What does the Acronym GIS abbreviate?
GIS = Geographic Information System
Features such as the ones illustrated above are located in space in some sort of a coordinate system and have qualities that set them apart from each other. Lines can lead to complex lines –> to closed lines (polygons) and changes in direction or type can be marked with points. Think of Features as objects you will find on the land – such as lakes, rivers, roads, buildings and points of interest. We use GIS software and other spatial software to create and store these features digitally.
For Geog 204, we will generally be using a file type that can contain one feature type at a time (either Point, Line of a Polygon). We will discuss this later in this lecture.
Data that describes geographical features. Data used in the field of GIS tend to be tabular (but it is not always the case) and have the same structure as data stored in a spreadsheet. In GIS many data tables can be utilized to connect attributes to features.
The system in GIS is a combination of hardware, software and users. Classically GIS work had been done through a central computer environment or specifically designed workstations. This classic approach made use of proprietary software and highly trained people with a deep knowledge of GIS techniques.
Historically GIS has been considered a tool
A GIS provides results from data input and analysis based upon a query put forth.
Common steps in this manners are:
- A GIS specialist is given a problem to solve based on qualities described by other professionals
- This specialist assembles the necessary data to complete the task
- these data modelled and analyzed
- descriptive products that attempt to provide solutions for the problem are provided(such as maps, tabular information or statistics).
Data used in a GIS are usually made up of layers that can be queried in a variety of ways
- we will see these methods in future lectures, labs and tutorials.
Below is a figure from http://geography.name that represent possible spatial layers that can be combined to provide insight to research questions (results).
Some Key points and Terminology we have come across so far in the course:
We have used computers a fair bit in this class considering this is the first content lecture we have had. From the use of computers for GIS there have been concepts that we should take some time to reintroduce and review. It is fundamental to remember that you are intelligent capable people that will gain a real understanding of GIS and associated principles. There is a certain amount of confidence you will gain from this course that will help you in other courses and possible employment in regards to information gathering and computer knowledge.
GIS – Definition
Geographical (geography in the spatial meaning) – place in space (G)
Information describing the geographical locations – called attributes that are generally stored as tables (I)
System – combining people’s technical and intellectual knowledge by using computer hardware and software (S)
Files – Where data is stored and good practices in storing the rapidly growing GIS datasets we will be working with. What kind of files (formats) the data may be in.
Features – What we see on the landscape and how we choose to create them digitally.
Feature Types – We focus on three types of features–> Point Line Polygon We tend to store our features as one feature type per file.
Layers – Geometries and associated attributes are stored, presented and analyzed as layers (files hold data that is opened as a layer in GIS software). For the most part there is one layer per file.
Classic GIS – Historically thought of as a tool with specialized training and software necessary to mange data and produce analytical results.
Some examples and explanations of these terms:
Acquiring and storing data: Files
In the lab we will be storing our data in files (not in a central database). We need to organize our data in a well defined tree structure for storing and altering these files and remember what the types represent. Because we use a common place (for Linux and Windows) to store everything, we will be able to access and manipulate our data easily. It is still important to understand where our data is and to be able to move, add to it or remove these data.
If /home is the starting point or our storage tree, what are the branch names leaf names of the following location for spatial data: /home/labs/geog204/tutlab1/pgbears.shp?
What format of spatial data is pgbears.shp (HINT: QGIS uses these data types primarily)?
What other files would you expect to fine in the same directory?
If you wanted a copy of pgbears.shp, how would you go about getting it to your own directory?
If we consider a shapefile to hold geographical and attribute information, then it must contain a spatial layer. A spatial layer, or GIS layer is intrinsic in its name. You can have a layer of grime on your car that you traced out “wash me” in and in several days that layer has been covered with more grime. The “wash me” notation may appear faint after a period of time, but if you could strip off each layer until you reached the “wash me” it would appear clear again. This is the same with GIS layer (as illustrated in the first section). You add as many layers to your work area as you need for presentation or analysis.
As we have found out, shapefiles for instance can only carry one layer in each file, so file names and layer names become synonymous. The type of analysis and mapping that can be carried out is dependent on the type of each layer.
Features and Feature Types:
Layers contain features within them. Many would consider that Quesnel Lake would be a feature to be stored in a GIS. It indeed can be stored in GIS but it is stored as a polygon. It is a polygon feature type that would be stored in a layer that contains only polygons (in a shape file), but not all of those polygons would have to be lakes. Each individual feature (each polygon) is unique in the shape file and its table attributes may be used to determine if it is a lake or not.
Movement to newer GIS strategies
In this course we will take these foundations of GIS and investigate approaches that are moving GIS into a method of integrating many fields of interests from a set of tools primarily used for land use concerns. Contemporary GIS uses many of the same techniques practiced in Computer Science for acquiring, storing, manipulating and sharing data. Some of the newer fields and standards that have evolved are:
We will be discussing newer methods of standardising as well as expanding the use of spatial data for an increasing human need for spatial information.
As GIS is becoming more widely used in all types areas the methods by which it is used is constantly being updated and improved upon. This has resulted in people other than GIS professionals needing to understand and apply some of these newer techniques. This expansion of GIS has lead viewing GIS as a science rather than strictly a technology or tool, and has spawned newer acronyms such as GISciences and GITechnologies.
In this class we may use our software and hardware as tools, but we will be applying strategies used in science (social science).