Data input refers to the procedure of automatization of the data and the conversion into forms that can be stored and analyzed in computers. This procedure is fundamental in every GIS and it differentiates depending on the model (vector or raster) and the origin of the data.
SOURCES OF GIS DATA
There are many sources of data available for Geographical Information System (GIS). Such sources include the following:
- Land surveying.
- Remote sensing.
- Map digitizing.
- Map scanning.
- Field investigation.
- Tabular data.
- Land Surveying: Land surveying is defined as the process by which measurement of land is made and then represent such measurement by tables, plans or layout for specific purposes. It can also mean the measuring and mapping out of the position, size and boundaries of an area of land.
- Remote Sensing: Remote consists of the main sources of digital data for input in a GIS. Remote Sensing (RS) provide useful tools for environmental and natural resources management. They are widely recognized as supporting and management of the appropriate utilization of resources at the country, regional and global levels. Through the use of remote sensing, employment opportunities are available in a wide range of areas; including agriculture, forestry, coastal development and management, urban planning and development, medical technology, mapping and planning, disaster mitigation and environmental management.
- Map Digitizing: Map digitizing involves the extraction of data values from graph e.g. in most scientific publication only plots but no data values are published. Map digitizing involves a three step process:
- Import the graph from a file or copy it over the clipboard.
- Define the axes system.
- Digitize it automatically or manually.
- Map Scanning: Another commonly used method for data input is scanning. Existing maps of various scales containing different type of information about the area of interest in small or big detail. These maps can be scanned, thus the information of these maps can be fed into a GIS and be integrated with other existing information.
- Field Investigation: During public health emergencies, such as bio terrorist attacks and disease epidemics, computerized information systems for data management, analysis and communication may be needed within hours of beginning the investigation. Available sources of data and output requirement of the system may be changed frequently during the course of investigation. Written documents; guidelines and memos important to the epidemics were frequently revised. In this investigation, a database was operational on the second day and the GIS component during the second week of the investigation.
- Tabular Data: This is another type of data commonly used in Geographical Information System (GIS). It involves the use of special data arranged in tables and such data are analyzed and process by computer in order to generate useful information that are relevant to the Geographic Information System.