Lectures of Geographic Information System

1. Lectures of Geographic Information System Assistant Lecturer Mrs. Hadeel Jamal Ali Academic Year: 2018/2019

2. Definition of GIS: There are many various definitions have been offered that reinforce the major dimensions of GIS. Several of these definitions are listed below. • GIS is a computerized system that is used to capture, store, retrieve, analyze, and display spatial data. • GIS is an information system that is designed to work with data referenced by spatial or geographical coordinates. • GIS use to analyze data about points, lines, and areas to retrieve data for queries and analyses”. • GIS consists of five basic elements: “data, hardware, software, procedure and people”.

3. GIS presents information in the form of maps and feature symbols, and is integrated with databases containing attribute data on the features. Looking at a map gives knowledge of where things are, what they are, and how they are related. A GIS can also provide tabular reports on the map features. Therefore a GIS is a computer-based information system that supports capture, modeling, manipulation, retrieval, analysis, and presentation of spatial data.

4. Components of A Geographic Information System A working Geographic Information System seamlessly integrates five key components: hardware, software, data, people, and methods. • H A R D W A R E Hardware includes the computer on which a GIS operates, the monitor on which results are displayed, and a printer for making hard copies of the results. • S O F T W A R E GIS software provides the functions and tools needed to store, analyze, and display geographic information. • D A T A Possibly the most important component of a GIS is the data. There are three ways to obtain the data to be used in a GIS. Geographic data and related tabular data can be collected in-house or produced by digitizing images from aerial photographs or published maps. Finally, data can be obtained from the federal government at no cost.

5. P E O P L E GIS users range from technical specialists who design and maintain the system to those who use it to help them perform their everyday work. • M E T H O D S A successful GIS operates according to a well-designed plan and business rules, which are the models and operating practices unique to each organization. • HOW A GIS WORKS GIS stores information about the world as a collection of thematic layers that can be linked together by geography location. This simple and powerful for solving many real-world problems from modeling global atmospheric circulation, to predicting rural land use, and monitoring changes in rainforest ecosystems.

6. GIS TASKS General purpose GIS’s perform many tasks. • Input of data • Map making • Manipulation of data • Query and analysis • Visualization of results

7. Input of Data Before geographic data can be used in a GIS, the data must be converted into a suitable digital format. Map Making Maps have a special place in GIS. The process of making maps with GIS is much more flexible than are traditional manual or automated cartography approaches. Manipulation of Data It is likely that data types required for a particular GIS project will need to be transformed or manipulated in some way to make them compatible with system. Query and Analysis GIS technology really comes into its own when used to analyze geographic data to look for patterns and trends, and to undertake "what if" scenarios. Visualization For many types of geographic operations, the end result is best visualized as a map or graph. Map displays can be integrated with reports, three-dimensional views, photographic images, and with multimedia.

8. Coordinate systems: • A coordinate system is a reference system used to represent the locations of geographic data within a common framework. There are two types of coordinate systems used in GIS: • A global or spherical coordinate system such as latitude-longitude. These are often referred to as geographic coordinate systems. A geographic coordinate system (GCS) uses a three-dimensional spherical surface to define locations on the earth. A point is referenced by its longitude and latitude values. Longitude and latitude are angles measured from the earth's center to a point on the earth's surface. The angles often are measured in degrees. Geographic Coordinate Systems that public used is WGS 1984.

9. A projected coordinate system based on various mechanisms to project maps of the earth's spherical surface onto a two-dimensional Cartesian coordinate plane. A projected coordinate system is defined on a flat, two-dimensional surface. Unlike a geographic coordinate system, a projected coordinate system has constant lengths, angles, and areas across the two dimensions. In a projected coordinate system, locations are identified by (x, y) coordinates on a grid, with the origin at the center of the grid.

10. There are many different types of projections, and each one use for the representation of the earth in some way. When selecting a projection for data, it is important to be aware of what distortions are in place. Many common projections are classified according to the projection surface used: conic, cylindrical, or planar. • Conic Projection • Cylindrical Projection • Planar Projection • Transverse Mercator Projection UTM (most use)

11. Data GIS Types The data of GIS have two types: • Spatial • Tabular • Spatial or coordinate data represent features that have a known location on the earth. • Vector: Points, lines, and polygons. • Raster: Row and column matrix. • Tabular • Table or database. • Join with spatial data files by a common attribute (state name, unique ID, etc.). • Map as points using coordinates such as longitude and latitude gathered from a GPS device. • Geocode: associate address fields with a street network.

12. Scale, Resolution and Accuracy in GIS Because GIS data is stored in a very different way than paper map data, the relationships between scale, resolution, and accuracy are very different between GIS and paper maps. What is scale? Scale represents the relationship of the distance on the map/data to the actual distance on the ground. • Map Detail is determined by the source scale of the data: the finer the scale, the more detail. • Source Scale is the scale of the data source (i.e. aerial photo or satellite image) from which data is digitized (into boundaries, roads, landcover, etc. in a GIS). • In a GIS, zooming in on a small scale map does not increase its level of accuracy or detail. • Scale Required: Match the appropriate scale to the level of detail required in the project.

13. Spatial scale Spatial scale involves grain & extent: Grain: the size of pixel & the smallest unit. Extent: the size of study area & the largest unit.

14. Common grain sizes: • 30m : Landsat satellite imagery. • 30m, 10m : USGS digital elevation models (DEMs). • 4m, 1m : IKONOS satellite imagery. • 1m : 2005 National Agricultural Imagery Program (NAIP) photos. • 8ft, 2ft : Quickbird satellite imagery. • 1ft : USGS 2004 color aerial photography. The scale influences two things about a map: • The amount of detail. The map must not be covered with detail, and become too crowded. • The size and placement of text and symbols. These must be sized to be readable at the display scale, and placed so that they do not overlap each other.