GGR272H5 Lecture Notes - Lecture 7: Cartographic Generalization, Granularity
GGR272 Monday 12th Nov
Scale, data resolution,
Contents
• Geographic vs cartographic scale
• Data resolution
• Cartographic generalization
Scale defined
• Geography
- Scale is synonymous with extent of study area
- Large scale means large area, e.g. Global
• Cartography
- Scale equals representative fraction (RF)
- Large scale means large RF
- Large scale map covers a small area
→ Mapped items are large
Representative fraction
• Representative fraction is the ratio of a distance unit on the map to the same
distance unit on the ground
Map scale
• Most maps have RFs between 1:1,000,000 and 1:1,000, e.g.
- 1cm on map = 1,000 cm (10 m) on ground, or
- 1 inch on map = 1,000 inches ground, etc.
• Electronic maps
- Scale based on display or printed size
Large vs small scale
Data resolution
• Granularity of data
• Resolution of remote sensing images, e.g. 60m/30m or 1m pixel sizes
• Resolution of census data by levels of census geography, e.g. DA or CT
• Other enumeration units, such s city of Toronto neighborhoods
Canadian census geography
Us census geography
Cartographic generalization
• The process of reducing information content of maps
Document Summary
Contents: geographic vs cartographic scale, data resolution, cartographic generalization. Scale is synonymous with extent of study area. Large scale means large area, e. g. global: cartography. Large scale map covers a small area. Representative fraction: representative fraction is the ratio of a distance unit on the map to the same distance unit on the ground. Map scale: most maps have rfs between 1:1,000,000 and 1:1,000, e. g. - 1cm on map = 1,000 cm (10 m) on ground, or. 1 inch on map = 1,000 inches ground, etc: electronic maps. Scale based on display or printed size. Data resolution: granularity of data, resolution of remote sensing images, e. g. 60m/30m or 1m pixel sizes, resolution of census data by levels of census geography, e. g. da or ct, other enumeration units, such s city of toronto neighborhoods. Cartographic generalization: the process of reducing information content of maps.
