Aerial photography and procedure in surveying

5 Questions About Aerial Photography and How It Sculpts Today's Maps

UAVs, also known as drones, have become ubiquitous over the last few years. Industries ranging from entertainment to energy production have all found useful work for drones to do. The advent of cheap trips to the sky has allowed for accurate aerial photography. What use do UAVs and satellites have for the surveying and land development industry?

What is the difference between aerial photography surveying and aerial photography in general?

Aerial photography refers to images taken from any craft in the air aimed down at the ground. An aerial photography survey is more nuanced since it requires accurate measurements and scale. With so many angles, lenses, and exposure decisions to make, a simple ground photograph taken from the air doesn't give us much worth using in the world of land surveying.

Aerial photography and procedure in surveying

Aerial photography is often separated into two groups: vertical shots and angled shots. Both of these perspectives have their benefits and drawbacks. For scientific purposes, the angled perspectives are good for capturing mountains and other geographical features, which is something a vertical-only perspective can not achieve.

Aerial photography, in general, might have some usefulness for archaeology and certain cartography, but it isn't very useful for surveying. Photography that can be adapted to show accurate scale is still needed.

What is Aerial Photogrammetry and Why Is It Useful for Land Surveys?

As defined, photogrammetry is the use of photography in surveying and mapping to measure distances between objects. When this practice is done from up in the sky, it's known as aerial photogrammetry. An aerial survey can certainly be useful if we can design a way to measure distances accurately between two points on the ground from up in the clouds.

This form of aerial photography survey requires taking a staggering amount of photographs and stitching them together to form a sort of map. With more images comes a higher resolution map, which in turn gives us higher accuracy surveys.

While the concept of modern photogrammetry was devised over 150 years ago, accessibility has limited surveyors. Now with technology opening doors we never thought possible, taking thousands of pictures from up in the sky has become safer and cheaper than ever before.

What is Metric Photogrammetry?

Metric photogrammetry is used to determine dimensional measurements of features, distances, volumes, elevations, cross sections, and to help create maps. Points and coordinates are used to measure accurate distances and apply the measurement throughout the photo array.

What is Interpretive Photogrammetry?

Interpretive photogrammetry deals with textures, shapes, and colors found in images. The field of remote sensing is based primarily on interpretive photogrammetry applied to different photographic arrays. The concept is expanded across the spectrum of radiated light. By using infrared and x-ray telescopes, scientists can peer into worlds that are invisible to the naked eye.

How Are We Able To Form Accurate Measurements?

The idea behind forming measurements and scales from images is intuitive for humans. After all, the images represent what we see, and we naturally want to size up the things we see.

Aerial photography and procedure in surveying

The key is triangulation. Simply take two photographs of the same object from two different locations and now you'll have two lines of sight, or essentially two sides of a triangle. With a little math you can figure out the third line of sight in the triangle, and voila, measurements can be made. It's a bit more complicated than this, but that's the gist of it.

Satellites have allowed GPS systems to use triangulation, in the same way, to help people all over the globe to estimate distances based on two known points. We take for granted that our cell phones can triangulate where we are based on the triangulation from GPS satellites in addition to the measured triangulation from the cell tower we are currently connected to.

At the time we were estimating the distance from the earth to the sun, we didn't have the technology to launch satellites or fly drones overhead to grab aerial photography survey measurements. Now we have not only the technology, but we have a relatively inexpensive way to fly drones and launch satellites that we simply didn't have before.

We should take a moment to recognize how great aerial photography is. Not just for its ability to show us incredible images from the viewpoint of a bird, but for its ability to help create maps and survey land for the development of civilization. So, the next time you ask your phone for directions to the nearest Walmart, have a quick look at the sky above and see if you can spot the satellite making it possible.