Geographical information system notes by yusuph
- 1. Functions Of GIS (Data Management And Analysis Procedures) • The functions that a GIS should be able to perform include data input, data management (storage and retrieval) , transformation, analysis and output. a) Data input It is the procedure of encoding data into a computer-readable form and writing the data to the GIS database. • A data input subsystem allows the user to capture, collect, and transform spatial and thematic data into digital form. • The data inputs are usually derived from a combination of hard copy maps, aerial photographs, remotely sensed images, reports, survey documents, etc.
- 2. • The data management functions necessary in any GIS facilitate the storage, organization and retrieval of data using a database management system (DBMS). • The data storage and retrieval subsystem organizes the data, spatial and attribute, in a form which permits it to be quickly retrieved by the user for analysis, and permits rapid and accurate updates to be made to the database. • This component usually involves use of a database management system (DBMS) for maintaining attribute data. Functions Of GIS…
- 3. b) Data transformation and analysis; • GIS excels in data transformation, converting spatial data between entity types (points, lines, areas), and conducting spatial analysis. • In GIS, transformation may involve changing the projection of a map layer or the correction of systematic errors resulting from digitizing. In addition, it may be necessary to convert data held as rasters to vectors or vice versa. • Spatial analysis. This is what distinguishes GIS from other types of information systems. Functions Of GIS…
- 4. • Spatial analysis and manipulation subsystem allows the user to define and execute spatial and attribute procedures to generate derived information. • GIS enables the analysis of spatial patterns and relationships. • It can perform complex spatial analysis, such as overlay analysis, proximity analysis, and terrain modeling, to extract meaningful insights from the data. Functions Of GIS…
- 5. Type of GIS Analysis Procedures Aronoff (1989) classifies GIS analysis procedures into three types: 1. Those are used for storage and retrieval. These tools help store and find things easily. For instance, they can show a map of the soil in a specific area, making it simple to understand and use. 2. Constrained queries. Imagine using a special search that helps you find specific patterns in your data. With this, you could choose to only see or study soils that are prone to erosion. 3. Modeling procedures. It's like using special tools to guess what the land might be like in the future, predicting if certain areas might have soil erosion in strong winds or floods, or figuring out the soil type in an unknown area.
- 6. c) Data output; • Data output is what you get after analyzing information, like maps and tables. • The way it's presented depends on cost, who's seeing it, and the available tools. • It could be simple tables and graphs for a local government or detailed plots for professionals. • Sometimes, it's digital for use in other software, but usually, it's maps.
- 7. Example of GIS output (a) Relief Map (b) Ilala District Map
- 8. Data • We often hear the words "data" and "information," but understanding the difference is key. • Think of data as raw numbers, like those in a table, they're observations from the real world. • Data are collected as facts or evidence that may be processed to give them meaning and turn them into information. • Information, on the other hand, is data processed to make sense.
- 9. • Imagine having field notes on MARUCo, listing data like the campus area, class count, playing grounds, temperature, and student numbers. • These numbers lack meaning until contextualized and properly scaled for interpretation. • To make sense of the data, others need to understand what it represents and the units of measurement used. • It's like having a table of numbers without labels; the context transforms raw data into meaningful information. • With these details the data become information. Information is data with meaning and context added (Hanold, 1972).
- 10. Spatial Data • Spatial data refers to information that has a geographic or locational component. • It includes details about the position, shape, size, and attributes of physical objects or phenomena on the Earth's surface. • Spatial data is characterized by its ability to be mapped and analyzed in relation to its geographic location. • This data can represent various features, such as points (specific locations), lines (connecting points), and polygons (enclosed areas). • It plays a crucial role in Geographic Information Systems (GIS) and is used in diverse fields like urban planning, environmental science, cartography, and more.
- 11. Examples of GIS Data
- 12. Examples of GIS Data
- 14. Sources of GIS Data •GIS has a wide variety of data originating from various sources, however, all GIS data fall into one of the two categories; Primary and Secondary Data.
- 15. Primary Data • Primary GIS data are those collected specifically for use in GIS by direct measurement, • Such direct capturing method include remote sensing that can be imaging or non-imaging data. • There are various range of satellites, optical, IR Thermal and microwave with wide range of spatial resolution for data collection (fraction of a meter to more than 5 km resolution).
- 16. • Closely related to remote sensing data RADAR & LIDAR data capture, the former use radio wave and the later use Laser beam to measure heights • Global Position Systems (GPS) is another method that provide direct data used in GIS, specifically it provides coordinate data. • Data captured in digital format by this method can be directly input in the GIS system or stored elsewhere for later input.
- 17. Secondary Data Secondary GIS data capture are those data collected for other purpose not related to GIS and derived from other sources. Geographical data capture from the secondary source include creating vector and raster from maps, photographs and other hard copy documents. Scanning is one method that that convert analog maps into a digital image Scanned maps and documents are used in GIS as background maps and data storage.
- 18. Manual Digitizing was the most popular method of vector data capture but know is replaced by the more modern methods. Some of the modern methods are Onscreen digitizing, or Heads Up Digitizing and Vectorization. Onscreen digitizing involves digitizing from the computer screen using a mouse or digitizing cursor. A faster method of vectorization is to use software to perform a raster- vectorization.