Introduction of Township Survey
A project on township or city surveying involves proper coordination of all types of development work necessary for the township or city. It entails the implementation of the following systems:
- Street system
- Property lines
- Water supply system
- Sanitary system
- Electrification system
- Telephone system
In the case of a newly developing township or the modification of one in existence for some time, a plan for development should be clearly worked out so that the facilities provided in the master plan may be suitably extended.
A project survey for the township should be conducted in order to prepare maps in respect of the following:
- Street survey
- Property demarcation
- Water supply
- Sanitary system
- Electrification system
- Telephone system
The procedure for preparing these maps is described later. All the surveys are conducted by the development authority of the city or town, in coordination with concerned departments like the Roads Department, Municipality or Corporation, Electric Supply Department, Telephone Department, etc.
Survey townships are generally referred to by a number based on the Public Land Survey System (PLSS). A reference to the township will look something like “Township 2 North Range 3 East”, or “T2N, R3E” and such a notation is used in property descriptions based on the PLSS. Townships were originally surveyed and platted by the United States General Land Office, using contracted private survey crews, and are marked on the United States Geological Survey maps of the United States.
Townships are normally a square approximately six miles (9.7 km) on a side with cardinal boundaries conforming to meridians and parallels, containing 36 sections of one square mile (2.6 km2) each. The northern and westernmost tier of sections in each township is designed to take up the convergence of the east and west township boundary lines or range lines, as well as any error in the survey measurements, and therefore these sections vary slightly from being one square mile or 640 acres (260 ha). Survey townships exist in some form in most states other than the original 13 colonies, Kentucky, Tennessee, Vermont, and Maine.[dubious – discuss] Irregular or fractional townships with fewer than a full 36 sections are created where full townships cannot be laid out due to existing senior boundaries, such as Spanish/Mexican ranchos, Indian reservations, state boundary lines, etc.
This kind of township is similar to geographic townships in the province of Ontario, Canada.
In Kentucky, the Jackson Purchase (the area west of the Tennessee River) is divided into townships and ranges. In Tennessee, the entire state is surveyed into townships and ranges that make up 13 survey districts of the Tennessee State Survey. In extreme northern Maine, there is an area divided into townships and ranges oriented to true north. A region in the central part of the state, made up of 17 surveys, is divided into townships, but these are not oriented to true north. The remainder of the state is on metes and bounds. Similarly, Vermont and New Hampshire are mostly metes-and-bounds states but have areas in the north that are surveyed into townships not oriented to true north. Most of Ohio is surveyed using the Public Land Survey System, but several sizable areas are metes-and-bounds, including the Virginia Military Reserve, Donation Tract, French Grant, and the three Moravian grants (Gnadenhutten, Schoenbrunn and Salem). A 150,000-acre (61,000 ha) area in southern Indiana (Clark’s Grant) is not surveyed into townships but is still a gridded survey. Portions of the Texas State Survey use square townships. Sizeable portions of Alaska, Arizona, California, Idaho, Montana, Oregon, and Washington, are unsurvey. Substantial swampy areas in Florida and Louisiana are also unsurveyed.
Both New York and Pennsylvania have metes-and-bounds surveys, but in the western parts of these states, the metes-and-bounds form square townships many of which are also civil townships. Besides these, nearly every state has areas of metes-and-bounds that were never included in the grids (like along major rivers) or were removed from the grid, usually due to surveying mistakes.
Instruments Required for Conducting City Survey
The following instruments are required for conducting a city survey
- Total station with stand
- Leveling instrument with stand
- Leveling staff
- Metallic tape
- Invar tape
Preparation of Topographic Map
The entire area is divided into a number of sectors, each of which is enclosed by a polygon. The polygons are connected by common sides. They are treated as closed traverse and the traversing is done by total station. The interior details are located by plane table or the transit-and tape-method. These details include houses, roads, lakes, parks, railway lines, stations, etc.
Fly leveling is undertaken to establish the RLs of important points and benchmarks. Contouring is done by plane table or tacheometer. The nature of the ground surface is indicated in relief (i.e. coloring, shading, hatching, etc.) on the map.
Finally, all the sectors are assembled in one map so that the township area or city area.
Preparation of Street Map
The street map is prepared using a large scale to show distinctly the network of streets, roads, lanes, parks, etc. Names of streets, roads, and parks should be mentioned. In this case, also the township area is divided into different sectors. The street map of each sector is prepared by a plane table. In such a map the location of interior details (i.e. lakes, houses, and other properties) need not be shown. Fly leveling is done along the streets and benchmarks are established at different points for future reference.
Preparation of Property Map
This map is also prepared using a large scale to show the boundaries of public and private properties, plot numbers, premises numbers, and so on. The property map is also prepared by plane table by dividing the total township area into different
Preparation of Water Supply and Sanitary Map
The network of the water supply distribution system and that of sewer lines are laid underground. So, to facilitate the location of any spot from the top, the entire networks of the water supply and sanitary works are shown by conventional lines on the street survey map. All the essential lines and points (such as intake points, purification point, check valves, fire hydrants, manholes, lamp holes, inspection chambers, etc,) are marked with specific symbols. Preparation of Electrification Map:-
Generally, the network of cables for electrification of the township or city is also Laid underground. Therefore, the methods of distribution should be marked on the street survey map using a different color convention or by suitable symbols. The specific points of the supply line should be clearly marked to aid the easy location of any spot incase of the cable fault. The network of the supply system should be indicated on the street survey map even if the electrification is through overhead lines.
Preparation of Telephone Map:-
The network of telephone cables also lies under the ground. So, to aid the location of a fault, the network system is shown on the street survey map using a certain color convention or by suitable symbols.
Coordination Work for Township Survey
The development authority of the city or town is responsible for the construction of streets, roads, culverts, bridges, flyovers, bypasses, subways, parks, public places, etc. The sanitary and water supply system is implemented by the municipality or corporation. The electrification program is carried out by the state electricity board, and the telecommunication system is run by the telegraph department.