Chapter 6: Relief Portrayal
The terrain surface provides the foundation upon which we play out our lives. Nothing in the environment is
immune from the vertical differences on the earth’s surface that we call relief.
In mapping, a terrain surface is a threedimensional representation of data about the elevations of our physical
environment, and cartographers use relief portrayal to map those data.
Planimetric maps are useful when the mapped area is essentially flat or when facts about an area’s relief aren’t
important to your needs. So, these kinds of maps ignore relief.
However, if relief information is important, it’s best to look at topographic and other maps that show the three
dimensional nature of the terrain surface.
There are 2 ways of relief portrayal; absolute relief mapping, and relative relief mapping.
Absolute Relief Mapping Methods
Absolute relief is the actual elevation values at locations in the landscape. Absolute relief methods
provide the numerical elevation and water depth information.
Spot elevations, benchmarks, and soundings
On topographic maps, engineering plans, and/or aeronautical charts, the elevation of the surface
is given numerically at individual survey points. These elevation values, relative to the mean sea
level are called spot elevations.
Searching for survey marks, or benchmarks at road intersections or forks are much easier than
at changeable location such as stream merging.
Water depth readings are called soundings. For thousands of years, mariners used lead lines to
measure depth but now we have electronic depth measuring instruments. Sounding values are not
relative to mean sea level but they’re relative to specific definitions of low water.
Contours are lines of equal elevation above a datum. It’s common to use contours in topographic
maps to show variations in relief. The vertical distance between contours are called the contour
Isobaths, also called depth contours or depth curves, are lines of equal water depth below the
mean sea level. They’re found on nautical charts.
Hypsometric tinting (also called hypsometric coloring) is a method of “coloring between
contour lines” that enhances the relative relief cues for contours while maintaining the absolute
portrayal of relief. Some isobaths have a stepped appearance much like a layer cake. This is because the space
between contours is given a distinct gray tone or color, called a discrete hypsometric.
With newer technologies, the abrupt change between hypsometric tints can be minimized by
gradually merging one tint into the next, giving a smooth appearance to tonal gradation and this
is called continuous hypsometric tinting.
Relative Relief Mapping Methods
In our daily lives, we’re usually concerned with the local range between high and low heights, or the
relative relief, rather than the absolute elevation values.
Planimetric perspective maps
These maps represent only the horizontal positions of features and not the vertical positions that
topographic maps show. Planimetric perspective maps give an overhead view of the mapped
Raised relief globes: Since globes present the truest picture of the earth as a whole, raised relief
globes provide the most realistic and useful portrayal of the vertical dimension. However there is
a flaw, when we reduce the size of earth to a bowling ball, earth would be smoother than the ball.
That’s why we use vertical exaggeration, which happens when the vertical scale is larger than the
Relief models: We can also minimize the problem of high vertical distortion by using physical
relief models rather than globes. Relief models are constructed to show the curvature of the
Raised relief topographic maps: It’s made by taking a flat topographic map, printing on a sheet
of plastic, and using heat to vacuumform it into a threedimensional model. But they also have
flaws because of their shortcoming such as; cost more, difficult to store and displacement of
features is also common.
Hachures: This was common on nineteenth century smallscale maps and they look like
caterpillars crawling across the map. They were trying to show the terrain with a really basic and
Relief shading: Relief shading has been used on maps since the late nineteenth century to
enhance the threedimensional appearance of terrain features. The principle unde