To build a new city or Township, surveying is to be done by considering all development works necessary for the city. The development works like street roads, property boundaries, water and sanitary pipes location, electrical lines, telephone lines etc. are involved in the city surveying.
Surveying Maps for a Township
Proper maps should be prepared for each of the systems of the city during surveying such as:
- Topographic map
- Street map
- Property map
- Water supply and sanitary map
- Electrification map
- Telephone line map
Each map should be prepared in such a way that a person can easily locate the required point in the map. Surveying is conducted for each system by their concerned departments or authorities.
Instruments for Surveying City or Township
Before discussing the preparation of maps, we must know the instruments used to conduct city surveying and they are
- Transit theodolite with tripod
- Leveling instrument with tripod
- Plane table instruments
- Leveling staff
- Ranging rods, pegs, optical square, arrows etc.
- Metric chain
- Metallic tape
- Invar tape
Preparation of Different Maps for a City
Topographic Map Preparation
In the preparation of topographic map, the whole area on which a township is going to build is divided into number of sectors. Each sector is enclosed by a polygon which are having a connection on common sides. In each sector, closed traversing is conducted using theodolite.
Plane table surveying is conducted in each sector and interior details like roads, parks, lakes etc. are located in the map. On the whole area some important points or constant points are noted and reduced levels (RL’s) are arranged at that points.
This is done by Fly leveling method. If there are any depressed areas like valley’s, lakes and high-rise areas like hills etc. then contour survey is conducted using tachometer method or plane table method.
In the map, the nature of ground is indicated by different markings or colorings or hatchings etc. Finally maps of all sectors are bring together to make it as a one map which gives the topographic details of whole city area.
Street Map Preparation
Preparation of street map is very similar to topographic map preparation but in this case the map is prepared with large scale as compared to the scale of topographic map. In this case also, the whole city area is split into number of parts and each part is surveyed using plane table.
In each sector map, the details of each street, name of street, road networks joining streets, name of the roads etc. are mentioned. Benchmarks are located at various points along the streets for future references using fly leveling.
Property Map Preparation
The property map is a large-scale map in which the boundaries of public properties and private properties are established. The boundaries are surveyed using plane table surveying.
After fixing boundaries the area is marked with plot numbers, premises numbers etc. in the map. By studying the property map, one can know about the boundaries of a particular area.
Here also the plane table surveying is carried out by dividing the whole area into parts.
Water Supply and Sanitary Map Preparation
Generally, water supply pipes or sanitary pipes are located in the underground. The whole water pipes network is to be prepared into a map.
These pipes are represented by conventional lines in the map and for easy location of pipe lines, water supply and sanitary map is prepared on the street maps.
Then one can easily locate the required point of water supply at any street or house. In this lines, some important locations like inlets, outlets, purification points, valves, manholes, inspection chamber etc. are represented by specific symbols.
Electrification Map Preparation
In a city, the network of Electrical lines also laid in the underground. So, they are also located in street maps and represented by conventional lines.
To differ the electrical cables from the water supply or sanitary lines different colored lines are used and representation of each colored line is described in the map. In some areas, the electric cable network is arranged in the air using concrete columns or poles.
In this case also, conventional lines are used to represent electric cables. But their location is to be described. Important points like supply point, transformer location etc. should show in the map with specific symbols.
Telephone Line Map Preparation
As similar to the water supply lines and electric lines, telephone cable lines are also laid in the underground so, that they also located in the street map using different colored conventional lines in the map. Important points are represented with specific symbols.
After preparing all the above maps, they are submitted to the development authority of the city and it will join with concerned departments and they will take the responsibility to build the city according to the map prepared. The concerned departments are municipality, electricity board, telecommunication departments etc.