Field surveys involve collecting data directly from the field, such as through interviews, observations, and measurements. This data is considered primary because it is collected firsthand and is not derived from other sources.

The National Population Register (NPR) is a register of all usual residents of India. The primary source of data for the NPR is the Census data, which is collected every 10 years.

Secondary sources of data are those that have been derived from other sources. Census data, for example, is collected through field surveys and then processed and analyzed to create statistical reports and maps.

Satellite imagery is the primary source of data for the Land Use Land Cover (LULC) maps of India. Satellite images provide detailed information about the Earth's surface, including land cover types, vegetation, and water bodies.

Topographic maps are created using a variety of data sources, including aerial photographs, satellite imagery, and field surveys. Aerial photographs provide detailed information about the Earth's surface, while satellite imagery provides a broader view. Field surveys are used to collect data on specific features, such as elevation and vegetation.

The primary source of data for the National Water Resources Information System (NWRIS) in India is hydrological data. Hydrological data includes information about precipitation, runoff, and groundwater levels.

Soil maps are created using a variety of data sources, including satellite imagery, topographic maps, and field surveys. Satellite imagery provides information about the Earth's surface, while topographic maps provide information about elevation and slope. Field surveys are used to collect data on soil properties, such as texture, structure, and pH.

The primary source of data for the National Forest Inventory (NFI) in India is field surveys. Field surveys are conducted to collect data on forest area, tree species composition, and forest health.

Land use maps are created using a variety of data sources, including satellite imagery, topographic maps, and field surveys. Satellite imagery provides information about the Earth's surface, while topographic maps provide information about elevation and slope. Field surveys are used to collect data on land use types, such as agriculture, forestry, and urban development.

The National Atlas of India is created using a variety of data sources, including satellite imagery, topographic maps, and field surveys. Satellite imagery provides information about the Earth's surface, while topographic maps provide information about elevation and slope. Field surveys are used to collect data on specific features, such as land use and population distribution.

Geological maps are created using a variety of data sources, including satellite imagery, topographic maps, and field surveys. Satellite imagery provides information about the Earth's surface, while topographic maps provide information about elevation and slope. Field surveys are used to collect data on rock types, structures, and fossils.

The primary source of data for the National Mineral Inventory (NMI) in India is mineral exploration data. Mineral exploration data includes information about the location, size, and quality of mineral deposits.

Climate maps are created using meteorological data, which includes information about temperature, precipitation, and wind. Meteorological data is collected from weather stations and satellites.

The primary source of data for the National Biodiversity Information System (NBIS) in India is biodiversity data. Biodiversity data includes information about species distribution, abundance, and habitat.

Environmental impact assessment (EIA) reports are created using a variety of data sources, including satellite imagery, topographic maps, and field surveys. Satellite imagery provides information about the Earth's surface, while topographic maps provide information about elevation and slope. Field surveys are used to collect data on specific environmental features, such as water quality and air quality.