Introduction to_GIS
Contents
What is GIS?[edit]
With the rise of computers, the processing, usage and analysis of spatial data has been playing a key role across all facets of our societies. Within science, diverse fields such as geography, spatial science, data science and many other fields have harnessed the use of information technology to access information sources and to integrate the processing, analysis, and interpretation of spatial data. This development continuously unleashed new potential in how we observe, communicate, and evaluate the spatial patterns, processes and mechanisms that utilize but equally drive the internet and computerization. Within geographical information systems, a generalisation of the world is saved within diverse data formats, ultimately deriving a coarse version that represents the respective spatial phenomena. Geographical information systems -or short GIS- are computer systems for managing, analysing, and displaying data related to positions and geographic information. GIS can show many kinds of data on one map. A GIS facilitates diverse ways to visualize, analyse, and understand spatial patterns and processes. Since much of the data we utilize can be spatially referenced by a coordinate system, GIS data can be facilitated to analyse such spatially referenced information. For example, if we want to know about the number of students participating in different lectures taking place at Leuphana, a simple table cross-referenced with the respective lecture halls might suffice. Yet to enable a spatial representation of the location the students within those lecture halls, a geographical visualization is required (Figure 1).
Definitions[edit]
There are diverse definitions available for geographic information system, e.g.
“GIS is an integrated system of computer hardware, software, and trained personnel linking topographic, demographic, utility, facility, image and other resource data that is geographically referenced. -------NASA
“In the strictest sense, a GIS is a computer system capable of assembling, storing, manipulating, and displaying geographically referenced information, i.e. data identified according to their locations. Practitioners also regard the total GIS as including operating personnel and the data that go into the system.” -------USGS
“A geographic information system (GIS) is a computer-based tool for mapping and analysing things that exist and events that happen on earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps.” -------ESRI
Examples of Applications of GIS[edit]
GIS operate on various levels and typically serve multiple functions. The most basic level to operate GIS is cartography, which is commonly used to map making. GIS can also be used for spatial data analysis.
a. GIS Cartography Maps are an integral part of human development, and many cultures have utilized maps as crucial tools to navigate, explore, describe, and explain. Early maps were essentially an attempt on story telling of distant voyages by cartographers. Cartographers performed the role of artists by creating images based on traveller knowledge, memories, and concerns. With the rise of mathematics, particularly trigonometrics, maps represented spatial relationships that exist in the real world and with the development of technology, maps evolved into digital forms that are now a part of our everyday life due to smartphones, which basically all integrate GIS for localisation and navigation. Geographic Information Systems (GIS), which offer a visual interpretation of data, are mostly focused on mapping. GIS and cartography are being used for an increasing diversity of applications, including integration of Global Positioning System (GPS), remote sensing, global data bases, internet use, web mapping services, and diverse software applications.
b. Spatial Analysis While most GIS applications are related to map making, the term GIS is increasingly being associated with spatial analysis and planning as well. Procedures such as the capturing, visualization, manipulation, and analysis of geographic information are continuously evolving within GIS systems. Environmental management and spatial planning are two crucial fields of application for GIS along with agricultural value chain, public health, and surveying (Masser and Wegener, 1996). GIS has become a standard tool within spatial planning. A broad variety of pre-programmed tools for spatial analysis are available in modern software solutions, such as ARC/GIS and QGIS. Finer scales are approached by architectural tools such as AutoCAD, and programming languages such as Python and R offer an array of tools for spatial analysis. These tools include network analysis, modelling of digital terrain, and spatial overlay. The ability to modify complex and intricate analysis of sequences using continuously evolving programming languages and data bases has become essential in all components of our daily lives. By linking spatial data to advanced analysis approaches the ability of GIS to allow for future predictions and adaptations has become a breakthrough in modern science.
Elements of GIS[edit]
GIS can process both geographic and spatial information at the same time. This requires a variety of functional elements and components. There are five major components including hardware (computer systems, laptops), software (ArcGIS, QGIS, ERDAS etc.), human resources (people with ample knowledge of handling and applying GIS), datasets and analytical methods (Figure 2).
GIS also includes five major functional or procedural elements for successful operation or application. Those are namely: data acquisition, pre-processing, data management and manipulation, and analysis and results generation.
Data acquisition: It is the process of identifying and gathering new data by preparing maps, aerial photography, and surveys. Following table shows few methods of data acquisition:
Preprocessing: It entails changing the data in a variety of ways before entering it into the GIS. Data format conversion and methodically locating objects in the source data are two of the main responsibilities of preprocessing. Extracting data from maps, photos, and printed records (such demographic reports) and then entering it in a computer database are common methods for changing the format of the original data. This process is often time-consuming and expensive exercise. This is especially true when one estimates the costs of moving sizable data volumes from an automated GIS based on computerized databases to paper maps and transparent overlays.
Data Management and Manipulation: The development and accession of the database itself are controlled by data-management operations. Data entry, consistent update, deletion, and retrieval are offered by these functions. The users of contemporary database management systems are shielded from the specifics of data storage. Users typically are not aware of well completed data management processes. Security considerations relate to data management. There must be procedures in place to give various users varying levels of access to the system and its database. Data manipulation consists of working with the database contents to derive new information.
Analysis: Analysis is often the system user's focus of attention. Many people mistakenly think that this module alone makes up a geographic information system. The analytical operators that use the database contents to generate new information are in this part of the system. We need specific facilities to be able to transfer data and information between systems because one system cannot provide the full range of analytical capabilities a user might conceive.
Results Generation: Final outputs from the GIS like statistical reports, maps, and graphics of various kinds are the parts of result generation.
Tutorial on ‘How to download, install and use QGIS’[edit]
Download[edit]
You can download QGIS here: https://qgis.org/de/site/forusers/download.html Select the file that is suitable for your operating system. You can either choose the most recent or the most stable version.
Install[edit]
Open the install-file which you just downloaded.
Note: Your version of QGIS will be a slightly different one since new versions are continuously released. Follow the instructions. You will receive a folder with several QGIS-related files. To start QGIS, open ‘QGIS Desktop’.
Interface overview[edit]
1. Main window: Here, you can view project files and project templates. When you are working on a project, maps are displayed here.
2. In the toolbars at the top, you find basic tools to work with your map (save, undo, redo, cut, zoom etc.)
3. In the toolbox at the right, you find more specific tools that are also intended for certain types of data like vector or raster data.
4. Browser panel: You can access your hard drive to import all sorts of files into your project.
5. Layer Panel: This window provides an overview about all layers that make up your map. You can also change the order of layers here.
6. This is simply a search bar.
7. Status bar: This displays information about your map, e.g. about the scale of your map or the coordinates of your mouse cursor. Also allows you to adjust the map scale, the rotation and the Coordinate Reference System (CRS).
How to open and save a project[edit]
To save a project you are working on, go to ‘Project’ and click ‘Save As…’. This will create a “.qgz-file” which contains all the information of this specific project (layers, project settings, projection for each map view…). This is different from saving a map.
How to save a map[edit]
Project → new print → layout add item → export
Suggestions how to set up your workspace (optional)[edit]
Toolbox Press Crtl + Alt + T to open the toolbox. It will appear at the right site. Via the toolbox, you can access a variety of tools to edit your maps. You can also open the toolbox via the tab ‘Processing’.
Plugins There are two essential plugins we recommend you install right away. Go to the tab ‘Plugins’ at the top and use the search function.
“QuickMapServices” is a repository for basic maps. These are the maps you can use as the first layer of any map you want to create. Imagine you want to create a map of the best ice cream stores in your city. As a basis, you can take a street map for your city from QuickMapServices. After you have installed it, you will find QickMapServices under the tab ‘Web’.
“Spreadsheet Layers” is a plugin to import data from spreadsheet files like excel. One case where this could come in handy is when you collected spatial data on a field trip, documented it in an excel table and want to turn it into a map. After installing Spreadsheet Layers, you can access its function via the tab ‘Layer’ > ’Add Layer’.
The authors of this entry are Neha Chauhan and Christoph Schwenck. Hannah Metke, Carlo Krügermeier and Ben Richter wrote the tutorials.