General questions.

How do you distinguish between commercial farming and subsistence farming on a 1:50 000 topographic map?

Commercial farming	Subsistence farming
·        The farm will usually have a name. ·        Farm road to farm buildings connecting with formal roads (e.g. secondary road) ·        Many farm buildings ·        Advance farming features such as dams, canals, windpumps, silos. ·        Large cultivated lands (use of tractors) ·        Cultivated lands have geometric shapes (tractors can plow in straight lines)	·        No names ·        No or few “other roads” not connected to formal roads. ·        No farm buildings, only huts ·        No advanced farming features such as dams, canals, windpumps (don’t have the capital or technology to build these). ·        Small cultivated lands and fragmented. ·        Irregular shaped cultivated lands due to the use of basic ploughing methods.

Mapwork slide

Mapwork calculations from fenslin

Heights and contour lines

Heights can be indicated in FOUR ways on a topographic map.

1.     Contour lines - lines (brown) joining areas with the same height above sea level. The contour interval (difference between contour lines) on a 1:50 000 topographic map is 20m.

2.     Spot heights - indicated by a black dot and height value (in meters above sea level) of a specific point on a topographic map.

3.     Trig. beacons (triangulation station or trigonometrical point) - indicated by a triangle which shows its unique number and height above sea level up to one decimal of a meter.

A Trig. beacon

4.     Bench marks - indicated by an arrow pointing to a main road with the height in meters above sea level.

Aerial Photographs

Aerial photographs are photos taken from light airplanes. These photos contain more detail e.g. orthophoto maps. Because it shows more detail the scale will be a large scale in comparison to a topographic map with less detail (small scale).

Three kinds of aerial photographs can be found –

• Vertical photographs
• Horizontal photographs
• Oblique photographs

Mapwork slide

Mapwork calculations from fenslin

Mapwork in the exam

Working through old IEB exam papers it becomes clear that certain questions always appear in the mapwork question papers. The 1:50 000 range topographic maps are used in the exams and the projection used to create these maps is the Gauss Conform Projection. Also indicated on the topographic map is
the central meridian used for this projection.

Distance, gradient and time calculations are always asked. Expect to get a'magnetic bearing' calculation!
Make sure you know how altitude is indicated on a topographic map – contour lines (with a contour interval of 20m), spotheights, trigonometry beacons and benchmarks. You will need this in order to calculate the gradient, to spot the highest point on the map and to describe the general gradient or elevation of an area.

The scale of the orthophoto map is five times smaller than that of the topographic map. A scale of 1:10 000 is a large scale and 1:50 000 is a small scale.

Formal cross-sections are usually to time consuming and rarely asks, however, sketch cross-sections are asked often. A sketch cross-section (free hand) is a sketch of what you see on a photo and not a precise graph.

Settlement questions are very common with questions about the type of rural settlements (isolated or nucleated) and farming activity (intensive or extensive). Land use zones must be identified such as CBD, rural-urban fringe, industrial area and their positions explained.

With GIS you will have to suggest themes (layers) that you would use in a presentation about a specific area. It is very important that you know the relevant concepts for GIS!

Street Patterns

Street patterns are a feature of urban areas which we can't live without. Street patterns can make it easy to travel around in the city, it can cause heavy traffic congestion or make it very difficult to locate a place.
There are THREE general types of street patterns -

• Grid iron
• Planned irregular
• Cobweb

1. Grid iron:

Usually found in the oldest part of the city (CBD). This pattern is characterized by rectangular street blocks.

Problems:

• Many intersections that can cause traffic congestion
• Uninteresting design
• Can lead to long and steep roads

Advantages:

• Easy to navigate around
• Easy to extend streets
• Easy to subdivide stands and to build on

2. Planned Irregular

Usually found at the latest suburbs and where there are steep slopes.

Problems:

• Difficult to extend streets
• Can easily get lost

Advantages:

• Interesting pattern
• Dangerous with hidden entrances

3. Cobweb

Streets radiate outwards from one central point e.g a plain, lake, dam, park

Where on earth are you?

A geographic coordinate system is a coordinate system that enables every location on the Earth to be specified by a set of numbers. The numbers represent the exact latitude and longitudinal position. If you look at a Gps every object will have a specific position where a latitude and a longitude intersect,

Doesn’t matter where on the earth you find yourself, you will have a latitude and longitudinal position. In South Africa your latitude position will always be south (South Africa is positioned between 22˚ & 35˚ South and 16˚& 33˚ East). Your latitude reference will always be South and longitude reference East. E.g. 27˚38’27’’ S and 30˚18’49’’E.

How do I determine my coordinates on a topographic map?
 
As mentioned before you always give the latitude first and then the longitude.
Step 1: Identify the the object on the topographic map
As mentioned before you always give the latitude first and then the longitude.


Step 1: Identify the object on the topographic map

Step 2: Look at the top of the map and find the latitude (23˚S) and the longitude (33˚E).

Step 3: Find the minutes by looking at the latitude and longitude immediately above (17’) and to the left (25’) of the object. Your coordinate thus far is 23˚17’S and 33˚25’E

You are not yet done, as you need to calculate the seconds.

Step 4: In the grid block where your object is situated measure the following (see diagram)


Latitude: a ÷ A = answer x 60 = C

Longitude: b ÷ B = answer x 60 = D

Therefore, coordinate for spot is –

23˚17’C”South and 33˚25’D”East

 
Latitude: a ÷ A = answer x 60 = C''


Longitude: b ÷ B = answer x 60 = D''

Therefore, coordinate for spot is –

23˚17’C”South and 33˚25’D”East

Map code

How to find the map code
To be able to find the map code of a particular map it is important to understand what the map code represents
E.g.2627 CC SKANDINAWIËDRIF
26 represent the first latitude
27 represent the first longitude

The grid block formed by the latitude and longitude above is divided into 4 blocks of equal size represented by A, B, C and D
The first letter represents one of the four ‘big’ blocks, in this case block C
The second letter represents the third block within big block C which is divided into four smaller blocks A, B, C and D

South Africa is divided into a series of grid blocks consisting out of latitudes and longitudes as can see on the map below (Map 1).

To find Skandinawiëdrif on the map you need to locate the intersection between the latitude 26˚ and the longitude 27˚. Now divide the grid block into four blocks, find block C which in turns is divided into four smaller blocks. Now find small block C. There you go, you have located Skandinawiëdrif by using its map code.

Topographic map interpretation

A. Geomorphology
1. Steep gradient
2. Gentle gradient
3. Convex slope
4. Concave slope
5. Conical hill
6. Butte
7. Mesa
8. Dip slope
9. Scarp slope
10. Homoclinal ridge
11. Valley
12. Spur
13. Poort
14. Cliff
15. Saddle/ col
16. Waterfall
17. River channel characteristics
18. Braided stream
19. Drainage patterns
20. Superimposed drainage
21. Slope elements

B. Settlements and Economic activities
1. Types of towns
1.1. Mining town
1.2. Central place town
1.3. Tourist town
2. Rural settlements patterns
2.1. Isolated
2.2. Nucleated
3. Farming methods
3.1. Commercial
3.2. Subsistence
4. Farming techniques
4.1. Intensive
4.2. Extensive
4.3. Fruit
5. Land use zones
5.1. CBD
5.2. Industrial
5.3. Residential – high/ low income
5.4. Rural-urban fringe
6. Informal settlements
7. Tourist destinations
8. Choice of site

C. Environmental issues and Climatology
1. North/south facing slopes
2. Valley inversion / pollution dome
3. Anabatic/ katabatic winds
4. Erosion
5. Droughts / seasonal rainfall
6. Type of rainfall

A. Geomorphology
1. Steep gradient
· Steeper terrain will have closely spaced contour lines.

2. Gentle gradient
· Flatter areas will have more widely spread contour lines.

A uniform slope is a slope with evenly spaced contours, it can be for hills of any gradient, weather it is steep or gradual, but they have to be evenly spaced.

3. Convex slope
· Contour lines close together at foot of hill
· Contour lines far apart near the crest (top)

4. Concave slope
· Contour lines close together at top of hill
· Contour lines far apart near the foot of the hill

5. Conical hill
· Circular shape contour lines
· Small crest

6. Butte
· Small flat top
· Height is 2x greater than width

7. Mesa (table mountain)
· Large flat top
· 2x wider than the height
· Resistant rock layer at top – dolerite/ granite

8. Dip slope and 9. Scarp slope
• Dip slope = gentle slope of mountain
• Scarp slope = steep slope of mountain

10. Homoclinal ridge
· A mountain with a clear dip and scarp slope

11. Valley and 12. Spur
• Valley = contour lines bend (V) towards the top of mountain
• Usually a non-perennial stream flowing down
• Spur = contour lines bend towards the foot of mountain
• Flank on both sides of a valley

13. Poort; 14. Cliff; 15. Saddle (col)

16. Waterfall

17. Stream channel characteristics
· Turbulent flow – in upper course / steep gradient / in a valley
· Laminar flow – lower course / flat gradient
· Upper course – in valley / steep gradient / straight channel
· Lower course – large meanders / oxbow lakes / large, wide floodplain / braided streams
· Outer bank – faster flowing water / more erosion / under cutting (also undercut bluff)
· Inner bank – slower flowing water / more deposition (also slip-off slope)

18. Braided stream
· Stream in lower course
· Carries large amount of stream load and sediments
· Deposition occurs due to decrease in slope and stream volume
· Deposition obstructs own flow
· Stream break up in smaller channels to flow round obstructions / sand banks or islands

19. Drainage patterns

20. Superimposed drainage

The course of the river is unrelated to the present underlying geological structure

The river exposed an older underlying land structure

21. Slope elements

B. Settlements and Economic activities
1. Types of towns
· Mining towns: Town developed because of mining activities e.g. Postmasburg, Kuruman, Hotazel, Venterspos
· Central place towns: Small towns delivering services to surrounding farming community
· Tourism towns: Mostly small towns along the coast, towns where you find warm underground water

2. Rural settlements patterns
· Isolated/ dispersed settlements – farmsteads far apart / mostly in dry regions with low carrying capacity
· Nucleated settlements – farmsteads close together / small farms in wet regions with high carrying capacity

3. Farming methods
· Commercial farming – farm to produce a surplus to sell to a market / farms with names, roads, windmills, dams, canals / fire breaks / silos and mills / cut lines
· Subsistence farming – farm to produce only enough for own use / no roads, name, dams, small fragmented cultivated lands/ fields have few straight boundaries / numerous footpaths / huts

4. Farming techniques
· Extensive – large farms in dry regions / low carrying capacity
· Intensive – small farms in wet regions / high carrying capacity

5. Land use zones
· CBD – where main roads converge / oldest part of town with monuments / grid street pattern
· Industrial – large buildings / outskirts of town / railway lines
· Residential – oldest and lower income have grid street pattern / newer, higher income have irregular street pattern, steep slopes, view over golf course or natural environment
· Greenbelts – areas where natural environment is kept and preserved / no development allowed / e.g. river floodplains; hills and mountains
· Recreation (Rec) – areas used for recreational purposes / e.g. sport grounds; park
· Rural urban fringe – areas surrounding build up areas (town) / here we find mixture of urban and rural functions / e.g. graveyards; golf course; sewerage works; brickworks; agricultural holdings; aerodrome; etc.

C. Environmental issues and Climatology
1. Aspect

•  North facing slopes – receives direct sunlight / warm
•  South facing slopes – in the mountain shadow / cooler

2. Valley climates
Valley breezes – anabatic wind blows during the day, up slope / katabtic wind blows at night, down slope / cold temperatures (frost pocket forms in bottom of valley

4. Pollution – industries situated in bottom of valleys / pollution trapped

5. Erosion
· Occurs along steeper slopes
· Little vegetation increase rate of erosion
· Wind breakers (trees planted in straight rows adjacent to cultivated lands) slow speed of wind down / less erosion during the dry season

6. Droughts & seasonal rainfall
· Seasonal rainfall can be identified if a topographic maps shows a lot of –

• Non-perennial streams
• Windmills
• Reservoirs
• Dams
• Canals

· Above features indicate the need to store water for dry season

7. Types of rain
· Convectional rain – over interior of South Africa
· Relief / orographic rain – mountain areas
· Cyclonic rain – along the SW Cape and Southern Cape