From Cardboard Cutouts to Virtual Islands

This tutorial was written by Nick Pigott for the GenesisII and the original is available online from the Ordnance Survey site. However the techniques are applicable to GenesisIV and so is reproduced here. The most difficult stage of the tutorial is generating the landscape from contours, and so we've also included a modified version of the tutorial from Noel Jenkins that takes an in-depth look at these steps. The original for this, concentrating on GenesisII, is available at the Juicy Geography site.

Nick Pigott explains how his Year 7 pupils at Bloxham School, near Banbury in Oxfordshire take traditional landscape modelling into the computer age.

Surely one of the greatest challenges to a geography teacher is to make Ordnance Survey maps come to life. They may be a source of endless hours of fascination to the average geography teacher but to a child they can be dull. Equally, that maze of lines may be as clear as a photograph to the initiated, but to a child...? Particularly esoteric are the wiggling orange lines which are a secret code, accessible only to grown-ups.

So what can be done to unlock one of the world's great mysteries? Here at Bloxham we use a mixture of old and new techniques. We start by building cardboard models, just as I used to in the dark days before the first BBC computer invaded the classroom. This landscape is then transformed through various stages into a virtual landscape, as we shall see.

Preparing the ground

Before undertaking this task, the pupils first learn about scale, symbols and various elementary mapping techniques. They survey sites in the school grounds and prepare plans. Aerial photographs are used to create maps of the school (1:2500 scale) and the village (1:50,000 scale). This work usually ensures the success of the island exercise.

Cardboard island

This task is completed at home and depends heavily on persuading pupils, and no doubt parents as well, to acquire just the right quality of corrugated card. Careful briefing here is essential if bulky, greasy or floppy fiascos are to be avoided. I ask for a base sheet of A4 size and an imaginary island of six layers. We talk about headlands, hills and valleys but experience leads me not to expect too much. I have tried making smaller models of such features in advance, but this tends to negate the purpose of the main exercise. Likewise, dictating the island's contours in advance reduces impact and interest.

Contours, cross-sections and 1:50,000 scale maps

Once I have dutifully admired their creations, I ask the pupils to draw their first map of the island. This comprises just the coastline and contours. Having learned how to draw cross-sections they produce two or three examples for their island and write a brief description of its relief. After discussion about the relationship between contours, physique and landscape they go on to draw a second map to depict the pattern of land use. This is complemented with continued written description and an attempt to draw the island as might be expected when viewed from a boat offshore (having seen a selection of appropriate slides). Finally, the pupils draw a map of their island in strict Ordnance Survey 1:50,000 scale style. A textbook with map symbols and map extracts is available as a source of hints.

Creating a digital terrain model

From this point we leave the world of cardboard and crayons. First the contours of one or two of the best islands are scanned and saved in BMP format. This is then imported into the landscape editor module of Genesis II.

The contour trace tool picks out each contour in turn and allows the operator to determine the height of all points along each line. The software then interpolates the heights for all other points on the map thus creating a digital terrain model DTM.

Additional Notes added by Geomantics: Further details of this process are discussed in the supplementary tutorial.

Rendering virtual landscapes

Genesis now uses the previously generated height data to create what appears to be a three-dimensional model of the landscape. Indeed it goes much further by producing a near-photographic quality rendering of a virtual landscape. First select an environment, perhaps a highland summer evening, and then you select a camera position and target. The software then produces an image, complete with clouds, rocky peaks, sea and waves, which can leave the pupils struggling to believe that there has not been something fishy going on.

Draping overlays over the DTM

Not only can Genesis be used to create a virtual landscape or fly-through; even more exciting is the option to drape an overlay over the terrain model. We scan the pupils' Ordnance Survey maps and again save them in BMP format. The overlay editor module in Genesis then aligns the height data and map symbols and renders the landscape as what is in effect a three-dimensional Ordnance Survey map. It is even possible to explore this unfamiliar world with a simulated fly-through. Now that is bringing Ordnance Survey maps in general, and contours in particular, alive!

Follow-up and further development

Ideally, creation of the 3-D virtual landscape is carried out before the pupils speculate on the land use and Ordnance Survey 1:50,000 scale landscape for the island. If this proves impossible then they can at least critically review their results. The Ordnance Survey map drape also allows the pupils to check their imagined landscape. Are villages in appropriate sites. Do railways take realistic routes? Is the woodland on inaccessible slopes? Further work can explore the issues in planning a new quarry or wind-farm. Our pupils have even written adventures set on the island for the English department.

And where do we go from here? Clearly this exercise is just a start. Real places can be explored just as effectively using digital map data. Local government aided funded schools obtain Land-Form PANORAMA® digital terrain model data of their areas in addition to other digital mapping. The fun has just begun.