO NAVIGATION,

AND ACCURATE AIRPORT SURFACE MAPS

18

NGS DTASHEET- E 167

E-167 FUTURE NGS DATASHEET

• POSITIONAL ACCURACIES: “NETWORK” (TO THE DATUM) AND “LOCAL” (TO THE PROJECT NEIGHBORS)

• ORTHOMETRIC HEIGHTS LEVELED OR TO 2 CM FROM ELLIPSOID + GRAVIMETRIC GEOID

• VELOCITIES GIVEN FOR N,E & UP. WILL THE NEW DATUM BE FIXED TO THE N.A. PLATE?

• ACCESS TO THE NATIONAL DATUMS (NSRS)ARE FROM ACTIVE CORS NETWORK ONLY. SECONDARY ACCESS TO PASSIVE MARKS USED BY CAVEAT EMPTOR.

• ALIGNMENT TO LEGACY DATA, SUCH AS LOCAL PROJECTS, FROM SITE CONSTRAINTS

19

JANUARY 2012 NGS

DATASHEET

20

GNSS TO ANY DATUM

• GNSS ECEF X,Y,Z (WGS 84 & PZ90)

NAD 83 (,,h) SPC N,E,h

+ GEOID XX = SPC N,E,H

OR

“CALIBRATE “ TO 4-5 SITE POINTS IN THE DESIRED DATUM. THIS IS USED TO LOCK TO PASSIVE MONUMENTATION IN THE PROJECT

AREA.

EXAMPLE: GPS TO SPC + ELEVATION:

CONSTRAINING PASSIVE MARKS

GLONASS- FULL OPERATIONAL CAPABILITY 2011 EUROPEAN UNION - GALILEO CHINA – COMPASS/BEIDOU REGIONAL: (JAPAN- QZSS FIRST LAUNCH 2010) (INDIA – GAGAN)

CHANGES IN GNSS

GPS: • L2C • L5 CARRIER • New Code on L5 • L1C 1-3 m

BETTER RESISTANCE TO INTERFERENCE

FASTER AMBIGUITY RESOLUTION

AUGMENTED CODE APPLICATIONS

= 115 SATELLITES?

10-15 cm???

21

GALILEO- OFF THE GROUND OCTOBER 21, 2011

2 IOV SATELLITES, EUROPEAN SPACEPORT, FRENCH GUIANA, RUSSIAN SOYEZ ROCKET (SPUTNIK, YURI GREGARIN)

GLONASS STATUS

NEW SIGNALS BOTTOM LINE: L5 (1176.45 MHz) , L2C (NEW CIVIL CODE)

• More robust • Stronger signal - lower carrier-to-noise-density ratio (c/n0) values than would otherwise be possible. • Better signal tracking & differentiation especially at lower elevations means better code positioning under canopy (the better cross-correlation performance means that the reception of weak GPS signals is much less affected by simultaneously received strong gps signals, which can be of significant advantage in difficult signal reception conditions.) •Code iono error mitigation using L1 C/A, L2C, & P2 differencing (eventually L5 on block IIF & L1C on block III) •Longer baseline solutions •Faster ambiguity resolution •improved QA/QC with additional frequency checking •Faster, more accurate NAV updates • L2C has similar multipath characteristics as L1 C/A

22

IN TEN YEARS……. • 115+ SATELLITES • 1.5 DM AUTONOMOUS POSITIONING • NEW GEOMETRICAL DATUM – ITRF ALIGNED GEOCENTER BUT PROBABLY FIXED ON NORTH AMERICAN PLATE. NSRS ENTIRELY REALIZED BY ACTIVE STATIONS OF THE FOUNDATION CORS • NEW NATIONAL GEOPOTENTIAL DATUM – 1 CM GRAVIMETRIC GEOID, ORTHOMETRIC HEIGHT SITE CONTROL TO 2 CM RELATIVE TO THE NATIONAL DATUM. • MORE REMOTE SENSING: 2 - 3 DM SATELLITE IMAGERY/MAPPING , MMS • INDOOR AND UNDERGROUND POSITIONING

• Active sites

1850+

• 1250 used

in NAD

83(2011)

CORS Network

continued growth

RTN AND NGS “FOUNDATION CORS” WILL BE THE PRIMARY ACCESS TO THE NSRS

Disturbed Geodetic Control

Coordinates/Elevations

Questionable!

Destroyed Geodetic Control

No Coordinates/Elevation

Monumented Points

Deterioration

MISSING MARKS- TYPICAL EXAMPLE

23

MISSING MARKS- TYPICAL EXAMPLE PASSIVE MARKS VS. ACTIVE STATIONS CONUNDRUM

1,500,000 MARKS IN THE NGSIDB 1850 NATIONAL CORS 107 RTN OPUS/CORS POINT (SOON PROJECT) PROCESSING PASSIVE MARKS GET DISTURBED, DESTROYED, AND CAN BE HARD TO RECOVER EVERYTHING MOVES, BUT WE KNOW WHERE THE ANTENNAS ARE 24/7/365.25 GNSS POSITIONING IS GETTING MORE AND MORE PRECISE GNSS POSITIONING CAN EASILY USE OUR NATIONAL DATUMS, MAKING GIS FIT TOGETHER AND YIELDING HOMOGENEOUS DATA

AUGUST 23, 2011 MAGNITUDE 5.8 EARTHQUAKE DAMAGE- WHAT ABOUT MARKS IN THE GROUND?

24

Height

Modernization

-faster

-cheaper

-Nearly as good

differential leveling

GNSS

HEIGHT MODERNIZATION- BACKGROUND

CHA – CHING $$$$$$$ ♪♪♪ Heights Matter!

TYPICAL GNSS EQUIPMENT

• STATIC: ALL: FIXED HEIGHT TRIPOD, DUAL FREQUENCY GPS RECEIVER (MAY HAVE GLONASS), GEODETIC ANTENNA, EXTERNAL OR INTERNAL BATTERIES, CELL PHONE, OBSERVATION SCHEDULE, MAP BOOK, LOG BOOK, VEHICLE.

25

TYPICAL GNSS EQUIPMENT • REAL TIME:BASE: FIXED HEIGHT TRIPOD, DUAL FREQUENCY

GPS RECEIVER (MAY HAVE GLONASS), GEODETIC ANTENNA, EXTERNAL BATTERIES, UHF RADIO GEAR OR DATA MODEM. ROVER: RECEIVER/ANTENNA INTEGRATED UNIT, CARBON FIBER POLE, DATA COLLECTOR, INTERNAL UHF RADIO (RECEIVE) OR DATA MODEM

SINGLE BASE ONLY BOTH SINGLE BASE & RTN

POSITIONS FROM GNSS OBSERVATIONS

• STATIC POST PROCESSING- USING PASSIVE MARKS

• STATIC ACTIVE STATION POST PROCESSING (CORS DATA)

• STATIC NGS POST PROCESSING (OPUS)

• REAL TIME – YOUR BASE

• REAL TIME – NETWORK SUPPLIED

• AUTONOMOUS

OPUS - S • DUAL FREQUENCY DATA

• ≥ 2, ≤48 HOURS DATA

• PAGES ENGINE

• OBS USED > 90%

• # FIXED AMB > 50%

• OVERALL RMS < 3 cm

• PEAK TO PEAK < 5 cm

OPUS - RS • DUAL FREQUENCY DATA

• ≥ 15 MINUTES, ≤2 HOURS DATA

• RSGPS ENGINE

• ≥ 3, ≤ 9 CORS, 250 KM

• OBS USED > 50%

• QUALITY INDICATOR ≥ 3

• NORMALIZED RESIDUAL ≈ 1

• OBS USED ≥ 70%

• # FIXED AMB ≥ 70%

• OVERALL RMS ≤ 3 cm

• PEAK TO PEAK ≤ 4 cm

• DESCRIPTION

• PICTURES

OPUS - DB

BLUEBOOKING

26

SIMPLE IS BETTER!

A comparison: Files used:

(create, sort, maintain)

Required Metadata

(input)

Programs used:

(learn, run, maintain)

BLUEBOOK

16 files xxxxxxxxxxx

xxxxx

378 elements xxxxxxxxxxx

xxxxxxxxxxx

xxxxxxxxxxx

xxxxx

26 programs xxxxxxxxxxxxx

xxxxxxxxxxxxx

OPUS-DB 2 files

xx

(GPS data + photo)

15 elements xx

1 program x

(internet browser)

WHAT CAN I EXPECT FROM STATIC GNSS POSITIONING?

NETWORK CAMPAIGNS: = SUB-CENTIMETER GEOMETRICAL WITHIN NETWORK, 2 CENTIMETER ORTHOMETRIC HEIGHTS SINGLE POSITION: (CORS/OPUS) ≈ 1 CENTIMETER TO NSRS GEOMETRICAL WITH ≥ 4 HOURS, ≈ 5 CENTIMETERS ORTHOMETRIC HEIGHT

WHAT CAN I EXPECT FROM REAL TIME POSITIONING?

REAL TIME NETWORKS (RTN): A “FEW” CENTIMETERS. GEOMETRICAL. MOST RTN PRODUCE “GOOD” HORIZONTAL VALUES. OUR HORIZONTAL SYSTEM IS BASED ON ACTIVE REFERENCE STATIONS (NGS CORS), AS ARE THE RTN STATIONS. 7 OR 8 CENTIMETERS ORTHOMETRIC HEIGHT. BECAUSE ORTHOMETRIC HEIGHTS („ELEVATIONS‟) ARE BASED ON PASSIVE MONUMENTS, THE RTN USER SHOULD, FOR THE MOST PART, CONSTRAIN THE PASSIVE MARK VALUES IN A LOCALIZATION. SINGLE BASE: 2 CENTIMETERS REPEATABLE GEOMETRIC & ORTHOMETRIC HEIGHT TO A LOCAL BASE POSITION LESS THAN 10 K DISTANT. HOW DOES THAT BASE RELATE TO THE TRUTH?

27

WHY DOES MY CAR GPS GIVE ME ERRORS?

• Datum

• Accuracy

• Grid/ground

• INS Degradation

• Map errors

PRECISION VS. ACCURACY

•“PRECISION” IS A COMPUTED STATISTICAL QUANTITY TO THE SOURCE OF THE MEASUREMENT - ALIGNMENT TO THE RTN OR PASSIVE MARK SHOWS PRECISION OF THE OBSERVATION (PER THE DATA COLLECTOR). •“ACCURACY” IS A COMPUTED STATISTICAL QUANTITY TO THE REALIZATION OF THE DATUM - ALIGNMENT OF THE RTN OR PASSIVE MARK TO THE NSRS SHOWS ACCURACY (PER ESTABLISHED METHODOLGY) •

PRECISION vs. ACCURACY

PRECISE – NOT ACCURATE

ACCURATE AND PRECISE

ACCURATE – NOT PRECISE

28

GPS USERS SEGMENT

GPS SIGNALS- CARRIER PHASE

THE INTEGER AMBIGUITY

D = First Partial Wavelength

N = Integer Ambiguity

Resolving the integer ambiguity allows phase

measurements to be related to distances

Distance = N + D

WGS 84

X,Y,Z L1 & L2 CARRIER PHASE

L1 = 1575.42 MHz = 154 x 10.23 MHz L2 =1227.6 MHz = 120 x 10.23 MHz And L5 = 1176.45 MHz = 115 x 10.23 MHz The wavelengths of the carriers are: λ1 = 19.03 cm λ2 = 24.42 cm λ5 = 25.48 cm

29

WHY DOES GPS USE CERTAIN FREQUENCIES?

Choice of the carrier frequency: To transport data signals, a suitable carrier frequency is required. -Frequencies should be chosen below 2 GHz, as frequencies above 2 GHz would require beam antennae for the signal reception -Ionospheric delays are enormous for frequency rages below 100 MHz and above 10 GHz -The speed of propagation of electromagnetic waves in media like air deviates from the speed of light (in vacuum) the more, the lower the frequency is. For low frequencies the runtime is falsified. -The PRN-codes require a high bandwidth for the code modulation on the carrier frequency. Therefore a range of high frequencies with the possibility of a high bandwidth has to be chosen. The chosen frequency should be in a range where the signal propagation is not influenced by weather phenomena like, rain, snow or clouds.

SOURCE:http://www.kowoma.de/en/gps/signals.htm

The ambiguity is an integer number (a multiple of the carrier wavelength).

The integer is different for the L1 and L2 phase observations.

The integer ambiguity is different for each satellite-receiver pair.

The integer ambiguity is a constant for a particular satellite-receiver pair for

all epochs of continuous tracking (that is, as long as no cycle slips occur)

The carrier phase measurement from one observation epoch to another is

a measure of the change in satellite-receiver range.

The determination of the cycle ambiguity integer is known as ambiguity

resolution, and is generally not an easy task because of the presence of

other biases and errors in the carrier phase measurement.

THE AMBIGUITY SEARCH…. SOME REAL TIME INTEGER FIXING TECHNIQUES- DUAL FREQUENCY ALSO ENABLES OTF INITIALIZATION

• Wide Laning (L1 – L2) = c (speed of light) ÷ (1575.42 MHz – 1227.60 MHz) or 299,792.458 Km/sec ÷ 347.82 MHz = 0.862 m wave length. [L5-L1 = 75CM]

• Narrow Laning (L1 + L2) = c (speed of light) ÷ (1575.42 MHz + 1227.60

MHz) or 299,792.458 Km/sec ÷ 2803.02 MHz = 0.107 m wave length

• Iono Free f(L1)ion-free = a1.f(L1) + a2.f(L2)

with a1 = f12/(f1

2 - f22 ) and a2 = - f1 . f2 /(f1

2 - f22 )

• Triple Differencing

• Kalman Filtering

• Double Differencing

30

INTEGER SEARCH WHAT CAN AFFECT THE GPS SIGNAL?

WHAT SHOULD I BE CONCERNED ABOUT WHEN COLLECTING DATA?

31

IONO & TROPO LAYERS AND THEIR EFFECT ON THE GNSS SIGNAL

TROPOSPHERE DELAY

The more air molecules, the slower the signal (dry delay)

High pressure, Low temperature

90% of total delay

relatively constant and EASY TO CORRECT FOR

The more water vapor in the atmosphere the slower the signal (wet delay)

High humidity

10% of total delay

Highly variable and HARD TO CORRECT FOR

IONOSPHERIC EFFECTS ON POSITIONING

HIGH IONO- NO NETWORK

AVERAGE IONO- NO NETWORK

WITH NETWORK

(SOURCE-BKG- GERMANY)

DISTANCE TO REFERENCE STATION (KM)

2D

PR

EC

IS

IO

N/A

CC

UR

AC

Y (

CM

)

SINGLE BASE

RTK @ 10 KM

NETWORK SOLUTION

@ 30 KM

(1994-1995) (2000-2002)

32

IONO, TROPO, ORBIT CONTRIBUTE TO PPM ERROR

REMEMBER GNSS EQUIPMENT MANUFACTURERS‟ SPECS!

WWW.SWPC.NOAA.GOV SUNSPOT CYCLE

• Sunspots follow a regular 11 year cycle

• We are just past the low

point of the current cycle

• Sunspots increase the radiation hitting the earth's upper atmosphere and

produce an active and unstable ionosphere

2013

http://www.swpc.noaa.gov/

33

Thank you for using the Product Subscription Service. If you would like to

remove a product subscription or update the personal information in your

account, go to the Product Subscription Site. Please do not use the from

address for correspondence, as it is not monitored. For comments or help,

please contact SWPC Help.

Space Weather Message Code: ALTK07 Serial Number: 83 Issue Time:

2011 Aug 05 2328 UTC ALERT: Geomagnetic K-index of 7 Threshold

Reached: 2011 Aug 05 2328 UTC Synoptic Period: 2100-2400 UTC

Station: Boulder Active Warning: Yes NOAA Scale: G3 - Strong NOAA

Space Weather Scale descriptions can be found at

www.swpc.noaa.gov/NOAAscales

SWPC WARNING DILUTION OF POSITION = “DOP”

UNITLESS PRN ERROR MULTIPLIER

HDOP = HORIZONTAL VDOP = VERTICAL PDOP = POSITION (HYPOTENUSE OF H & V) TDOP = TIME GDOP = GEOMETRIC (PDOP + TIME) RDOP = RELATIVE (REAL TIME PARAMETERS)

SATELLITES/ DOP WITH OBSTRUCTIONS

34

SATELLITES/ DOP WITH OBSTRUCTIONS

DUAL CONSTELLATION RT POSSIBILITIES: GPS ≥ 5, GLN = 0 GPS = 4, GLN = 2 GPS = 3, GLN = 3 GPS = 2, GLN = 4 (Can't initialize with only GLN Sats.)

GPS AND GLN

BEST SCENARIO = 7 OR MORE GPS

GLN “K” SATS WILL HAVE A CDMA (L3) FORMAT SIGNAL

WHAT ABOUT GLONASS? GNSS CAN HELP IN URBAN CANYONS

35

GNSS CAN HELP IN CORRIDOR SURVEYS GNSS CAN HELP IN OBSTRUCTED AREAS

Antenna

Type A

Antenna

Type B

Different

Phase Patterns

Note that SV elevation and

varying phase patterns affect

signal interpretation differently

36

RELATIVE & ABSOLUTE ANTENNA CALIBRATIONS

THE TECHNOLOGY SWEET SPOT

• SBAS: 2 M H, 6 M V, 0.3 M SMOOTHED H, CHEAP

• COMMERCIAL DGPS: FEW DM, $$

• USCG BEACON: METER+, CHEAP

• DIFFERENTIAL LEVELING: 2-4 CM, LABOR/TIME INTENSIVE, $$$

• GEODETIC LEVELING: mm, LABOR/TIME INTENSIVE, $$$$$

• USER BASE RTK: 2-4 CM H, 3-5 CM V, REQUIRES INITIAL INVESTMENT

• RTN: 3-4 CM H, 5-7 CM V, REQUIRES INITIAL INVESTMENT(BUT ½ OF RTK)

• AERIAL MAPPING: .10 M H, .20 M V, $$$

• LIDAR: 0.10 – 0.3 M V

• SATELLITE IMAGERY: 0.5 METER H RESOLUTION, 3 M LOCATION, $$$

• LOW ALTITUDE AERIAL IMAGERY: 2-4 CM H, 3-5 CM V, $$$

• TERRESTRIAL LASER SCANNING: PROJECT SITES ONLY, 0.015 M H, 0.02 M V, REQUIRES INITIAL INVESTMENT

LightSquared • LightSquared, formerly known as SkyTerra and Mobile

Satellite Ventures (MSV), is based in Reston, Virginia.

• LightSquared is deploying an open wireless $14 billion broadband communications system with uplink (base station to handset) signals operating in the 1525-1559 MHz frequency band.

• LightSquared plans to provide coverage to the entire United

States by deploying more than 40,000 ATC base stations by 2015.

• Recently, the Federal Communications Commission (FCC)

conditionally approved an application for a waiver allowing LightSquared to repurpose the satellite spectrum immediately neighboring Global Positioning System (GPS) for use ground-based transmissions via Ancillary Terrestrial Component (ATC).

• Report on possible GPS Interference to be submitted by

June 15

37

PROPOSED L1 BAND ALLOCATIONS FOR LIGHTSQUARED

1550.2 – 1555.2 Mhz

1526.3 – 1531.3 MHz

http://tmfassociates.com/blog

The Economic Benefits of

Commercial GPS Use in the U.S. and The Costs of Potential Disruption Nam D. Pham, Ph.D.

June 2011

DIRECT ECONOMIC BENEFITS OF GPS TECHNOLOGY ON COMMERCIAL GPS USERS ARE ESTIMATED TO BE OVER $67.6 BILLION/YEAR IN THE UNITED STATES $122.4 BILLION/YEAR 3.3 MILLION JOBS 5.8 MILLION JOBS AFFECTED DIRECT ECONOMIC COSTS OF FULL GPS DISRUPTION TO COMMERCIAL GPS USERS AND GPS MANUFACTURERS ARE ESTIMATED TO BE $96 BILLION PER YEAR IN THE UNITED STATES, THE EQUIVALENT OF 0.7 PERCENT OF THE U.S.

ECONOMY

38

URBAN AREA EXAMPLE PBO STREAMS

LOGARITHMIC

“LightSquared Can Complement GPS” Javad Ashjaee JAVAD GNSS Presentation to PNT Board November 9, 2011 Crowne Plaza Hotel,

Alexandria, VA

39

GROUND STATION SIGNAL vs SPACE GNSS SIGNAL

“LightSquared Can Complement GPS” Javad Ashjaee JAVAD GNSS Presentation to PNT Board November 9, 2011 Crowne Plaza Hotel, Alexandria, VA

MITIGATION PROPOSED BY JAVAD: “LightSquared Can Complement GPS”

Javad Ashjaee JAVAD GNSS Presentation to PNT Board November 9, 2011 Crowne Plaza Hotel, Alexandria, VA

40

GPS DIVERSIONS

http://www.groundspeak.com/

GNSS POSITIONING CHOICES- SUMMARY

STATIC – BEST POSSIBLE GNSS POSITION.

Sub-centimeter horizontal and 1-2 centimeters vertical precisions.

“Network session” style. Campaign static requires planning for

conditions and logistics. 30+ minute set ups. L1 possible, but dual+

frequency recommended. Requires your post processing or NGS

OPUS processing with certain requirements. Rapid or final orbits

available. OPUS-PROJECTS will enable network solutions, while

OPUS-S, OPUS-RS & OPUS-DB are point positions only.

NEAR REAL-TIME – FASTEST METHOD FOR SURVEY GRADE

POSITIONS. Typically 1 centimeter horizontal and 2 centimeters

vertical relative to the base. Few seconds to 3 minutes point

positions. Dependent on many variables, e.G. - Accuracy of

base/RTN, distance to base/RTN, relative weather, multipath, robust

communication, broadcast orbit data, shot comparisons, knowledge

& techniques of the user. Processing done in the rover in the field.

AUTONOMOUS - FASTEST METHOD FOR A BALLPARK POSITION.

3-5 meters. No phase differential processing is performed- uses code

or smoothed code point positions. Few seconds per position. Good

for raw navigation for point recovery. Note: future GNSS

constellations & signals may yield near decimeter accuracy.

CRADLE TO GRAVE GNSS!

Instead of looking for a traditional tombstone to mark the final resting place of a loved one, friends and relatives will be able to find the location of the deceased using a GPS device or mobile phone. "The park will look very natural, just grass and trees. There will be no headstones and instead people will be buried in the park and a GPS locator placed in the coffin,” Michael McMahon chief executive of the Catholic Cemeteries Board told ABC News.

GPS Helps Track Babies in Nurseries Hospitals all over the world are starting to use GPS to track newborns in their nurseries as a security measure.