Engineering Survey

1. RANGING

2.  Method of locating or establishing intermediate points on a
straight line between two fixed point or two survey stations is
called as ranging.
There are two methods of ranging
Direct Method (Two ends of survey line or stations are inter-visible)
 Indirect Method (Two ends of survey line or stations are not inter-
visible)

4. DIRECT METHOD
 This method is used when two ends of survey stations or survey lines are
inter-visible.
 Direct ranging can be done by 2 methods:

5.  1) RANGING BY EYE: Consider two pints X and Y which are inter-visible to
each other. In this method ranging rod is fixed at station X and Y. Suppose if
we want to locate a point Z on ground which is in line with XY. The surveyor
stands half a metre back side of ranging rod at X in line with XY. Assistant
then moves another ranging rod under the guidance of surveyor in such a
way that ranging rod hold by assistant is in the line XY at point Z betwwen X
AND Y. Similarly other points can be located by similar way. Surveyor has to
guide assistant by using some hand signals so that ranging rod comes in the
line.

7. Indirect Ranging
 This method is used when two ends of survey stations or survey line are not
inter-visible. when the end of the line are nt distinctly visible from one another
due to distance being too great ,then indirect ranging can be adopted.
 Various obstructions such as pond, hills and buildings come across in chaining
process.

8. OBSTACLES IN CHAINING
 While performing chain survey operations in the field, a surveyor may come across various
kinds of obstacles such as ponds, rivers, buildings, woods, spurs, etc. which obstruct ranging
and / or chaining along the survey lines. In order to continue chaining, special methods
(based on simple geometrical or trigonometrical principles) are used for measuring distances
across such obstacles,
 Some typical cases of various categories are discussed below.
 1.where obstacles can be chained across but not seen across, i.e. chaining free, vision
obstructed-
 Examples of such obstacles are an intervening hill, rising ground or wooded field with trees
or brushwood,

9.  2. Where obstacles can be seen across but not chained across, i.e. chaining obstructed but
ranging free. Typical example of this kind of obstacle is a deep stream, canal or a river.
 3. Where obstacles can neither be seen across nor chained across, i.e. both ranging and
chaining obstructed. But can be chained around. Typical example of such obstacles is
buildings and spurs. Following methods may be employed to overcome the obstacles.
 4.Where obstacles can be seen across and chained around, but cannot be chained across, i.e.
vision free but chaining obstructed. Examples of this of obstacle are a pond, a lake or a tank,
etc. some of the methods that can be employed are described below