Map scale
The ratio between the distance covered on a map and the actual distance covered on the earth.
Small-scale map: features look small, the ground area covered is large, and few details are shown.
Large-scale map: features look large, the ground area covered is small, and many details are shown .
1:24,000 > 1: 100,000
Topographic map symbols (refer to Figure E.25, page 322-323 for more details)
Thickness: Index contour line> intermediate contour line>supplementary contour line
Depression: contours are hachured or closed contour with hatch (hachure) marks drawn toward the center of the depression.
High spots: closed contour line without hatch marks
Bathymetric contours: drawn in blue to show the depth of water bodies and do not follow the contour interval.
Bench mark: Designated with BM, x or △ , black permanent markers that generally have higher elevation.
Green shading: forest areas
Red shading: urban areas
Blue shading and blue lines: water
Black lines: political boundaries or roads
Red lines: survey lines
Brown line: contour lines
Purple feature: updated information
Elevation calculation:
Local relief=elevation of adjacent hills-elevation of adjacent valleys
Total relief=elevation of the highest point- elevation of the lowest elevation
Estimation of hill top/ridge top : Add half the contour interval to the elevation of inner-most contour line.
Estimation of the bottom of depression : Subtract half the contour interval from the elevation of inner-most contour line.
Contour line characteristics :
(1) Contour lines crossing rivers or valleys always bend upstream or up valley, creating ‘v’ form toward upstream (higher
elevation)
(2) Sparse and Large spaced contour line indicates gentle slope gradient and a flatter spot.
Converged and closed contour lines represent hills, mountains or high elevation spot.
Map distance calculation
Convert the map distance to earth distance:
X mile=
X inch=
4 in
map
map
1 map x
24,000 in
1 in
1 ft
12 in
1 mi map x x
5280 ft
4 in
1 x
24,000
1 in map in x
1 ft
12 in

 elevation
Gradient=
Distance
Steps to calculate slope gradient:
(1) Determine the change in elevation between two points
(2) Calculate the distance separating these two points by converting the map distance to the earth distance
(3) Calculate the gradient by dividing the change in elevation by the distance (unit: ft/mi)
Relation between gradient and contour line spacing:
The closer the contour line, the steeper the gradient.
The farther apart the contour lines, the gentler the gradient.
Topographic profile
Topographic profile: helps to visualize the relief of the landscape
Step of drawing pressure profile: (refer to page 292-293 of lab manual for more details)
(1) Pick two points on the map and connect them with a straight line.
(2) Fold the paper along the line, overlap isoline in one piece of paper with the horizontal axis of profile on another paper,
and make a tick mark on the horizontal axis.
(3) Carefully mark the intervals on horizontal axis and label them with appropriate value according to the contour lines
(4) Set up the vertical axis, which does not necessarily start at zero and may start from the lowest isoline value.
(5) Plot the points correctly in the coordinate according to their actual pressure and position, and connect them with a
smooth line.
Vertical exaggeration (VE)
Vertical exaggeration: the ratio between vertical scale and horizontal scale on the topographic map.
Steps for determining vertical exaggeration:
(1) Determine the map scale
(2) Convert the units on the right side of the representative fraction to either feet or meters
(3) Determine the vertical exaggeration
(4) Simplify the vertical exaggeration (e.g. 10X V.E. 20X V.E.)
The higher the vertical exaggeration, the steeper the landscape.
Profiles with the same vertical exaggeration are needed when comparing landscape.
Purpose of topographic map land-use management, show landform details, overview landscape, or tour map (limited information)