Kesedaran GPS by ABM- SWG09

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Kesedaran GPS by ABM- SWG09

Postby rembau » 31 Mar 2011, 10:45

KESEDARAN GPS

Disediakan oleh
Goh Chee Seng & Chin Poh Yee@Botak Chin


INTRODUCTION – Navigation
= Navigation skills play an important role in every jungle trekking/recce
(Experiences, luck, time, team mates, team work….etc)
= in the old days
navigation without GPS is always difficult in rainforest
(topo map, compass, thick vegetation, cloud/mist)
= with GPS, navigation becomes easier.
(location can be obtained through satellite signals)




CHAPTER 1 – GPS (Global Positioning System)
The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. GPS works in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS.


1.1: How it works
GPS satellites circle the earth twice a day in a very precise orbit and transmit signal information to earth. GPS receivers take this information and use triangulation to calculate the user's exact location. Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user's position and display it on the unit's electronic map.


1.2: 2D & 3D
2D: A GPS receiver must be locked on to the signal of at least three satellites to calculate a 2D position (latitude N-S and longitude E-W) and track movement.

3D: With four or more satellites in view, the receiver can determine the user's 3D position (latitude, longitude and altitude).

Once the user's position has been determined, the GPS unit can calculate other information, such as speed, bearing, track, trip distance, distance to destination, sunrise and sunset time and more. (http://www8.garmin.com/aboutGPS/)


1.3: 6 parallel & current 12 parallel
August 1993 – ABM Kg Perwor – G Bilah – G Gerah Expedition.
Using 6 parallel GPS, at certain areas, Botak Chin has to climb tree to obtain GPS signal

Current 12 parallel GPS, can obtain GPS signal easily.

1.4: Advantage of modern GPS
Save waypoints & the whole journey (track) to SIM card. Can be used for future trips to trace back the old trail.

1.5: Setting of Coordinate System & Map Datum
Coordinate system: Primary – Lat/Lon (deg/min/mmm) WHY not setting second?
Secondary – RSO (if available)

Map Datum: Primary & Secondary – Kertau (West Malaysia)


1.6: New datum by JUPEM – Geocentric Datum of Malaysia (GDM 2000)

ABSTRACT
Global Positioning System (GPS) has emerged to become a vital component in high precision positioning suitable for survey and mapping. The advent of GPS and unified GIS applications over large areas have caused the existing MRT and BT68 datums to become obsolete, increasingly inefficient and difficult to relate to modern systems. Current trend also shows that many countries have implemented and adopted a geocentric coordinates reference frame for their geodetic datum. Therefore, there is a need to upgrade the current GPS network in Malaysia to a higher order network with connection to a precise geocentric reference system in the International Terrestrial Reference Frame (ITRF) which is more compatible with the space based systems.

The Geocentric Datum of Malaysia (GDM2000) is based on International Terrestrial Reference Frame 2000 at epoch ITRF2000@00.0 and is computed for 17 Malaysia Active GPS System (MASS) stations. The upgrading of the existing GPS Network has been carried out to provide geodetic grade infrastructure for the nation. This new Malaysia Primary Geodetic Network (MPGN) is connected to the International Terrestrial Reference Frame 2000 (ITRF2000) at centimeter level accuracy.

Brief concept of DATUM
“Historically, datums have been established in many regions around the world since the 19th Century using conventional surveying techniques and procedures. Most of them were confined to small areas of the globe, fit to limited areas to satisfy national mapping requirements. This is the case in Malaysia where it has two conventional geodetic datum, namely the Malayan Revised Triangulation (MRT) for Peninsular Malaysia (West Malaysia) and the Borneo Triangulation 1968 (BT68) for Sabah and Sarawak (East Malaysia). They are therefore regional in nature and generally are not aligned with global geocentric coordinates frames. “

(http://www.jupem.gov.my/JUPEM/GDM/pdf/G ... zation.pdf)


CHAPTER 2 – Topographic Map

Information in topographic maps is restricted.

2.1: Official Secret Act
“di bawah perlindungan Akta Rahsia Rasmi 1972…..Seksyen 2,3,4,5, 8 & 9…”

2.2: Description
1. Malaysia (Semenanjung)
2. Scale Grid unit Siri grid size
1: 50 000 (2cm: 1km) metres L7030 2cm
1: 63 360 (1 inch: 1 mile) metres L7010 1.578cm
1: 63 360 (1 inch: 1 mile) yards L7010 ~1.45cm

3. RSO grid (metres)
Rectified Skew Orthomorphic – One of the projection methods drawing grid lines of
topo map

Datum: Kertau 1948 (West Malaysia) Timbalai 1948 (Borneo)

Origin 4d N, 102d15’ E of Greenwich Origin 4 deg. N, 115 deg. E
472,854m E, 442,420m N

4. Name of map: Gunung Chamah (Example)
5. Terhad – Restricted
6. Lembar (sheet) 3765
Siri L7030
Edisi 1-PPNM (2-PPNM )


7.
Reading of coordinates

Longtitude
E – W

Latitude N - S

8. Terrain features

Contour lines
(20m/50ft/100ft)




Q8. How will GDM2000 affect existing maps?


A. Map details will experience about 200 metres shift, relative to the gridlines on the map. At 1: 50 000, the shift is barely significant at 4 mm. It is 20 mm at 1:10,000 scale.

(http://www.jupem.gov.my/GDM/FAQ/faq-gdm.htm)

CHAPTER 3 – Compass

A tool of showing direction

Magnetic North – direction North shown by compass
True North – true North of earth
Grid North – direction North of Grid line on Topo map


















CHAPTER 4 – Combination use/Case study

4.1: Signal “off”






4.2: Rivers







4.3: Observation of terrain/Adjustment/Direction







4.4: Trail drafting on Topo map
Dan Kami jadikan di bumi gunung-ganang yang menetapnya, supaya bumi itu tidak menggegar mereka; dan Kami jadikan di celah-celahnya jalan-jalan laluan, supaya mereka mendapat petunjuk.(Surah Al-Anbiyaa':31)

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