We use all kinds of smaller measuring tools in our everyday lives such as rulers, protractors, and tape measures. These tools work fine for home projects, but what if we need to layout something large like a road, bridge, dam, or pipeline?
Surveying is the science of taking big measurements. You’ve probably seen these guys on the side of the road looking through fancy equipment on a tripod. Almost any civil engineering project starts with a survey. This is to determine the legal boundaries between parcels of property. Surveying is also used to determine the location of existing infrastructure, and the topography and slopes of the land. Humans have always had a penchant for building big stuff. This 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. This took almost 70 years to complete. Everyone should aspire to accomplish something in your life that can be prefixed with the words “great trigonometrical.”
The ubiquitous tool for a survey is called a theodolite, and it’s one job is to measure the horizontal and vertical angles between 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 onboard computers to 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. For long distances, these measurements have to be corrected for variations in earth’s gravity, refraction by the atmosphere, and yep, even the curvature of the earth. But don’t tell the flat-earthers. We’re sworn to secrecy along with NASA employees and airline pilots.
That’s just scratching the surface of sophistication with modern surveying equipment. With GPS and unmanned aircraft, surveying can get a lot more complicated. But I’ve got a few ways you can do your own topographic survey with fairly basic and inexpensive tools. Maybe you’ve got a drainage issue on your land or 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 a surveying rod and raise or lower the end until the bubble is centered on the line. Once it’s centered you know that you’re looking at a point that is exactly level to your eyes. Simply subtract the height of your eye-line with the height measured on the rod and that’s your elevation. It’s not a precision technique, but it is cheap and simple which 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 measure the height of the water at the other end as I carry 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 a cheap and simple solution.
The third method to take a level survey 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 perfect horizontal line that can be used to line up cabinets or tile, but it is also super easy to read on a surveying rod. You don’t need a helper, 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 tried, and it’s a tool a lot of people already have.
Surveying is one of the oldest careers in the world, and also 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, fieldwork, and technical challenges. And since most civil structures are too big for conventional measurement tools, the surveyor is one of the most important companions for the civil engineer. Thank you for watching, and let me know what you think!