– We use all kinds of measuring tools in our everyday lives. Rulers, protractors, squares, and tape measures, et cetera. These work fine for small and medium sized projects, but what if we need to lay out something big, like a road, bridge, dam, or pipeline? Hey, I’m Grady, and this is Practical Engineering. On today’s episode, we’re talking about one of the civil engineer’s most important companions, the land surveyor. And we’re going to do a little bit of surveying you can try at home. (upbeat electronic music) Surveying is essentially the science of taking big measurements.
And you’ve probably seen these guys on the side of the road looking through fancy equipment on a tripod. Just about any civil engineering project starts with a survey to determine the legal boundaries between parcels of property, the location of existing infrastructure, and the slopes and topography of the land. Humans have always had a penchant for building big stuff which means surveying is a career full of history and tradition. Behind every wonder of the ancient world was an ancient geometry nerd who laid out the angles and alignments during construction.
Surveying is also how we created accurate maps of the continents like the great trigonometrical survey of India which took almost 70 years to complete. I personally think everyone should aspire to accomplish something in their life that can be prefixed with the words great trigonometrical. The ubiquitous tool for surveying is called a theodolite, and it’s one job is to measure the angle between two points. Combine those angles with distances from a chain or tape measure and you can triangulate the location of any point using trigonometry.
Modern theodolites called total stations, cannot only measure angles but distance as well, and they have on board computers that can do the calculations and record the data for later use. When you see a surveyor peering through a funny telescope, it’s probably a total station, and he or she is probably sighting a reflector to record the location of a point. (upbeat music) That’s just scratching the surface of sophistication when it comes to modern surveying tools. With GPS and unmanned aircraft, things can get a lot more complicated.
But I’ve got a few ways you can do your own topographic survey at home with fairly basic and inexpensive tools. Maybe you’ve got a drainage issue on your land, maybe you’re planning a landscaping project, or maybe you just want to exercise your God given right to take measurements of stuff, and write those measurements down on a clipboard. That’s my kind of recreational activity. My goal is to perform a leveling survey of my front and backyard, which is just a way to get the relative topography for an area. I laid out a grid of points on a map of my house and then transferred those points to real life using pin flags.
Now I just need to pick my datum, or base point, and measure the relative difference in height between that point and all the others. I tried a few ways to do this and there are no sines, cosines, or tangents required. First a sight level, which is essentially a combination of a telescope and a spirit level. To use it, first get a buddy, or a willing spouse, to hold a surveying rod on the point of interest. Now look through the sight at the surveying rod, and raise or lower the end until the bubble is centered on the line. Once it’s centered, you know you’re looking at a point that is exactly level to your eyes.
If you subtract the height of your eye line with the height measures on the rod, that’s your elevation. It’s not a precision technique, but its is cheap and simple, which is the most you can usually hope for in any part of a home improvement project. The next way I tried, is a water level. Which is literally just a length of clear, vinyl tubing filled with a liquid. As long as there are no bubbles or kinks in the line, the free surface at each end of the tube will self level. I kept one end at my datum, a fixed height, and measured the height of the water at the other end as I carried it around to each of my points.
It’s a little more unwieldy, but it does have a distinct advantage. No line of sight required. You can use this method around corners, or behind trees, with no problem. And again, it’s cheap and simple. The third method I tried worked best for me. My laser level. Here’s the thing, I really like lasers. I relish any chance I get to use them in a constructive way, and this is perfect. The laser level creates a perfectly horizontal line that can be used to line up cabinets, or pictures, or tile, but it also shows up perfectly on a surveying rod.
You don’t need a helper for this method, but you do probably need to wait until dusk unless your laser is really bright, or you have these sweet laser enhancement glasses. This isn’t the cheapest solution for a DIY land survey, but it is the fastest one I’ve tried, and it’s a tool a lot of people already have. (upbeat electronic music) Surveying is one of the oldest careers in the world and one of the most important. Why? Because land is important. If you own some, it’s probably your most valuable asset and even if you don’t, you’re pretty much stuck to it no matter where you go.
As a career, surveying is a fascinating mix of legal knowledge, field work, and technical challenges. And sense civil structures are too big for conventional measurement tools, the surveyor is one of the most important companions of the civil engineer. Thank you for watching. And let me know what you think.