A base map is a map which shows the existing physical pattern of the land upon which survey info analysis or planning proposal can be superimposed. The information required for base map varies from map to map because it largely depends upon its scale, the area covered and the level of planning details. The base map, with its corresponding representation of the topography of the territory, shows the physical reality of the area where the new city plan is to be implemented. This physical reality is expressed through cartography, an absolutely essential component and probably the most important of all those comprising the information necessary for carrying out urban planning.
A base map is the graphic representation at a specified scale of selected fundamental map information; used as a framework upon which additional data of a specialized nature may be compiled. Within the multipurpose cadastre, the base map provides a primary medium by which the locations of cadastral parcels can be related to the geodetic reference framework; to major natural and man-made features such as bodies of water. roads, buildings, and fences; and to municipal and political boundaries. The base map also provides the means by which all land related information may be related graphically to cadastral parcels. Details to be shown on different level of base map:
For different levels of maps, information in base map is different.
1) For Regional Level Base Map
- Boundary The boundaries that can be shown at this level are national boundary, state boundaries, district boundaries, Taluk boundaries and village boundaries.
- Road National highway, state highway, major district roads, other district roads and fair weather roads.
- Railway lines Broad gauge and meter gauge lines, bridges are also to be included.
- Topography The major forestland, major hilly areas, rivers and streams, lakes, swamps, marshy lands etc.
- Settlements The urban settlements, rural settlements and important headquarters.
- Contours The contour interval in the base map at the regional level is 100m.
2) For City Level Base Map
- Planning and administrative boundaries Planning area boundary (if identified), metropolitan boundary, urban area boundary, municipal corporation boundaries and zonal boundaries, census ward, administrative sub-division limits (if any), urban village or rural settlement within the municipal limits or on the fringe of the municipal boundary, cantonment area boundary (if any), grids (artificial or latitudes and longitudes).
- Roads National highways, state highways, major district roads, arterial road, sub arterial road, collector roads, and local roads.
- Topography Hills, water bodies, Rivers and streams, canals, lakes, swamps, marshy lands etc.
- Religious places Religious places such as temples, mosques, churches, and tombs are shown.
- Contours The contour interval shown in the base map at this level generally ranges between 3m to 5m depending upon physiography of town and scale of map.
- Apart from these, all major places of archeological interests, public and semi-public building (important landmark), major agricultural and city forest, district parks, gardens, green belts, floodable areas, Utilities and services lines are also shown in the base map at this level.
3) The Site Planning Level Base Map
- All accesses to the site
- Vegetation such as trees, bushes etc.
- Water bodies
- High tension lines, overhead electric lines, water supply lines including hydrants, sluice valve, sewer lines including man-holes, vent pipes etc. with slope diameter of lines.
- Already existing features like well, brick kilns, quarries etc.
- Contours are drawn at an interval of 500mm.
Base Map Features
Before taking up any urban development plan exercise the first task, both from planning point of view and as statutory requirement, is to prepare or obtain reliable, accurate and up‐to‐date base map for the respective town or city for which the plan is being prepared. The amount of information to be represented on the map varies from map to map because information depiction depends on:
- Purpose of map
- Scale
- Projection
- Method of map‐making
- Draughting skill
Uniformity of base map with regard to presentation of features, scale, size and notations, facilitates the readability of these maps and comparison of one map with another. Mapping software of Remote Sensing and Geographical Information System are capable of generating maps with uniformity as well as processing data from different platform.
