Lecture - 6 Data Management (AT76.01)

Data Management Dr. Nitin Tripathi RS & GIS FoS ASIAN INSTITUTE OF TECHNOLOGY BANGKOK

Data Management It is the core of the overall GIS It makes information available to the user – User need not be familiar with the database Data Acquisition and Preprocessing – Preparing the data for storage and use Database: A structured collection of information Tools of database management provide safe and efficient access of database to the user

Data Logical Data – The way data appears to the user – Modern database management systems (DBMS) conceals the physical data and presents the logical data to the user – It should be dynamic in nature – It should suit the requirement of the user Physical Data

Principles of Data Management DBMS is a high level computer languages that permits one or more user to work efficiently with the data Essential Components – Delete Old Data – Insert New Data – Modify the Database – The details of data organization in storage is kept hidden from the user – Query of the Information

Defining the Contents of Database Data Format Definition Data Content Definition Value Restriction

Data Format Definition – Integer or Binary – Size – Floating Point Number or Exponential – Predefined String of Characters Data Content Definition – Fields in database should carry useful names Longitude or Road instead of variable 001 or A3 etc. Value Restriction – System must permit constraints on data value These information represent Data Dictionary or Metadata (data about data)

Function of DBMS Security – Mode of access to user and system manager Integrity – Check for consistency – Check for proper datafield – Check for format related constraints

Synchronization – Protection against inconsistency in case of multiple users Physical Data Independence – The basic data storage and manipulation should not matter to the user Minimization of Redundancies – Editing of redundant data becomes complex – In case some data has multiple entry and while editing some are missed, it will cause corruption of datasets

Efficiency Efficiency of data Storage, Retrieval, Deletion and Update depends on many parameters. Two key parameters are ❖Physical Storage Medium Recording Devices: Floppy, Hard Disk, CD ROM Track, Sector, Cylinder Random Access Storage System Cache : A bank of high speed memory Intelligence of disk controller Magnetic Tape Storage: A sequential access ❖Organization of Data

Determination of File Structure It should be determined by : Complexity of the data structure Requirement of data manipulation Type of computer-aided techniques – For example : Regular computer job processing (Termed Batch) or Interactive Manipulation and Analysis

Creation of Spatial Database It is necessary to provide nodes of access for retrieval of both spatial and non-spatial (or attribute) information Search for feature or group of feature – Mode of Query A single feature : Find a second level streams A set of defined features: Find all second and third level steams

– An incompletely defined feature or set of features : Find all features of (type = Hydrography) – Feature based on definite relationship within the dataset : Find all second level streams above 300 m elevation – A set of features in which the criteria are within another dataset : Find second level streams with pollutant levels above state water quality guidelines

Efficient Data Retrieval Operations It depends on Volume of data stored – It affects the data retrieval speed Method of data encoding Design of database structure Complexity of the query

Spatial Database Management Data Management : Efficient use of database (Query, Manipulation and Analysis) Query may range to find out characteristics of a location or locations having specified characteristics

Qualities of a GIS Database Efficiency – Storage, Retrieval, Deletion and Update of large dataset Capability to handle multiple users and database – Support for multiple user and access to database stored at different locations Lack of redundancy of data – Redundancy may cause corruption of data

Data independence – Data and application program should function independently Security – Protection against unauthorized modification Integrity – Ability to protect data from system’s problem through a variety of assurance measures (e.g.., Range Checking, Backup and Recovery) These principles are not firm rules but may be treated as guiding rules. There may be trade off between theoretical preferences against practical considerations.

Strategies to facilitate Manipulation and Retrieval of Large Data Searching Minimize Cost – PAGING (also known as TILING) – RETRIEVAL WITHIN SPECIFIED REGION OF INTEREST – CENTROID AS SEARCH KEY – HIERARCHICAL STORAGE – TOPOLOGICAL ENCODING

ArcGIS Geodatabase



ArcCatalog A catalog window to organize and manage various types of geographic information for ArcGIS for Desktop. • Geodatabases • Raster files • Map documents, globe documents, 3D scene documents, and layer files • Geoprocessing toolboxes, models, and Python scripts • GIS services published using ArcGIS for Server • Standards-based metadata for these GIS information items • And much more

Refer for more information https://nccwsc.usgs.gov/content/data-policies-and- guidance

Data managment is crucial for smooth project