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GIS & History of Mapping in Malaya (lecture notes circa 2009)

History of mapping in Malaysia. My lecture notes for public health field posting in 2009. Never updated. My apologies.

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GIS & History of Mapping in Malaya (lecture notes circa 2009)

  1. 1. Präsentat ion Geographical Information System (GIS) & History of Mapping in Malaya Dr Azmi Mohd Tamil Universiti Kebangsaan Malaysia (National University of Malaysia) https://drtamil.me Incidence Mapping Geographical Information System Global Positioning System
  2. 2. What is GIS? A computer system for capturing, storing, checking, integrating, manipulating, analysing and displaying data related to position on a surface. AGI GIS Dictionary (http://www.geo.ed.ac.uk/agidic/welcome.html)
  3. 3. GIS (Geographic Information System) • Geographic  Maps • Information  Database • System  Hardware, Software, Data, People, Plans/Programs GIS combines the intuitive visual clarity of a map together with the information structuring, searching and analysing power of a database.
  4. 4. Layers for GIS Other Thematic Data Elevation Geodetic Control Imagery Government Units Hydrography Transportation Cadastral Framework or Core Data Spatial Data Social Economic Biological Landcover Demographic Flood Zones
  5. 5. GEOGRAPHIC INFORMATION SYSTEM 1 2 3 4 ID Name Pop_90 MMR 1 … 1897 4.5 2 … 2345 5.6 3 … 1293 1.2 4 … 560 6.7 … 480 000 494 500 Spatial Data Linked With Tabulated Data
  6. 6. GIS in Health • Possible applications include mapping the health of populations, identifying patterns of disease transmission, and locating foci of risk. Geographical methods can also be applied in health administration and health economics.
  7. 7. Early Use of GIS in Health • In 1854 Dr. John Snow was able to pinpoint a cause of cholera outbreak In London by the following: “…He went to the Register of Deaths and got details of all the deaths from cholera in the Golden Square, Berwick St and St Anne's, Soho, districts and plotted the distribution of deaths in London on a map. He determined that an unusually high number of deaths were taking place near a water pump on Broad Street. Snow's findings led him to petition the local authorities to remove the pump's handle. This was done and the number of cholera deaths was dramatically reduced…” • The work of Doctor Snow stands out as one of the most famous and earliest cases of geography and maps being utilized to understand the spread of a disease. http://www.bbc.co.uk/history/historic_figures/snow_john.shtml
  8. 8. Early use of GIS in Health ;-) • Outbreak of Cholera in London, 1854 • Spot map of the cases by John Snow
  9. 9. Measuring Spatial Data GPSr – How does it work? How accurate is it?
  10. 10. GPS Receivers
  11. 11. What is Global Positioning System (GPS) ? A very precise positioning system • Developed and maintained by the US Department of Defense (DOD) • Satellite Based * 24 satellites * 20,200 km high orbit
  12. 12. Segments of GPS Source:Trimble 1. Space Segment A constellation of 24 satellites
  13. 13. How GPS Works ……… Uses measurements from 4+ satellites Distance = travel time x speed of light Source:Trimble
  14. 14. Determining GPS Position • Suppose the distance from Satellite A to our position is 11,000 miles • At this point we could be located anywhere on the specified sphere Satellite A + • Next, let us take another measurement from a second satellite, Satellite BSatellite B + • Now our position is narrowed down to the intersection of theses two sphere
  15. 15. Satellite C + Determining GPS Position Satellite A Satellite B + + • Taking another measurement from a 3rd satellite narrows our position down even further, to the two points • So by ranging from 3 satellites we can narrow our position to just two points in space • These points are located where the 3rd sphere cuts through the the intersection of first two spheres
  16. 16. Satellite C + How do we decide which one is our true location? Satellite A Satellite B + + • We could make a 4th measurement from another satellite to determine the true point • However, GPS receivers use a 4th satellite to precisely locate our position • We can eliminate one of the two points that gives a ridiculous answer • The ridiculous point may be too far from the earth OR
  17. 17. GPS • GPS: uses satellites to pinpoint the location of receivers on earth. Handheld Navigation
  18. 18. How accurate is GPS? Depends on some variables • Design of receiver • Relative positions of satellites, technically known as PDOP (Position dilution of precision) • Post-processing • Time spent on measurement
  19. 19. Possible Source of Inaccuracies • Satellite clocks (atomic) • Atmospheric delays • Multi-path • Receiver clocks (time recalibrated upon receiving good signal from satellites). • PDOP • SNR GPS Error Sources Receiver Clock Error 1000 L1 L2 9 6 3 12 9 6 3 12 Satellite Clock Error including Ionospheric refraction Multi-path Tropospheric Delay Satellite Orbit Error ? ? ?
  20. 20. Multipath • When GPS signals arrive at the receiver having traveled different paths
  21. 21. What is a PDOP? • Position Dilution of Precision Good PDOP Poor PDOP
  22. 22. SNR (signal-to-noise ratio) • SNR determines the signal strength relative to noise • GPS position is degraded if the SNR of one or more satellites in the constellation falls below certain range Signal Strength Indicators
  23. 23. How Accurate is the Spatial Data? • If we want sub-meter accuracy, then we would have to use specialised GPSr surveying equipment such as; – DGPS (Differential GPS) - higher accuracy in terms of position. It gets differential data live from a ground base station (Kuantan) and compare them with the actual current position, using some algorithm to get a better accuracy. Additional hardware required and not available for Garmin GPSr. – MyRTKnet - a nation-wide GPS network and system infrastructure developed for GPS users to provide RTK and DGPS services with unmatched accuracy. A wide-area satellite based service, the broadcast My RTKnet corrections can be obtained anywhere in Malaysia using a custom-built MyRTKnet GPS receiver. – P-DGPS (Post-Processing Differential GPS) works the same way, but not in real time. You would store your data elsewhere (storage card, PPC on Notebook), then compare them with data registered by a nearby MASS station at the same time you recorded yours. This recalculation would give you a below 1 meter accuracy.
  24. 24. DGPS with sub-meter accuracy
  25. 25. SIRFstarIII • Instead we will use a medium cost GPSr with SIRFstar III chip which give us an accuracy of within 3 meters or less (USD540) • It has a horizontal position accuracy of less than 2.5m. Supports multiple reference frequencies. Also supports SiRFDRive dead reckoning technology for enhanced positioning accuracy and availability.
  26. 26. How Accurate is the Spatial Data? To reduce inaccuracy, the spatial measurement should be; • Taken with a SIRFstarIII GPSr such as Garmin GPSMap 60Csx. • GPSr properly configured – i.e. Map Datum = WGS84 for own map, or Kertau 48 if using JUPEM maps. • For mapping; – Using an external antenna – Tracking interval on GPSr set to every 1 second – Locked-On-Road=OFF – done using active log tracks only (ie. not using the tracks that are saved to the GPSr)
  27. 27. History of Mapping in Malaysia
  28. 28. History of Mapping • The first attempt at triangulation survey was made in Penang in 1832 by Lieutenant Woore of the Royal Navy. • In 1885, H.G. Deanne, a contract surveyor from Ceylon, was appointed by the Public Works Department, Perak, to carry out the Trigonometrical survey of Perak. He measured the 4.6 mile Larut baseline and carried out astronomical determinations for latitude and azimuth near Taiping. • This Trigonometrical Survey in Perak together with the Penang and Province Wellesley triangulations and Malacca Triangulation (1886- 1888), laid the foundation of the existing control framework. These foundations were still primitive, progress was frequently sporadic and much of the work was found to be substandard. However, by the end of 1901, the Major Triangulation of Perak and Selangor had been completed and work had been in progress in Negeri Sembilan since 1899. This period also witnessed the commencement of trigonometrical surveys in various parts of the country.
  29. 29. MRT48 & MRT68 • However, the quality of the early works were so inconsistent that it was decided to re-observe the principal triangles of the general triangulation with the object of bringing the work up to modern standards. • This triangulation scheme in Peninsular Malaysia was known as the Primary or Repsold Triangulation which was completed in 1916. • In 1948, it was replaced by a new system known as the Malayan Revised Triangulation (MRT). This was followed by a lengthy process of additional measurements and recomputation until 1968. • As a result, this system is then referred to as MRT68. On the other hand, the geodetic network used in Borneo is called the Borneo Triangulation (BT68).
  30. 30. American Mapping Service • In 1965, the American Mapping Service (AMS) carried out an internal re-adjustment of the MRT in order to connect it to the South East Asia Datum (SEA Datum). In 1965, AMS re-adjusted the MRT data in the South East Asia Datum using three triangulation points in Thailand held fixed.
  31. 31. World Geodetic System 1972 • In 1978, the British Army Survey carried out a Doppler campaign in Peninsular Malaysia, Sabah and Sarawak in order to connect the local network to the World Geodetic System 1972 (WGS 72). The network consists of 5 points of the MRT and 5 points of BT68. The given accuracy is of the order of three metres. However, the observations were never used for any re-adjustment of the MRT and BT68.
  32. 32. STRE 1993 • In November 1993, a group from the Squadron of Technical Royal Engineers (STRE) of the United Kingdom observed with TRIMBLE GPS L1/L2 receivers on 5 existing Doppler points and 9 new GPS stations in Peninsular Malaysia. • In addition to that, 7 existing Doppler points and 4 old trigonometric stations were also observed in Sabah and Sarawak. • The aim is to establish better transformation parameters from Doppler to WGS84 for the region and to connect Peninsular Malaysia to Sabah and Sarawak. • In Dec, 1993, the GPS observations were successfully completed and computations and analysis were subsequently conducted based on the WGS84 reference frame. • Results of STRE adjustments show that the absolute accuracy of WGS84 coordinates is at the 1m level for the X,Y and Z axes respectively.
  33. 33. GEODYSSEA Project • This project which was initiated in 1994 and was completed in 1997, was to study the plate motion and crust deformation in the region of the South and South East Asia. • GPS campaigns were carried out in December 1994 and April 1996 to study such motions. This is followed by a GEODYSSEA Symposium in April 1997 in which results of the campaign were tabled and discussed. • Even though the GEODYSSEA project was officially terminated in 1997, the studies in the geodynamics of the region were still pursued with a GPS campaign carried out in October 1998. The purpose of the endeavour was to further gauge and confirm the plate movements in the region as initiated by the GEODYSSEA project. • With the availability of such data, a time series dynamics of the region could be collected and studied. From the two GPS campaigns of 1994 and 1997, a zero order network had also been able to be set-up in Malaysia with coordinates referring to ITRF94 and ITRF96 and with an absolute accuracy of better than ± 3cm.
  34. 34. Map Datum Difference between Kertau 48 & WGS84
  35. 35. Earth Surfaces Geoid Ellipsoid
  36. 36. Earth Surfaces Ellipsoid Terrain Geoid
  37. 37. Datums • A geodetic datum is a reference model of the Earth, designed to fit all or part of the geoid • Datums provide the surface to which ground control measurements are referred, and are used as reference systems for navigation, surveying and mapping • A datum is defined by a specific ellipsoid and a unique point of origin Origin
  38. 38. Common Datums Name Ellipsoid Origin WGS 84 WGS 84 Earth’s centre of mass NAD 27 Clarke 1866 Meades Ranch, KS NAD 83 GRS 80 Earth’s center of mass (BIH BTS-84)
  39. 39. Regional Datums North American Datum Clarke 1866 South American Datum International Arc Datum Clarke 1880 European Datum International WGS72 Datum Tokyo Datum Bessel Most widely used local Datum/Ellipsoid pairs
  40. 40. The WGS 84 Ellipsoid
  41. 41. Reference point of other datums Ellipsoid
  42. 42. So WGS 84 is no longer a mystery…… How about Kertau 48?
  43. 43. History of M’sian Map Datum • In the past, before the advent of GPSr and the GPS satellites, mappers determined the coordinates of an origin as best as they could, then they measured the distances and the bearings of other places, using the origin as the reference point. Even with the best possible method that they have, the coordinates of the origin may be incorrect.
  44. 44. Kertau • For example the origin for our national map datum used to be Kertau. • Why Bukit Kertau? Although it is not the highest point (only 269.3m), it is centrally located in Peninsular Malaysia.
  45. 45. GEODETIC DATUMS Datum Kertau 1948 or MRT 1948 Coordinate Frame 77 positions of Repsold Triangulation, orientation at Kertau, scale very few. Reference Ellipsoid Modified Everest Origin at Kertau (ξ=0, η=0, N=0) P. Malaysia
  46. 46. Kertau Measurement Disparity REPSOLD Main Triangulation 1913- 1916 N 3o 27' 53.96" E 102o 37' 24.65" Malayan Revised Triangulation 1948 (MRT48) 1948 N 3o 27' 50.71" E 102o 37' 24.55" MRT68 1965 N 3° 27 ' 50.71" E 102o 37' 24.55" WGS 84 STRE 1993 N03o 27' 49.911" E102o 37' 18.943" ITRF 94 GEOD YSSEA 1996 N03o 27' 49.893" E 102o 37' 18.936"
  47. 47. Kertau “Moved” • 1 longitudinal degree is roughly 111.324 km. Since 1913, Kertau has "moved" roughly 177m. • Peninsular maps using MRT48 has to be "moved" (corrected) almost 200m to the North-West to correct the coordinates to conform with WGS84.
  48. 48. 10 coordinate systems in Malaysia 1. Old Cassini-Soldner for Peninsular Malaysia (E, N) 2. Old Rectified Skew Orthomorphic for Peninsular Malaysia (E, N) 3. Old Rectified Skew Orthomorphic for East Malaysia (E, N) 4. Malayan Revised Triangulation (f, l, h) 5. Peninsular Malaysia Primary GPS Network (f, l, h and X, Y, Z) 6. East Malaysia Primary GPS Network (f, l, h and X, Y, Z) 7. Geocentric Datum of Malaysia (f, l, h and X, Y, Z) 8. New Cassini-Soldner for Peninsular Malaysia (E, N) 9. New Rectified Skew Orthomorphic for Peninsular Malaysia (E, N) 10. New Rectified Skew Orthomorphic for East Malaysia (E, N)
  49. 49. Most Maps Are MRT68 • From MRT68, map projections were done using Rectified Skew Orthomorphic (RSO). • For cadastres, Cassini Soldner were used. • The existing Cassini projection system used for cadastral application in the Peninsular is based on local MRT datum.
  50. 50. Types of Projections
  51. 51. 9 Peninsular State Cassini-coordinate systems • The latitude and longitude of the origins are not referred to a single triangulation system but 9! Gunung Perak for Perlis & Kedah Fort Cornwallis for Penang & Province Wellesly Hijau Larut for Perak Bukit Asa for Selangor/Kuala Lumpur Gun Hill for Melaka & N. Sembilan Gunung Belumut for Johor Gunung Sinyum for Pahang (not Kertau!) Gajah Trom for Terengganu Bukit Panau for Kelantan • That is why we have to ask what is the datum of the map being used (i.e. MRT48/MRT68) since the conversion of the coordinates of the GPSr differ according to the datum.
  52. 52. Adopt GDM2000 • Since then, we have progressed to PMGGN (WGS84) in 1989. Now in 2003, JUPEM have adopted GDM2000 (GRS80). • The introduction of GDM2000 will have a significant effect on the topographical mapping products : the coordinates (shift) of points by up to approximately 200 meters in northeasterly and northwesterly directions for Peninsular and East Malaysia, respectively.
  53. 53. Geocentric Cassini Coordinate System • With the adoption of GDM2000, the existing Cassini projection system used for cadastral application will be converted to Geocentric Cassini Coordinate System. • For topographical mapping application in Malaysia, conversion will be done from RSO & Borneo RSO into Geocentric RSO Coordinate System.
  54. 54. 9 New Origins • To assist in the process, nine new origins (9 primary GPS stations) are selected in the vicinity of the old origins with their coordinates accurately defined in the GDM2000. The new origins are; GP58 Institut Haiwan,Kluang GP12 Lubuk China, Melaka GP31 Kuala Mai, Jerantut MASS Station Wisma Tanah, Jalan Semarak, Kuala Lumpur P253 Kg. Matang, Hulu Terenganu P314 TLDM Georgetown TG35 Gunung Perak, Kuala Muda TG26 Gunung Larut Hiijau, Taiping P222 Ulu Kelantan
  55. 55. Conclusion • Ask what is the datum of the map being used (i.e. MRT48/MRT68) since the conversion of the coordinates of the GPSr differ according to the datum. • Otherwise we may end up 193 meter away from the correct position.

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