Homesurveying and levellingWHAT IS CITY SURVEYING
WHAT IS CITY SURVEYING
UPENDRA KUMAR August 02, 2020
The city surveying is the branch of surveying. By the term, city surveying is meant an extensive co-ordinated survey of the area within the limits of a municipally made for the purposes. City surveying is valuable when large scale improvements or extension of the existing street systems, water supply, and sewer systems, layout and construction of new roads, development of the area in or near a city.
The city survey also valuable for new city planning.
PURPOSES OF THE CITY SURVEYING.
i. Making Maps
ii. Laying out plots and new streets.
iii. Constructing Streets, Pipelines, Sewers, buildings.
iv. Establishing reference points and benchmarks.
v. Locating property lines.
vi. Topographic Survey of the land.
INSTRUMENT REQUIRED FOR CONDUCTING CITY SURVEY
The following instrument required for the city survey.
1. Transit theodolite withstand.
2. Leveling instrument withstand.
3.Leveling staff.
4.Metallic tape.
5.Invar tape.
6.Plane table with accessories.
7. Ranging rod, optical square, pegs, etc.
In the city surveying, a high degree of accuracy is required, because of the high value of land in an urban area. There are two types of control in the city surveying.
1. HORIZONTAL CONTROL: The primary control stations are established by triangulation, precise traversing& secondary control stations running transit and tape traverse of the desired precision connecting the triangulation stations. The secondary control is established by running transit and tape traverses of the desired precision connecting the triangulation stations. Triangulation for a city survey the sides are necessarily shorter in length, and an object such as church spires, flag poles, tops of hills, chimneys, high buildings, water tanks, etc . are generally used as triangulation stations in order to form well-shaped triangles. The angles measure between stations cannot be determined by direct measurement, they are obtained by reduction of the center. The triangulation system consists of either quadrilaterals or polygons with a central station. Astronomical observations for azimuth should be made at two or more stations. All reference points are plotted by means of plane rectangular co-ordinates with reference to these axes.
2. Vertical Control:-The next step is to establish vertical control. The purpose of vertical control is to establish benchmarks at convenient all over the area. The first -order benchmarks are established by precise leveling on permanent objects. Additional benchmarks are established at traverse stations, and also on permanent objects.
Preparation of street map
It is prepared on a large scale and to show the network of the street, road, park with names.
The township area is divided into different sections. The street map of each sector is prepared by the plane table. The fly leveling did along the street and fixed the benchmark for future use.
Preparation of Topographic map
The entire survey area is divided into a number of sectors, each of which is enclosed by a polygon. The survey used in the preparation of topographic surveys by closed traverses by traversing methods.
The map is drawn to a scale of 1 in 2000 and is divided into sheets. The interior details are located by the plane table. The fly leveling is used for RLs of important points. Contouring is done by plane table or techeometre.
TOPOGRAPHICAL MAP
Preparation of property map
The property map is usually drawn to a scale of 1 in 500 and is divided into sheets. It shows
the length and bearings of all street lines, lane lines, and all details.
Preparation of underground map
The underground map is drawn to a scale of 1:500. In this map shown streets, lawn, benchmark, surface structure, telephone line, electric line, trees, sewers, water pipe, gas line, and other utilities in different colors and different symbols.
The traverse lines are run as long as possible and as nearly as possible on the center of the streets by fixing stations at the junctions of all principle streets.SEE ALSO: Method Of Traversing In Surveying