FORM FIVE SELECTIONS 2021** FORM 5 JOINING INSTRUCTIONS
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Introduction
Geomorphological
map is a map record of information on surface form, materials (soil and rock),
surface processes and in some cases the age of the landforms. It provides a
basis for terrain assessment. The mapping involves field documentation of the
terrain with the assistance of the remote sensing facilities. In the context of
environmental management, the geomorphological mapping enables the
geomorphologist to obtain a better understanding of the landscape before giving
advice. It provides a map record of the landscape characteristics relevant to
the project in hand. In addition, it provides an essential basis for derivative
and special purpose maps.
Aspects
considered before starting mapping
● Scale and legend
● What should be mapped
● Availability of base maps at the required
scale
● Accessibility of the area to be mapped
● How the
final map is to be reproduced: Whether the map is to be printed and published
in large quantities or as small number of working documents
● Need for the
map to provide comprehensive or selective statement of the geomorphology
Scale
Selection of a scale depends on the details needed, purpose of the map,
complexity and the dimensions of features that need to be documented. The scale
to be used is normally decided by a person doing the mapping. It should be
large enough to show all necessary detail but small enough to avoid an
excessive number of map sheets. It also depends on the type of available
remotely sensed imagery. The scale is very important to communicate the
appropriate level of detail for the intended use. The presentation scale should
be dependent upon the actual scale of mapping and the methods and intensity of
field checking -- sometimes referred to as the Terrain Survey Intensity Level
(TSIL). As the scale become smaller, larger and larger areas are shown on the
same size of map sheet. In smaller
scaled maps most details are generalized and others eliminated. The details of
the information mapped depend on the scale used.
Categories of mapping scales as modified from
Van Westen (1993):
Synoptic
or territorial scale maps (>1:50,000) are often process
inventory maps, used by planning agencies to direct
allocation of funds, develop emergency preparedness
plans and similar tasks. An example is the overview map of the United States
produced at a scale of 1:7,500,000.
Medium
scale maps (1:20,000 to 1:50,000) are generally used for preliminary or
regional hazard assessments and feasibility studies, to be followed by more
detailed work.
Large-scale
maps (1:5,000 to 1:20,000) are generally used for planning of land use in
urban areas or resource development in rural areas. Depending on the use,
large-scale maps quite often must be supplemented by detailed site
investigations or on site assessments
Detailed
scale maps (1:5,000 to 1:500) are for site development, monitoring and
management problems. It covers hazard assessment of a specific site and should
be accurate enough to guide layout of individual structures or specific
operations, or to plan mitigation. Engineering plans at these scales can also be
used to derive design parameters.
Legend
The legend is the key to the map and shows how its
content is organized. To find out what a map symbol stands for, look at the
legend. The legend is a list of symbols used on a map, indicated by a sample
symbol with an explanation showing what feature that each depicts. Each symbol
should appear in the legend exactly as it looks on the map. It should be as
clear and comprehensive as possible and with a minimum of complication. Symbols
allow a map to show lots of information in a small space. By using symbols,
maps can have more content and less clutter. The geomorphological symbols used
are variables. There are no unified schemes. The symbols used vary from one
country to another (Figure 7.1).
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