(Highway Surveys Plans and Road Materials)
RECONNAISSANCE SURVEY
The second stage of surveys for highway location is the
reconnaissance to examine the general character of the area for deciding the
most feasible
routes for detailed studies. A field survey party may inspect a fairly broad stretch of land along the
proposed alternative routes of the map in the field. All relevant details not
available in the map are collected and noted down. Some of the details to be
collected during reconnaissance are given below:
(i)
Valleys, ponds, lakes, marshy
land, ridge, hills, permanent structures and other obstruction along the route
which are not available in the map.
(ii)
Approximate values of gradient,
length of gradients and radius of curves of alternate alignments.
(iii)
Number and type of cross drainage
structures, maximum flood level and natural ground water level along the
probable routes.
(iv)
Soil type along the routes from
field identification tests and observation of geological features.
(v)
Sources of construction materials,
water and location of stone quarries.
(vi)
When the road passes through hilly
or mountainous terrain, additional data regarding the geological formation,
type of rocks, dip of strata, seepage flow etc.
PRELIMINARY SURVEY
The main objectives of the preliminary survey are:
(i)
To survey the various alternate
alignments after the reconnaissance and to collect all the necessary physical
information and details of topography, drainage and soil.
(ii)
To compare the different proposals
in view of the requirements of a good alignment.
(iii)
To estimate quantity of each work
materials and other construction aspects and to work out the cost of alternate
proposals.
(iv)
To finalize the best alignment
from all considerations.
(v)
The preliminary survey is carried
out to collect all the physical information which is necessary in connection
with the proposed highway alignment.
LOCATION SURVEY
The centre line of the road finalized in the drawings
is to be translated on the ground during the location survey. This is done
using a transit theodolite and by the staking of the centre line. The location
of the centre line should follow, as closely as practicable, the alignment
finalized after the preliminary surveys. The centre line stakes are driven at
suitable intervals; say at 50metre intervals in plain and rolling terrains and
at 20metre in hilly terrain.