By Aranya
Introduction
If you are lucky, you will have obtained a good map from your client, on which you can base your own. Maps are made for many different reasons though, and it is unlikely that even if you have, you will be holding the perfect map for you in your hand just yet. However, even a basic outline of a site is good starting point that will save you a certain amount of surveying work. I’ll assume though that you were not so fortunate, and that you have had to create a base map from scratch. Hopefully you will have sketched out a simple map, something like the one shown here, while doing your survey. This example however, shows only basic measurements and angles; I recorded additional information onto overlays for clarity. So first of all we need to determine the scale of our map. This we decide by identifying the longest dimension of the site and the size of the paper we are intending to use for our drawing. In this example, the approximate site dimensions were 25 metres by 12 metres. As the longest dimension was significantly longer than the shorter one, I used this to guide my choice of scale. I decided to draw the base map onto A3 paper (420mm x 297mm). Normally I might have divided the longest measurement (25 metres) into the longest side of the paper (420mm), but I noticed than I could still fit the longest dimension onto the page diagonally, if I chose a scale of 1:50 (25 metres into 500mm). Interestingly, this also allowed my north arrow to point to the top of the page.
Drawing your base map
So having decided upon your scale, calculate the distances each boundary will reduce down to on your drawing (a scale ruler can make this job much easier). Divide the real life distances by the scale ratio (in this case 50), to calculate the measurements on your drawing. Then, marking lightly at first with a pencil, until you are sure your markings are correct, start adding details to your map as follows:
1. Draw in the main site boundary points Determine the best side of the site (usually the longest) to act as a base line and mark this on your drawing. To do this, you need to have an approximate sense of where all of the main outside points (boundary corners, gateways, adjoining buildings etc.) are going to be. Having marked out your base line, you can now use your site measurements (and angles if you used a compass) to plot out the other points around the site boundary on to your drawing. This can be achieved either by obtaining on-site measurements across diagonals, or by using a compass and triangulation. A pair of compasses is certainly useful at this point for drawing arcs, but you could create the same effect using a long piece of paper with a couple of tiny holes at either end.
2. Join your boundary points together If the distances and angles look correct, then join the points together to create your boundary. It should at this point look correctly proportioned – if not, recheck your measurements, it can be easy to miscalculate measurements when scaling down distances.
3. Plot the main features in the middle of the site Using the same technique with a pair of compasses or the long piece of paper, plot the key elements in the middle of the site. These could be trees or whole buildings depending upon the size of the site / scale of the map. In this example, the mobile home was in the middle of the site, so I originally took bearings and paced distances from different corners to points around the boundary. This allowed me to position the structure accurately on my map (here is the final base map before overlays, as you can see it is quite simple);
4. Add the first overlay and plot the less permanent features All the detail you have plotted on your map up to now is likely to still be present in your final design. Anything that you are not sure about keeping should be drawn onto a separate overlay. That way you will have an accurate record of the placement of elements on the site, without being influenced when it comes to your final design about whether they should remain – either in their present position, or at all. These elements might include plants, movable structures (e.g. sheds), paths etc. You may come up with much better design placements.
5. Add the second overlay and colour in the zones Now we are going to add some detail that will help us in our analysis, but we won’t want it cluttering up our final design drawing. Place your overlay, marking boundary corners as usual for accurate alignment, and colour in the different zones that you have identified.
6. Add the third overlay and draw in the different sectors Our third overlay is for mapping out the sectors that we have identified. Again, while this is all useful to us in making choices, most of this information will be surplus to requirements on our final design drawing. This is why we once again use an overlay, rather than plotting it on the base map.
7. Add any further overlays and fill in additional details It may be necessary to add further overlays to record any additional information that may help you in making decisions; such as the routing of utilities underground. You should now have an accurate base map with a series of overlays that you can use in your analysis. But before that, onto the next stage - the client interview (part 3).
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