Cartography – Maps & Scale YouTube Lecture Handout
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Agenda
- Data and its types
- Map and Scale
- Analyzing Maps
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Types of Data
Idiographic vs. Nomothetic
Map
- Map is graphical representation of real world.
- Art of map making = Cartography
- Maps can be:
- Reference or Base Maps: Show natural and human-made objects from geographical environment with an emphasis on location, atlas or topographic maps
- Thematic Maps: Geographical distribution of one phenomenon or spatial associations that occur between a number of phenomena
- Isopleth maps - Isolines connect points of equal magnitude.
- Choropleth map - tonal shadings are graduated to represent areal variations in number or density within a region, usually a formal region.
Topographic Map
Thematic Maps
- Quantitative:
- Choropleth: Color gradient
- Chorochromatic: Various Color
- Choroschematic: Symbols
- Isopleth: Lines
- Proportional Symbols: Size of symbols
- Dot Density Maps: Population
- Qualitative
Why We Need Maps?
- To represent a larger area than we can see
- To show a phenomenon or process that is not visible by eyes
- To present information concisely
- To show spatial relationships
How to Prepare Maps?
- By actual survey
- By photographs
- By free sketches
- By Computer Maps
Elements of Scale Map
- Symbols and a legend
- Scale
- Direction (indicated by the north arrow)
- Map grid or coordinate system
- About the map (date created, title, author, source information)
Characteristics of Map
Reading Map is Indeed an Art!
- Maps are selective views of reality
- Size of the map relative to reality (scale)
- What՚s on the map (symbolization)
- Shape of the map (projection)
Scale
- Scale is about distance.
- How long?
- How far?
- How wide?
- How far on the map and how far on the ground?
Map Scale
- Representative Fraction: Is a ratio like 1: 1000
- Verbal Statement: 1: 1,000, 000 verbally is “1 centimeter on the map equals 10 kilometers on the Earth՚s surface”
- Graphic Scale
1: 25,000 Scale
- 1 centimetre (cm) on map = 25,000 cm on the ground
- 1 cm on the map = 250 metres (m) on the ground
- 4 cm on the map = 1 kilometre (km) on the ground
Analyzing Map Scale
Types of Scale: Comparative Scale
Diagonal Scale
Vernier Scale
Time Scale
Reduction & Enlaargement
- After reducing a map from 1: 10,000 to 1: 50,000 scale, the new map is, the original line or scale & times the area.
- After enlarging a map from 1: 100,000 to 1: 20,000 scale, the new map is times the original line or scale & times the area of the original scale.
- If a map with scale 1: 100,000 is enlarged by 10 times the new scale can be calculated as follows. Assume that the new scale is , then, or , so & enlarged scale is .
Reduction/Enlargement by RF
- When the map is enlarged the RF is decreased. E. g. , if the original map with scale 10 cm = 5 km, is enlarged 4 times, the new RF will be 1: 12500
Maps Based on Scale
- Cadastral or Revenue Maps: Large scale 16 - 20 inches to 1 mile
- Topographical Maps: Single purpose, 1 in = 1 mile
- Wall Maps: Depict Large Area 1 in = 4 miles
- Atlas Maps: Small-scale chorographical, 1: 2000000
Map Symbols
- Symbols are a code instead of text
- Symbols can be
- Point: Each symbol count as one occurrence
- Qualitative: Explains location
- Quantitative: Shows distribution
- Line: One-dimensional for borders, roads etc.
- Area: two-dimensional like garden, plot etc.
- Point: Each symbol count as one occurrence
- Consider shape, size, orientation, pattern, color, value
✍ Manishika