GGRA30: GIS and Empirical Reasoning

Creating Portable GIS Projects

Technical Memo

Fall 2024

1 Introduction: GIS Project Components

Unlike software with which you may be more familiar, such as Microsoft Word and Excel, typical use of GIS does not store all of your data in one file. Instead, specific geographic data sets, such as informa-tion about roads in your area, are often useful for many purposes and you would not want to have to extract them from an earlier project every time you needed road information for a new map. Because of this flexibility in the use of geographic data, the difficulty involved in maintaining accurate data, and the cost that comes from the effort involved in maintaining and storing geographic information, GIS software tools have been designed to place high value on being able to connect a variety of data sources and formats together. As shown in Figure 1, a typical GIS project can often connect and orga-nize data from a number of sources and can produce data that will be stored in equally diverse output data locations. Once you realize this, an obvious implication is that it is important to develop some understanding of where data is stored and what you are updating when you work on your GIS project. If you do not understand this then you may find yourself wondering “where did my data go?” after you have been working on a project for a while, especially if you find yourself using multiple computers while working on GIS course assignments (e.g., both at home and at campus or using different campus lab computers).

In university GIS courses, you will often be provided with data as a starting point for your assign-ments and you may well find that you use a particular data set only for one assignment (unlike what I

Figure 1: GIS organize a number of information sources and outputs as configured by the settings for a particular project. A flexible approach that requires the user to be organized and keep track of where and how data is stored.

wrote about the frequent usefulness of a regional road layer above, for example). Therefore, to make your studies as simple as possible, I propose a method of organizing your work on each of your GIS assignments, tutorials, and projects to keep all of your project data and configuration information to-gether. This should help you to avoid losing your data and having to start a project or assignment over. With this objective in mind, first, what are the project components shown in Figure 1?

GIS Software The computer application that you use to display, edit, organize, print and manage ge-ographic data about all kinds of things that interest you in the world. For this week’s tutorial and your current assignment, this is QGIS.

Project Configuration The combination of geographic data about a region and how you are using a particular set of software applications to organize, edit, and display that data is commonly called a project. When you carry out such a project, you make a dizzying number of decisions and those must be remembered or else you will have to make them again and again and again. . . These decisions (often referred to as configurations or properties) are stored in a file that details what data your project is using, where that data is stored, and how you want that data to be organized and displayed in your maps or other visual summaries. Typical project configuration decisions could include:

• What region does your map show?

• What data layers are included in your map?

• Where is the data stored for each of your layers and in what format?

• What colour(s) do you want to use to display each data layer (e.g., the roads)?

• How are roads labelled on my map?

• What size page am I planning to print my map on?

• What is my map title?

As you can see, many of these decisions / properties / configurations describe how geographic data is being used within this project. The answers to these questions will change for other map-ping projects without changing the fundamental properties or locations of geographic phenomena such as a particular road’s location or its name.

Geographic data These are data about the location and characteristics of phenomena within the world. For example, the location of a road along with it’s name, address ranges, traffic rules (i.e., is it one-way or two-way), speed limit, etc. These can be any attributes of the particular phenomena being modelled and the exact set of attributes recorded may depend to some extent on the objectives of the people or organization that created the data. Although you may be more concerned about some of the attributes stored for these real world entities than others (i.e., perhaps you care about address ranges but not the direction of traffic flow for these roads), your use of the data in a par-ticular project would not require you to change roads attributes or locations stored in the data unless you were actually changing the roads in the real world.

Geographic data are then information about the world that can be used for multiple purposes and are generally expected to reflect the situation of some phenomena in the world at a particular time, independent of how you might choose to use that data.

Section 2 describes a way to organize a GIS project to keep the configuration and the geographic data together, well organized, and portable. By portable, I mean that your project when organized as suggested can be moved from one computer to another (e.g., from a campus computer to your laptop or home computer) without all of your geographic data “disappearing”.

2 Setting Up a Portable QGIS Project

The procedure outlined below will create a folder for working on your current project and named ap-propriately so that, as a general guideline, a few weeks from now you could look at the folder name and be able to tell what that folder contains. Examples could be GGRA30_Assign1 or GGRA30_Practi-cal6. To reiterate, the purpose of the recommended folder structure is that you will have one folder that contains everything for this work, it will be easy for you to move this folder around with you (e.g., copy to USB key or cloud storage) and continue working without losing data with which you have been working, and later you’ll be able to recognize why you have this folder.

1. Create a new folder. If you are working on a campus computer, creating a folder in Downloads or on the Desktop works well. Name it appropriately, as described above. For the remainder of these instructions, I will refer to this as “GGRA30_SampleProject”.

2. Create a new folder called data inside GGRA30_SamplePro-ject. This will hold any data provided for you and any new geographic data or other files (e.g., exported PDFs of maps) you create while working on your project.

3. Start QGIS. Once the program has started, select Project | Save as. . . (yes, immediately before you do anything else). With the file browser presented, navigate to your GGRA30_- SampleProject folder, assign an appropriate name and save the project file.

The file just created with the “.qgs” or “.qgz” exten-sion is the project config-uration file described in Section 1 and shown in Figure 1.

4. As you create data layers while you are working on your project, ensure that you save them back into the data folder created inside GGRA30_SampleProject. This will keep all of the project data together, while not cluttering the top-level project file so you can easily find and reopen the main QGIS project file when you need to. Generally, you want to access the data files created by a GIS project using the GIS software so the project configuration file is your usual starting point for working with the data as well.

• Note that the first time you save a data file while working on a project, QGIS may default to its installation location as the first suggested folder (and you’ll have to navigate to where you really want to save the file). But once you save a file it should then offer the last folder you used as the starting point for saving other items. Whatever you do and whatever the software does, pay attention to where you save your project and data to make sure you can find it later.

• The folder structure described here is just that: a structure. To ensure that all of your data is kept together, you need to pay attention to how you store data and results and develop the habit of using the storage structure to reduce confusion in your work.

5. You should now have a project folder organized as shown in Figure 2. Work on your project, saving the main project file periodically when you think of it and when things seem to be going well.

6. At the end of your working session, remember to save a copy of the GGRA30_SampleProject folder to a safe storage location (USB key, Dropbox, Google Drive, etc.). As you become more practiced with this procedure, you should use your safe storage location as a backup for your current work and as a known working checkpoint copy.

• Only copy over your backup version of the project if you know that you are replacing it with a new version that represents “progress” toward your completion of the project.

• If you have had some problem while working and the current version you are working on seems to be “broken” somehow, consider not keeping it and reverting to the previously stored version of the project that is hopefully not broken.

• Even though the decision to not save a new backup probably means you will be redoing some work, hopefully from a known good checkpoint, replacing a good backup with a bro-ken update is almost never a good idea.

Figure 2: QGIS project file and folder organization.

Although this memo purports to offer you a useful GIS project organization scheme, it really offers you one of many such possibilities along with advice to develop work practices that will allow you to take advantage of any reasonable organization scheme. The clarification between geographic informa-tion and GIS project configuration is also very useful and you would do well to ensure you understand the difference.