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Mapwork Basic Skills.ppt
- 3. Types of spatial information
- 4. From… A Met hodology t o consider …photograph… …to orthophoto map… …to topographic map
- 5. What is a phot ograph? A det ailed and complet e pict ur e of 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 ography Photographs
- 6. Aerial Photographs AerialPhotographs Vertical High (horizon ) Oblique Low (horizon x )
- 8. Cape Town1926 1996 Historical Documents
- 9. 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 and correlat 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 south Orientation
- 11. Direction
- 12. What is a map? A map is a generalised and reduced represent at ion of (a port ion of ) t he curved surface of t he eart h on a flat surface Or t hophot o Map • a combinat ion of an aerial phot ograph and a map • a rect if ied image and t rue t o scale Orthophoto Maps How does t he ort hophot o map dif f er f rom t he vert ical aerial phot ograph?
- 13. • A let t er or symbol indicat ing a part icular f eat ure What is a convent ional sign? Conventional Signs (1) Point Line Area
- 14. 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
- 15. Symbol Brown
- 16. Symbol Blue
- 17. Symbol Green
- 18. Symbol Red
- 19. Symbol Black
- 21. • Contours • Trig. Stations • Spot Heights • Bench Marks Representation of Height
- 22. Slopes
- 23. 1 1 - 2 2 - Concave Convex Convex and Concave slopes
- 25. Equat or (0°) Nort hern Hemisphere Sout hern Hemisphere Nort h Pole (90° N) Sout h Pole (90° S) Latitude
- 26. WesternHemisphere EasternHemisphere GreenwichMeridian0° Sout h Pole (90° S) Nort h Pole (90° N) Longitude
- 27. EasternHemisphere WesternHemisphere Nort hern Hemisphere Sout hern Hemisphere S;E Latitude & longitude
- 28. A B C D A B C D A B C D 18° 00’ 18° 00’ 34° 00’ 34° 00’ 19° 00’ 19° 00’ 35° 00’ 35° 00’ 30’ 30’15’ 45’ 15’ 45’ 3418 1° = 60’ 1° Square Reference numbering – 1:50 000
- 29. 18° 45’ 34° 00’ 19° 00’ 34° 15’ 03’ 51’ 54’ 57’ 06’ 09’ 12’ 48’ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Reference numbering – 1:10 000 A C D A B C D 18° 00’ 34° 00’ B
- 30. • 1° = 60’ • 1’ = 60” 30” 20”10” 40”50” 30” 10” 20” 40” 50” 01’ 46’ 26° 46’ S; 29° 01’ E 26° 45’ 12” S; 29° 00’ 41” E Co- ordinates: from ° to ‘ to “
- 31. Met res 1 000 Kilomet res 0 1 2 3 Line Scale A B
- 32. 1:50 000 • This is a mat hemat ical way of expressing t he scale • Only numbers are used and it ref ers t o t he same unit of measurement Numerator • The numerat or is always 1 & represent s t he map Ratio Scale Denominator • The denominat or is always bigger & represent s t he ground
- 33. map dist ance in cm ground dist ance equivalent i.e. 50 000 100 000 E.g. 3,7 cm on t he t opographic map 3,7 x 50 000 100 000 = 1,85 km • To convert cm t o km you must divide by 100 000 (1km = 100 000 cm) • Conver t ing dist ance on t he 1:50 000 t opographic map: x 1:10 000 ort hophot o map 10 000 Converting cm to km 3,7 x 10 000 100 000 = 0,37km or 370m E.g. 3,7 cm on t he ort hophot o map
- 34. Finding north
- 36. Bench mark