GI explained


Exploring our surveying antiques

The prospect of the upcoming move to our new head office has resulted in buzz of increased activity around the building in recent months. Just like when you move house, it’s been a good time to have a bit of a clear out and take stock of what’s been hiding under the proverbial bed or in the attic.

Well, part of that process has included cataloguing the many pieces of antique surveying equipment that have been accrued by Ordnance Survey over the past 200 years. Some of the items have played an historic role in the birth of modern map making in Britain and are irreplaceable.

To understand more about some of this fascinating equipment, I caught up with Ken Lacey, a surveyor by trade who now works in our education team. Ken was kind enough to give me a tour of what is rapidly turning into an Aladdin’s cave of cartographic memorabilia, with two pieces being of particular interest. Read More


Time to rethink the design process: colour blindness and maps

There is a genetic disorder that affects up to 10% of men and about 0.5% of women. It impacts on their daily lives, often making the simple everyday tasks difficult and crushes the dreams of budding pilots and wannabe coast guards everywhere. Yes, it’s colour blindness. But for something that is experienced by a sizable minority of the population, colour blindness seems to play a relatively small role in the design process. Think weather forecasts, snooker and, yes, maps. The traditional rainbow of cartographic colours – greens for vegetation, reds for main roads and footpaths, and blue for motorways and rivers – can become indistinguishable, therefore making map reading really difficult Read More


What’s the difference between raster and vector mapping?

People ‘in the know’ when it comes to geography often talk about ‘raster’ and ‘vector’ mapping, but sometimes they forget that to ordinary people, these terms are pretty mysterious. So, I thought it would be useful, as part of our posts around GI explained, to try and describe the difference.

Raster mapping

OK, this is the easier of the two to explain. A raster map is basically a ‘dumb’ electronic map image made up of a set number of pixels. You can’t manipulate the information, move a place name around for example, and when you zoom into the map, it quickly becomes pixellated and unreadable, just like a photo taken on a digital camera. This extract from an OS Landranger Map is an example of raster mapping – full of detail and great if all you want to do is navigate or perhaps overlay some other information, like a walking route or flood plain.

This extract from a OS Landranger Map is an example of raster mapping

This extract from a OS Landranger Map is an example of raster mapping

Vector mapping

Right, now things get a little more complicated so bear with me. A vector map, like OS MasterMap, is basically a database of points, lines and polygons which collectively make up all the features on the map. It’s possible to assign each of these features extra information – perhaps demographic data and the age of the buildings for example. Using a Geographic Information System, or GIS, it’s then possible to do all kinds of analysis. For instance, you could ask the GIS to highlight only the buildings older than 50 years, with inhabitants aged between 30 and 40 living within 10 miles of a certain point. It’s the ability to do this kind of analysis that makes vector mapping such a powerful decision making tool.

I hope that makes sense. If you’ve got any questions, or can think of better explanations, please let me know!

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