Volume 6 – Geotechnical Manual, Site Investigation and Engineering ...

Chapter 4 REFERENCES ON GEOMATICS AND LAND SURVEY SERVICES
c. Control - The organization and control of the survey is simplified as the bulk of the surveyors
are working in good stable conditions at base, where they can be easily administered and
supervised. Those conditions produce high output and quality of work.
d. Supply - Supply is also simplified as in most cases the aircraft can operate from a commercial
airport. Any necessary special equipment such as GPS enabled digital camera can be carried
in the survey aircraft to the area of operations.
e. Weather - Although low cloud and extensive cloud-cover will prevent photography, only a
short time is needed to obtain suitable images. The weather is therefore seldom a major
problem, and once the photographic data has been obtained the survey is unaffected by
weather conditions.
4.14.1 Limitation of Air Survey
Survey Control - In order to relate an air-survey to the area in which the images were taken, it is
necessary to have precise ground coordinates, both plan and height, of points that can be clearly
seen on the images and on the ground. Coordinates and a clear description of each point are
provided by the ground surveyors as control for the aerial survey. Whilst aerial triangulation using
electronic computers provides a means of distributing additional controls on photographs a certain
amount of ground control is necessary, and must be provided before the air survey mapping works
can be commenced. Invert levels below the water surface cannot be ascertained.
Check - A field check of an air survey is necessary to eliminate errors due to misinterpretation of
detail. If the survey is at a large scale, completion of hidden detail (under trees, in shadow, etc)
may be needed. In all cases, names and description must be obtained from ground survey works.
Administrative work include:-
a. Arrangement for tasking of aircraft
b. Application for security clearance and the obtaining of the permit to fly aerial photographic
mission
c. Mobilization of personnel and equipments
4.15 HYDROGRAPHIC SURVEY FOR TERRITORIAL WATERS AND INLAND WATER
BODIES (JADUAL 2001 ITEM 14 PART V)
Hydrographic survey provides information and data to support:-
a. The management of coastal zones
b. The hydrographic survey of deltaic regions and river months up to two kilometers upstream
of river mouth
c. The development of coastal engineering, property, infrastructure projects and activities
d. The management and development of jetties, ports, harbors and associated maritime
facilities
e. The management and development along inland waterways and inland water body
March 2009 4-7