Introduction to Geological Map Interpretation
I. Components of a map
A map is a scaled-down, two-dimensional representation of a specified area, showing
features of interest, e.g. road map, vegetation map, geological map. It consists of 3
components:
1. the map area, which contains the information of interest, and which is oriented with
respect to the rest of the Earth using latitude and longitude and/or a North arrow
(geographic information);
2. a scale, which tells us how much reality has been reduced / the size of the area being
shown on the map; and
3. a Key/Legend that explains the symbols on the map.
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,Scale
• The amount by which reality is reduced; thus, a
1:1 000 000 map scale means that reality has been
reduced by one million times, so 1 cm on the map is
equal to 1 000 000 cm (= 10 000 m; or 10 km) in reality
• Scale is shown as a Bar Scale or Ratio (Representative
fraction)
• A large scale map shows a smaller area in more detail
• Ratio scales are not useful if maps are enlarged or
shrunk electronically – only bar scales can be used
, Geographic location & orientation
• Compass bearing (azimuth) clockwise from North (000o – 360o)
• True vs Magnetic North
• Latitude/longitude
• GPS/Regional/local survey grids
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I. Components of a map
A map is a scaled-down, two-dimensional representation of a specified area, showing
features of interest, e.g. road map, vegetation map, geological map. It consists of 3
components:
1. the map area, which contains the information of interest, and which is oriented with
respect to the rest of the Earth using latitude and longitude and/or a North arrow
(geographic information);
2. a scale, which tells us how much reality has been reduced / the size of the area being
shown on the map; and
3. a Key/Legend that explains the symbols on the map.
prangesmile.com
,Scale
• The amount by which reality is reduced; thus, a
1:1 000 000 map scale means that reality has been
reduced by one million times, so 1 cm on the map is
equal to 1 000 000 cm (= 10 000 m; or 10 km) in reality
• Scale is shown as a Bar Scale or Ratio (Representative
fraction)
• A large scale map shows a smaller area in more detail
• Ratio scales are not useful if maps are enlarged or
shrunk electronically – only bar scales can be used
, Geographic location & orientation
• Compass bearing (azimuth) clockwise from North (000o – 360o)
• True vs Magnetic North
• Latitude/longitude
• GPS/Regional/local survey grids
wordpress.com
xmswiki.com
