GIS Fundamentals, and Basic Introduction
- 1. BASICS OF GIS IRS -502 Session 2024-25 (4th batch) Institute of Remote Sensing and GIS Jahangirnagar University
- 2. What isGIS? • Is it mapping???
- 3. What isGIS? •What’s the GI? Geographic/Geospatial Information – information about places on the earth’s surface – knowledge about “what is located where”
- 4. What isGIS? • …four main perspectives of the trailing “S”
- 5. Introduction to geographic information systems What is GIS? An organized integration of ➢ Hardware ➢ Software and ➢ Geographic system
- 6. What is GIS? Geographic Information Systems (GIS) is a set of tools that integrate and link various components: hardware, software, human capital, data and processes; that capture, store, manage, analyse and model large amounts of geographically referenced information in order to meet the needs related to planning and management UNGGIM: Americas
- 7. Majority of data and information are associated with some location in space or referenced to the locations on the earth GEOGRAPHIC- Location
- 8. Attributes, or the characteristics (data), can be used to symbolize and provide further insight into a given location INFORMAT ION- Attributes
- 9. A seamless operation linking the information to the geography – which requires hardware, networks, software, data, and operational procedures SYSTEM- Manipulation
- 10. FunctionsofGIS ➢Digitization ➢Editing ➢Topology ➢Projection ➢Format conversion 1) Data Acquisition and Preprocessing 2) Database Management, Update and Retrieval ➢Data retrieval ➢Updation ➢Maintenance ➢Security and, Integration
- 11. Storing Data Personal GDB File GDB Desktop GDB GEODATABASE (GDB) Enterprise GDB Workgroup GDB SINGLE- USER GDB MULTI- USER GDB
- 12. Query • Identifying specific features • Identifying features based on conditions Trinidad Constituencies with an electorate greater than 28,000
- 13. Analysis Which parcels are within 50 feet of the road? Well type Drilled Building owner Smith Soil type Sandy Proximity Overlay Network
- 16. Fundamental Data types 1) Spatial Data Objects or elements that are present in a geographical space or horizon ➢ Map ➢ Image 2) Non-Spatial Data Not involving Space - Describes the quantitative or qualitative characteristic of spatial features For example, area, length & population Spatial data can be mapped and usually stored as coordinate and topology
- 17. Non-Spatial Information Fundamental Data types Source:2023 World Air Quality Report | IQAir Spatial Information
- 18. Spatial Data Spatial Data Models (1) Raster ➢ Defines space as an array of equally sized cells arranged contains in rows and columns. Each cell an attribute value and location coordinates ➢ The spatial resolution is determined by the size of the cell ➢ Data values for a given parameter are stored in each cell – these values may represent an elevation in meters above sea level, a land use class, a plant biomass in grams per square meter, and so forth Structure of raster data model showing the matrix structure into row and column of the cells
- 19. The spatial resolution is determined by the size of the cell Spatial Data SENTINEL, 10 M GOOGLE EARTH
- 20. Two forms of raster data 1) Continuous Raster ➢Numeric values ranges smoothly from one location to another 2) Discrete Raster ➢Relative few possible values to repeat themselves in adjacent cells Spatial Data Pm 2.5 Pm 2.5
- 21. Spatial Data Models (2) Vector ➢ Objects are represented as Points, Lines or Polygon ➢ The position of each object is defined by a (series of) coordinate pairs ➢ A point is described by a single X-Y coordinate pair and by its name or label e.g. buildings, trees etc. ➢ A line is described by a set of coordinate pairs and by its name and label e.g. streams, streets, sewers An area, also called a Polygon, is described by a set of a coordinate pairs and by its name and label, with the difference that the coordinate pairs at the beginning and the end are same .e.g. Land parcels, cities, countries, forest, rock type etc.
- 22. Topological property of vector data model Set of rules that model the relationships between neighboring points, lines, and polygons and determines how they share geometry Connectivity: Information about linkages among spatial objects. Arc node topology supported through an arc-node list. For each arc in the list there is a from node and a to node. Connected arcs are determined by common node numbers Contiguity: Polygons share a common arc. Contiguity allows the vector data model to determine adjacency Containment: Geographic features cover distinguishable area on the surface of the earth. An area is represented by one or more boundaries defining a polygon
- 23. Conversion of vector to rater Conversion of raster to vector Input raster Simplified Non-Simplified
- 24. Spatial Data Raster Vector Data structure Advantage Simple Complex Disadvantage Overlaying Easy and efficient Difficult to perform Compatible with RS imagery Yes No Efficient representation In-efficient representation High spatial variability Yes Complex Programming by user Compact data structure Disadvantage No Yes Advantage Efficient encoding of topology No Yes Easy editing No Yes Network analysis In-efficient Efficient Map output Less accurate Accurate Projection transformation In-efficient Efficient
- 25. Spatial Data Raster Vector Digital remote sensing images Primary GPS measurements Digital aerial photographs Survey measurements Scanned Maps Secondary Topographic survey Digital Elevation Model (DEM) images Toponymy data
- 26. Non-Spatial Data Attribute Data ➢ Commonly arranged in tables where a row is equivalent to one entity and a column is equivalent to one attribute, or descriptor, of that entity ➢ Typically, each row relates to a single object and a geospatial data model ➢ Usually, each object will have multiple attributes that describe the object
- 27. Related to names Sequence or ranking Non-Spatial Data Attribute Data Type Both values are equally important Both values are not equally important •Date: This data type stores dates and times in the format as hh:mm:ss’ ‘mm/dd/yyyy
- 28. Questions Answers FALSE ➢ The no. of population at each district of Bangladesh represents nominal data- TRUE ➢ The data collected via GPS on field is of which type of data source? PRIMARY ➢ Excel sheet representing Rows and Columns for different agriculture data represents? NON-SPATIAL ➢ Vector data are well-suited for representing continuous phenomena like elevation or temperature FALSE ➢Thenames of different crop typesof Bangladesh representnominal data-