QGIS & OSM: Highlighting Historical Roads

by Andrew McMorgan 42 views

Hey Plastik Magazine readers! Let's dive into something super cool today: using QGIS to highlight specific roads on OpenStreetMap (OSM) data. Specifically, we're going to tackle a common challenge – visually emphasizing historical routes, like the iconic Great Northern Road in the UK. This is perfect for your GIS projects, especially if you're working on something historical or geographical! So, if you're looking to showcase a specific road network in QGIS, you're in the right place. We'll go through the steps, troubleshoot some common hurdles, and get you highlighting those roads like a pro. Whether you're a student working on a project or just a GIS enthusiast, this guide will provide you with the tools and knowledge to achieve your desired results. Let's get started, shall we?

Understanding the Challenge: Highlighting Roads in QGIS

Alright, guys, let's get down to brass tacks. The main goal here is to make a specific road – in this case, the Great Northern Road – visually stand out on an OSM map within QGIS. It sounds simple, right? Well, it can be, but it often involves a few steps to get the desired result. The main challenge often comes down to accessing and manipulating the road data effectively. You'll likely need to either extract the specific road data or filter the existing data to show only the road you're interested in, and then style it accordingly. You might be tempted to just download a shapefile of UK roads and call it a day, but that can sometimes be a bit clunky, especially if the shapefile isn't perfectly up-to-date or doesn't have the specific attributes you need. That's why we're focusing on OSM data, because it's usually current, open-source, and allows for more flexibility.

So, what are we actually trying to achieve? We want to see the Great Northern Road clearly displayed against the backdrop of the rest of the UK road network. This involves choosing a good color and line style for the highlighted road. Think about things like the thickness of the line, the color (maybe a historical color, if you're feeling fancy!), and whether you want to add any other visual cues like a dashed line or a glow effect. We'll also need to consider how to handle overlapping roads, because the Great Northern Road is probably going to cross other roads, so we want it to be clearly visible. It's all about making the road stand out in a way that's both informative and visually appealing. Remember, clarity is key here. The point is to make the route easily discernible without making the map cluttered or confusing. We want to tell a story with our map, and the highlight is the main character!

This process is not just about aesthetics; it's also about accuracy and historical context. Highlighting a historical route like the Great Northern Road requires understanding the evolution of road networks. You'll need to know which sections of modern roads correspond to the historical route, which might require cross-referencing with historical maps or other sources. This is where the power of GIS really shines, allowing you to blend the past with the present, and to convey a deeper understanding of the geographic context. Now that you've got the basics down, let's start actually working with QGIS.

Step-by-Step Guide: Highlighting Your Road

Alright, let's get our hands dirty and start with the QGIS magic. I'll provide a simplified guide, assuming you have QGIS installed. Don't worry, this isn't rocket science, and we'll break it down into easy-to-follow steps:

  1. Get Your OSM Data: First things first, we need to get the OSM data for the UK. There are a couple of ways to do this. The easiest method is to use the QuickOSM plugin in QGIS. Go to Plugins > Manage and Install Plugins and search for QuickOSM. Install it. Once installed, go to Vector > QuickOSM > QuickOSM. In the "Key" field, type "highway". In the "Value" field, you can leave it blank to get all roads, or you can specify a more particular type (like "primary", "trunk", or whatever is relevant to your route). In the "In" field, select "Canvas Extent" if you want to focus on your current map view, or "Country" and select the United Kingdom. Click "Run". Now, you should have a road network loaded onto your QGIS map. Another option is to use the 'Download' option from the OpenStreetMap website, and import the downloaded .osm file into QGIS (you might need to install the 'OSM place' plugin to import this). This allows you to select exactly the area you want. This option is great for large area selections.

  2. Identify Your Road: Next, we need to pinpoint the Great Northern Road. This is where a bit of research comes in handy. You might need to use historical maps or online resources to identify the precise route. This could involve cross-referencing the road names, especially in the OSM data with the historical route you are trying to find. This might require creating a temporary layer in QGIS to show the general path to guide yourself. This is great for more complex routes.

  3. Filtering the Data (The Crucial Step!): This is where we tell QGIS to only show our specific road. This uses the attribute table of your road network layer. Right-click on your road network layer in the 'Layers' panel and select 'Open Attribute Table'. Each road segment in your dataset should have attributes like road name, type, and more. Look for an attribute related to the road name (e.g., "name", "ref", or similar). If you already know your road name, you can filter directly. Click the "filter" button at the bottom of the table and use an expression like `