Unit 2 Data Processing & Management TYIT SEM VI

Unit 2 Data Processing & Management TYIT SEM VI

Data processing system Refers to hardware and software components which are able to process, store and transfer data OR The components of systems that facilitate the management and processing of geo information.

Hardware and software trends Hand-held computers field surveyors with powerful tools, complete with GPS capabilities for instantaneous georeferencing To support these hardware trends, software providers continue to produce application programs and operating systems significantly more memory Computer networks allowing fast and reliable exchange of (spatial) data Mobile phones with data connection Bluetooth , wireless LAN , copper and fiber optic networks, dial-up

Geographic information systems GIS provides a range of capabilities to handle geo referenced data, including: Data capture and preparation, Data management (storage and maintenance), Data manipulation and analysis, and Data presentation. Earlier : analogue data sources were used, processing was done manually, and paper maps were produced Now : increased use of computers, digital information, software technology geographic information systems

Data requirements Data sources, both spatial and non-spatial, from different national institutes, like national mapping agencies, geological, soil, and forest survey institutes, and national census bureaus. The data sources obtained may be from different time periods, and the spatial data may be in different scales or projections. With the help of a GIS, the spatial data can be stored in digital form in world coordinates. This makes scale transformations unnecessary, and the conversion between map projections can be done easily with the software. With the spatial data thus prepared, spatial analysis functions of the GIS can then be applied to perform the planning tasks.

GIS software The main characteristics : analytical functions that provide means for deriving new geo information from existing spatial and attribute data any package that provides support for only rasters or only objects, is not a complete GIS Well-known, full-fledged GIS packages include ILWIS, Intergraph’s GeoMedia, ESRI’s ArcGIS, and MapInfo from Map- packages Info Corp., QGIS 2.2, 2.8 & 3.14.

Software development in GIS Embedded GIS Professional GIS Desktop GIS Shared Geodata CAD based GIS Open GIS Internet GIS

GIS architecture and functionality Geographic information system in the wider sense consists of software, data, people, and an organization in which it is used. Functional components of GIS:

Spatial Data Infrastructure (SDI) Framework for sharing and integration of spatial data It depends on data, services, policies and application used Framework describes data, metadata, users and tools Standards for capturing, sharing and presentation have been developed by International Organization for Standardisation (ISO) and the Open Geospatial Consortium (OGC) Geo-webservices: software programs that act as an intermediate between geographic data(bases) and the users of the web

Basic software components of SDI Software client: to display, query & analyse spatial data ( web or desktop gis) Catalogue service: discovering, browsing & querying of metadata or spatial data (datasets) Spatial data service: allows delivery of data via internet Processing service: data, projection and scale transformation Spatial data repository: to store data GIS software: to create & update data

Stages of spatial data handling Spatial data capture and preparation Spatial data storage and maintenance Spatial query and analysis Spatial data presentation

Spatial data capture and preparation Data can be collected through : First hand observation primary source Published data secondary source Capturing can be done through scanning, photogrammetric, remote sensing, digitization of analog map, field survey etc From raw base data spatial data sets are derived Data conversion can be requied sometimes.

Data Acquisition Data input methods & devices Manual digitizing coordinate entry via keyboard, digitizing table, stereoplotter Automatic / Semi automatic digitizing Scanner, linefollowing software Existing graphics or Images Real time data GPS, Surveying Existing digital data Topographic maps, road network, Census data

Spatial data storage and maintenance Spatial data is organized in layers Representation of the real world has to be designed to reflect phenomena and their relationships as naturally as possible Vector data types describe an object through its boundary, thus dividing the space into parts that are occupied by the respective objects. The raster approach subdivides space into cells, mostly as a tessellation. These cells are called either cells or pixels in 2D, and voxels in 3D.

Raster storage It is stored in a file as a long list of values, preceded by a small list of extra data (the so-called ‘file header’) that informs how to interpret the long list. The order of the cell values in the list can be—but need not be—left-toright, top-to-bottom The header of the raster file will typically inform how many rows and columns the raster has, which encoding scheme is used, and what sort of values are stored for each cell. Raster files can be quite big data sets. For computational reasons, it is wise to organize the long list of cell values in such a way that spatially nearby cells are also near to each other in the list. This is why other encoding schemes have been devised.

Vector storage Boundary model for polygon

DBMS GIS software packages provide support for both spatial and attribute data GIS applications have been able to link to an external database to store attribute data All major GIS packages provide facilities to link with a DBMS and exchange attribute data with it. Spatial and attribute data are stored in separate structures, although they can now be stored directly in a spatial database.

Data maintenance To keep the data set up-to-date and as supportive as possible to the user community It deals with obtaining new data, and entering them into the system, possibly replacing outdated data. The purpose is to have an up-to-date stored data set available Updation of spatial data is required because many aspects of the real world changes continuously. Local change to the large spatial data set is more typically required. They should leave other spatial data within the same layer intact and correct.

Spatial query and analysis Spatial analysis: GIS operators that use spatial data to derive new geo information. GIS supports spatial decisions. Spatial decision support systems (SDSS): database, GIS software, models and a knowledge engine GIS use the spatial and non-spatial attributes of the data in a spatial database to provide answers to user questions. Analysis of spatial data can be defined as computing new information that provides new insight from the existing, stored spatial data.

Spatial data presentation The presentation of spatial data: in print or on-screen, in maps or in tabular displays, or as raw data The presentation may either be an end-product, for example as a printed atlas, or an intermediate product, as in spatial data made available through the internet