Mapwork Basic Skills.ppt

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Department Land Affairs South Africa

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Mapwork Basic Skills.ppt

  1. 1. Types of spatial information
  2. 2. From…A Met hodology t o consider…photograph……to orthophoto map……totopographic map
  3. 3. What is a phot ograph?A det ailed and complet e pict ur eof a sect ion of realit y.Types of phot ographs• Hor izont al or t err est r ial• Sat ellit e I mage• Aerial Phot ographyPhotographs
  4. 4. Aerial PhotographsAerialPhotographsVerticalHigh (horizon )ObliqueLow (horizon x )
  5. 5. Aerial photography
  6. 6. Cape Town1926 1996Historical Documents
  7. 7. To orient at e yourself is t o est ablish your posit ion• “oriens” (Lat in) - rising of t he sun or east• f ind dist inct ive landmarks andcorrelat e phot ograph wit h act ual landscape• orientation in terms of direction -cardinal points of the compass• in South Africa shadows fall to the southOrientation
  8. 8. NSEWNW NESESWDirection
  9. 9. Direction
  10. 10. What is a map?A map is a generalised and reducedrepresent at ion of (a port ion of ) t hecurved surface of t he eart h on a flatsurfaceOr t hophot o Map• a combinat ion of an aerialphot ograph and a map• a rect if ied image and t rue t o scaleOrthophoto MapsHow does t he ort hophot o map dif f er f romt he vert ical aerial phot ograph?
  11. 11. • A let t er or symbol indicat ing a part icular f eat ureWhat is a convent ional sign?Conventional Signs (1)Point Line Area
  12. 12. Conventional Signs (2)Making it easier:Dist inguish bet ween t wo t ypes of landscape:• t he nat ural / physical landscape• t he const ruct ed / human landscape• Five colours- Brown- Blue- Green- Black- Red
  13. 13. SymbolBrown
  14. 14. SymbolBlue
  15. 15. SymbolGreen
  16. 16. SymbolRed
  17. 17. SymbolBlack
  18. 18. • Contours• Trig. Stations• Spot Heights• Bench MarksRepresentation of Height
  19. 19. Slopes
  20. 20. 11 -22 -ConcaveConvexConvex and Concave slopes
  21. 21. Equat or (0°)Nort hern HemisphereSout hern HemisphereNort h Pole(90° N)Sout h Pole(90° S)Latitude
  22. 22. WesternHemisphereEasternHemisphereGreenwichMeridian0°Sout h Pole(90° S)Nort h Pole(90° N)Longitude
  23. 23. EasternHemisphereWesternHemisphereNort hern HemisphereSout hern HemisphereS;ELatitude & longitude
  24. 24. A BC DA BC DA BC D18° 00’18° 00’34° 00’ 34° 00’19° 00’19° 00’35° 00’ 35° 00’30’30’15’ 45’15’45’34181° = 60’1° SquareReference numbering – 1:50 000
  25. 25. 18° 45’34° 00’19° 00’34° 15’03’51’ 54’ 57’06’09’12’48’1 2 3 4 56 7 8 9 1011 12 13 14 1516 17 18 19 2021 22 23 24 25Reference numbering – 1:10 000AC DA BC D18° 00’34° 00’B
  26. 26. • 1° =60’• 1’ = 60” 30”20”10” 40”50”30”10”20”40”50”01’46’ 26° 46’ S;29° 01’ E26° 45’ 12” S;29° 00’ 41” ECo- ordinates: from ° to ‘ to “
  27. 27. Met res1 000Kilomet res0 1 2 3Line ScaleAB
  28. 28. 1:50 000• This is a mat hemat ical wayof expressing t he scale• Only numbers are used and it ref ers t ot he same unit of measurementNumerator• The numerat or is always 1& represent s t he mapRatio ScaleDenominator• The denominat or is always bigger& represent s t he ground
  29. 29. map dist ance in cm ground dist ance equivalent i.e. 50 000100 000E.g. 3,7 cm on t het opographic map3,7 x 50 000100 000= 1,85 km• To convert cm t o km you must divide by 100 000 (1km = 100000 cm)• Conver t ing dist ance on t he 1:50 000t opographic map:x1:10 000ort hophot o map10 000Converting cm to km3,7 x 10 000100 000= 0,37km or 370mE.g. 3,7 cm on t heort hophot o map
  30. 30. Finding north
  31. 31. Trigonometrical Station
  32. 32. Bench mark

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