Slide 1

Dr. Azhari bin Mohamed

Jabatan Ukur dan Pemetaan Malaysia

Jalan Semarak

50578 Kuala Lumpur

Malaysia

http://www.jupem.gov.my

( Telephone: +603 26170813

2 Facsimile: +603 26934084

+ Internet Email: azhari@jupem.gov.my

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90 75 60 45 30 15

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GPS

Kursus Apresiasi Amalan Kadaster 2017

11 September 2017M │ 20 Zulhijjah 1438H

Wisma LJT

Slide 2

GPS Overview

Global Positioning System (GPS) is a

system created as a Navigation System by

the U. S. Department of Defense and

transmits special radio signals from

specially equipped communication

satellites which can be received by special

receivers and processed along with earth-

based signals to accurately provide

location virtually anywhere on earth.

Slide 3

• GPS has many advantages over Traditional Terrestrial Surveying Techniques

• These traditional techniques rely on line of sight between the survey instrument and a target

– If an obstructions exists, it must be traversed around

• Typically distance measurement is limited to 5 Km

• Weather can limit operations. eg fog, rain etc

Traditionally,

Slide 4

• Weather Independent

• Does not require line of sight

• Gives high Geodetic Accuracy

• Can be operated day and night

• Quicker and requires less manpower

–Economical advantages

• Common Coordinate System

• Wide Range of Applications

• Competitively Priced

Why GPS ?

Slide 5

Sistem GPS

NAVigation Satellite Timing And Ranging Global

Positioning System

Sistem pasif

Dibiayai dan dikawal oleh US Department

of Defense

Dibangunkan untuk kegunaan tentera US

Satelit GPS mengeluarkan signal berkod

yang boleh diproses oleh Alat Penerima

GPS bagi mendapatkan kedudukan,

kelajuan dan waktu

Terbahagi kepada 3 segmen:

Segmen Angkasa

Segmen Kawalan

Segmen Pengguna

NAVSTAR GPS

Slide 6

GPS Overview

• NAVSTAR - Navigation Satellite with Timing and Ranging

• Global, all weather, 24hour, satellite based navigation, positioning and timing system

• Developed by US DOD, primarily for military purposes

• Passive ranging to satellites enables determination of user’s position and velocity and time

• Positioning accuracy - 1 mm to 100 m depending on type of receiver, user dynamics, observable and processing technique

• Two basic positioning services

PPS - Precise Positioning Service

SPS - Standard Positioning Service

Slide 7

Penentududukan GPS

Kedudukan dan Masa dari GPS

Guna 4 satelit untuk mendapatkan

kedudukan dan masa

Kordinat diberi oleh Alat Penerima GPS

didalam X, Y dan Z (Earth-Centred, Earth-

Fixed

Kordinat XYZ ditukar kepada latitud,

longitud dan ketinggian geodetik diatas

elipsoid WGS-84

Transformasi kordinat perlu dilakukan

bagi mendapatkan nilai didalam datum

tempatan, contohnya, MRT, RSO, Cassini

dsb

X,Y,Z (unknown)

X,Y,Z (known)

GPS – Global Positioning System

GLOBAL – Sejagat, seantero dunia boleh

diperolehi dimana-mana atas bumi

– tetapi tidak:-

• Dalam bangunan

• Bawah tanah

• Ketika hujan terlalu lebat

• Dibawah pokok atau didalam hutan yang tebal

• Di sekitar kawasan yang mempunyai transmisi

tinggi

• Didalam hutan batu

• Mana-mana sahaja yang tidak menerima isyarat

GPS secara terus

GPS – Global Positioning System

POSITIONING

• Dimana anda?

• Berapa laju?

• Mana arah?

• Berapa lama?

• Dari mana hendak kemana?

SYSTEM

• Komponen-komponen dan hubungan antaranya

Slide 10

GPS Operational Capability

• Initial Operational Capability (IOC)

Declared operational for use by the civil community - 8 December 1993 Anti-Spoofing (AS) - 31 January 1994 Selective Availability (SA) tests discontinued

• Full Operational Capability (FOC) Declared fully operational - 17 July 1995 24 block II/IIA satellites

Slide 11

NAVSTAR GPS

PECAHAN GPS

1. BUMI

• Jisim bumi

• Permukaan bumi

Slide 13

Datum, Kordinat dan . . .

Bumi Kita

Permukaan Bumi sangat irregular

dan senantiasa berubah

Datum Geodetik medefinasikan saiz

dan bentuk bumi serta origin dan

orientasi sistem kordinat bagi

memetakan bumi

Berlainan negara menggunakan

berlainan datum

Bumi dimodelkan sebagai Elipsoid

yang ditentukan oleh a (semi-major)

dan 1/f (flattening)

Slide 14

24 satellites operated by USAF provide 24-hour, all-weather, global coverage

Satellites are equipped with atomic clocks

Precise time signals are broadcast on L-band radio frequencies

Four satellite signals enable receivers to triangulate position

2. GPS Satellite

Slide 15

Satelit GPS Blok II

Berat: 930 kg

Saiz: 5.1 m

Kelajuan: 4 km/s

Signal L1 + L2 (1575.42 +

1227.60 Mhz)

Jangkahayat: 7.5 tahun

Slide 16

Block II

Satellite Launch :

1989 - 1997

Slide 17

How large is the GPS satellite ?

Slide 18

Block IIR

Satellite

• Replacement Block

• Launch Plan :

1997 - 2001

• SVN 43

Slide 19

GPS Satellite Programmes

• Block I Engineering test satellites - design life of 5 yrs First launch Feb 1978, last - Oct 1985 12 satellites built, by Rockwell, 11 launched Rb clocks on all, Cs on last four Available until 18 Nov 1995, average life 7.7

years • Block II/IIA Operational satellites - design

Slide 20

Konstelasi GPS

Konfigurasi 21 + 3

6 nearly circular orbits

4 satellites per / plane

55 inclination to equator

Ketinggian 20,200 km

Period 11j 58 m (12

sidereal hrs)

6 jam dlm pandangan

Slide 21

Satellite transmits data on two L-band frequencies

L1 = 1575.42 MHz = 19 cm

L2 = 1227.60 MHz = 24 cm

The carriers are modulated with two different ranging codes (transmitting information)

Civilian C/A Code, = 30 m ( L1 & L2)

Military P- Code, = 3 m ( L2)

GPS SATELLITE SIGNAL

Slide 22

3. GPS Ground Control

Slide 23

Operational Control System (OCS)

Rangkaian 5 buah stesen penjejak GPS

Mengawasi jam/masa

Menjejak satelit bagi pengeluaran efemeris satelit dan masa

• Menghantar maklumat tersebut ke satelit GPS & Alat Penerima GPS Tracking Stations

• Master Control Station

• Tracking Satellites

• System Integrity

• Atomic Clocks

• Atmospheric Data

• Satellite Almanac

Slide 24

• To decipher the GPS signals, the receiver must perform the following tasks: (Anon, 1989)

– selecting one or more satellites in view

– acquiring GPS signals

– measuring and tracking

– recovering navigational data

• There are two types of service available to GPS users - the SPS and the PPS

4. GPS Receiver

Slide 25

Terdiri daripada Alat-alat Penerima

GPS dan komuniti pengguna

Alat Penerima GPS menukarkan

signal GPS kepada kedudukan,

kelajuan dan masa

Alat Penerima GPS digunakan untuk:

navigasi (kapalterbang, kapal,

kenderaan, pengembara)

penentududukan (ukur dan

pemetaan, kawalan geodetik,

geodynamik)

penentuan masa (astronomi,

telekomunikasi, waktu piawai)

penyelidikan saintifik (atmosfera)

5. GPS Users

Slide 26

5. GPS Users

• Surveyors, engineers, scientist or

• Anybody that has GPS equipment for

– Vehicle Tracking Ambulance

– Navigation Police

– Mapping Cruise Ships

– Hydrography courier services

– Aircraft Approach/landing Delivery services

– Dredging Enhanced 911 (E-911)

– Salvage Hikers

– Oil Exploration Photogrammetry

Slide 27

1. Forestry and natural resources

- to identify and monitor the exact location of forest resources

- to determine the location of wildlife activity centers - to demarcate exact forest boundaries

2. Precision farming

- to locate precise soil sample points - to apply chemicals during aerial spraying at the

right spots, thus ensuring efficiency in chemical and fuel usage and productivity increase

- to map crop yields

GPS Potential Applications in Natural Resources and Environment

Slide 28

3. Monitoring deformations and land movements

- to monitor stability of man-made structures, such as dams, bridges, tall buildings etc

- to monitor hill slope stability, esp. along highways and near housing estates

- to monitor Earth plate motion 4. Monitoring ionosphere - part of atmosphere where gas ionization occurs, at

altitude between 50 to 1000km - related to TEC and varies according to time of day,

solar cycle and locality

GPS Potential Applications in Natural Resources and Environment

Slide 29

5. Airborne mapping

- to map large areas, coastal areas, forests and inaccessible areas, thus

- reducing the number of ground control points - eliminating damage to environment - GPS/LIDAR (light detection and ranging)

integration to obtain DEM - can be used at night, through cloud and can

penetrate to ground and forest areas - to monitor Earth plate motion

6. Vehicle navigation - GPS/digital road map to act as route guidance for vehicle location, finds best route - avoid traffic jams, reduce pollution and save fuel

GPS Potential Applications in Natural Resources and Environment

Slide 30

7. Cadastral surveying

- to establish property corners, boundaries and land parcels

- conventional techniques require extensive traversing and cause damage to environment, whilst GPS reduces clear-cutting

8. Utility mapping - to help electric, gas and water utility companies to

plan, build and maintain their assets - avoid traffic jams, reduce pollution and save fuel

GPS Potential Applications in Natural Resources and Environment

Slide 31

Basic Concept • GPS receiver needs signals

from at least 4 satellites to

calculate a 3D position.

• Three satellites are required to

determine XYZ coordinates.

• The receiver measures the distance

(time delay) to each satellite.

• It verifies the location of each

satellite in the sky, which is a known

factor.

• Using this data is able to triangulate

the precise location of the receiver.

Slide 32

Outline Principle : Range

Xll

Vl

Slide 33

Xll

Vl

Outline Principle : Range

Slide 34

Xll

Vl

Outline Principle : Range

Slide 35

Xll

Vl

Range = Time Taken x Speed of Light

Outline Principle : Range

Slide 36

We are somewhere on a sphere of

radius, R1

R1

Outline Principle : Position

Slide 37

2 Spheres intersect as a circle

R1

R2

Outline Principle : Position

Slide 38

3 Spheres intersect at a point

3 Ranges to resolve for Latitude, Longitude and Height

R1

R2

R3

Outline Principle : Position

Slide 39

• The satellites are like “Orbiting Control Stations”

• Ranges (distances) are measured to each satellite using time dependent codes

• Typically GPS receivers use inexpensive clocks. They are much less accurate than the clocks on board the satellites

• A radio wave travels at the speed of light

• (Distance = Velocity x Time)

– Consider an error in the receiver clock

• 1/10 second error = 30,000 Km error

• 1/1,000,000 second error = 300 m error

Outline Principle : Position

Slide 40

4 Ranges to resolve for Latitude, Longitude, Height & Time

It is similar in principle to a resection problem

Point Positioning

Slide 41

GPS Signal Structure

• Each GPS satellite transmits a number of signals

• The signal comprises two carrier waves (L1 and L2) and two codes (C/A on L1 and P or Y on both L1 and L2) as well as a satellite orbit message

Fundamental

Frequency

10.23 MHz

x 154

x 120

L1

1575.42 MHz

L2

1227.60 MHz

C/A Code

1.023 MHz

P (Y)-Code

10.23 MHz

P (Y)-Code

10.23 MHz

÷ 10

50 BPS Satellite Message (Almanac & Ephemeris)

Slide 42

Range Determination from Code Observations

D = V (DT)

• Pseudoranges (Code)

– Each satellite sends a unique signal which repeats itself approx. 1 msec

– Receiver compares self generated signal with received signal

– From the time difference (dT) a range observation can be determined

– Receiver clock needs to be synchronized with the satellite clock

DT

Received Code

from Satellite

Generated

Code from

Receiver

Slide 43

D = c DT + N

Range Determination from Phase Observations

• Phase Observations

– Wavelength of the signal is 19 cm on L1 and 24 cm on L2

– Receiver compares self-generated phase with received phase

– Number of wavelengths is not known at the time the receiver is switched on (carrier phase ambiguity)

– As long as you track the satellite, the change in distance can be observed (the carrier phase ambiguity remains constant)

DT

Received Satellite

Phase

Generated

Phase from

Receiver

Slide 44

Point Positioning

Accuracy 10 - 30 m

A receiver in autonomous mode provides

navigation and positioning accuracy of about

10 to 30m

Slide 45

One way ranging

• In GPS, one way ranging requires 2 clocks.

• Ranges measured with signals broadcast from GPS satellites to receivers.

• microwave part of the electromagnetic spectrum.

• Passive - satellites transmit signals, receivers receive.

• Thus no limit in simultaneous users.

• The system uses the time the signal travels from the satellite to the receiver to obtain distance between satellite and receiver.

• Range is actually “PSEUDORANGE” because of user clock bias.

Slide 46

Passive System

• Survey in GPS is like trilateration in conventional technique.

• Survey require a minimum of 4 satellites.

• The signals carry some kind of satellite identification. This is to allow identification of satellites and its location.

• The signal will tell receiver where to find other satellites.

• In brief, signal should tell receiver:

– what time it is on the satellite

– instantaneous position of moving satellite

– information about necessary atmospheric correction

– some sort of satellite identification.