This document discusses various methods used to represent physiographic features on topographical maps. It describes isopleths as lines connecting places of equal value, such as temperature or rainfall. Choropleths show how a measurement varies across a geographic area by shading or patterning areas proportionately. Specific representation methods covered include hachures, hill shading, contour lines, spot heights, and layer tinting.
3. Physiographic refers to the
difference in height between
the highest and lowest land
surface in a locality of nature.
Physiographic [or terrain] is
an essential aspect in physical
geology.
INTRODUCTION
6. Methods used to
represent features are
based on this two.
1.ISOPLETH,
2.CHOROPLETH.
TYPES OF METHODS TO
REPRESENT FEATURES ARE;
7. Isopleths are lines joining
places of equal value ,this value
may be in form of quantity ,
intensity or density.
Following are few examples of
isopleths,
1.ISOPLETH
8. 1. Isobar – Equal pressure,
2. Isotherms– Equal
temperature,
3. Isohyet – Equal rainfall,
4. Isohaline – Equal salinity.
Isopleth maps are also require
a large amount of data for
1.ISOPLETH
10. In this method areas are
shaded or patterned in
proportion to the
measurement of statistical
variable being displayed on
the map.
2.CHOROPLETH
11. The choropleth map
provides an easy way to
visualize how a measurement
varies across a geographic
area or it shows the level of
variable within a region.
2.CHOROPLETH
13. It is used to show surface features
on the map.
Hachures are short lines of varying
thickness to show the shape and slope
of land.
In accordance with this technique, the
steeper slope is represented by thicker
lines.
A. HACHURING
14. They do not represent exact
elevations but are mainly used to
show large rocky outcrops.
It is one type of isopleth method.
A. HACHURING
16. Hachuring was replaced with a
scientific form of hill shading and spot
heights.
Hill shading resembles a light and
shadow effect.
Valleys and the sides of mountains
appear as that they are cast in
shadow.
B. HILL SHADING
17. It is visually striking method.
However does not show height which
means that it is no more accurate like
contours.
It is a choropleth method.
B. HILL SHADING
19. Contour lines are lines that connect
points (spot height) that are the same
height reference to MSL.
They accurately depict the height,
shape, slope of a landscape.
The numbers which are featured on
each line represent the exact height
on the land at points along that lines.
C. CONTOUR LINES
20. The patterns created by the line show
the shape of the land.
The slope an also be identified by
using contour lines.
The closer contour lines represent the
steeper slope.
The gentle spaced contour lines
represent the gentle slopes.
C. CONTOUR LINES
21. Contour interval:
It is the difference in the height between
the contour lines.
Contour interval may be in 20m, 50m,
100m…
C. CONTOUR LINES
24. They are used to show the exact
height of the land at a particular
point.
They are depicted using a dot (or
triangle) and a corresponding number,
which represent altitude at that point.
They do not provide much
information about the shape of the
D. SPOT HEIGHT
26. Layer tinting uses different colors (or
shades) to represent different heights.
A different color is used for each band
of elevation.
Each shade of color or band represent
a definite elevation range.
E. LAYER TINTING
27. A legend is printed in map to indicate
the elevation range represented by
color.
However, this method does not allow
the map user to determine the exact
elevation of a specific point-only the
range.
E. LAYER TINTING