Remember that high school math class that most students despised, trigonometry? It’s back, and it’s on steroids. Gigabyte steroids. Drones and laser scanners both collect data that is processed with trigonometry, but the data and the methods used in each technology are quite different. This edition of our newsletter focuses on the differences between the two so you can pick the most efficacious solution for your situation.
Let’s start with collecting data. Laser scanners shoot laser beams. Lots of them. When a beam bounces off an object and returns, the scanner captures a full 3-dimensional measurement (X, Y, Z) of that point. Drones typically carry high-resolution cameras and capture a series of digital photographs of the object or scene from different angles. Both instruments are limited by distance. The laser scanner must be close enough for the rebounding beam to return to the sensors in the scanner. For drones, the farther they are from the target area the lower the resolution, meaning each pixel represents a larger surface area.
Laser scanners perform well both indoors and out, even in small spaces. Drones are limited to out of doors, unless your “indoors” is a great big empty.
Both technologies generate enormous data files. Laser scanners take 1 million measurements per second. Each photo or video frame captured by a drone is typically 12 Megapixels. Expect Gigabytes of data from either.
For either scanners or drones, the data must be processed to be useful. Enter trigonometry. Photogrammetry is the trigonometric method used on drone data. As long as the digital photos contain at least one object of known dimensions (this is critical) the software can calculate the dimensions of any other feature in the images by comparing the angles and apparent distances in the images. (This technique was actually invented in the 19th. century, but before computers and digital cameras were invented, it was impossibly tedious and time consuming.) Also, drones can be equipped with cameras to record light frequencies that are not visible to the human eye. This allows analysis that is not possible with laser scanning data.
For laser-scanning processing, the measurements and other data taken from all the scanning positions must be aligned to the same coordinate system and purged of a few anomalies.
So how do you choose a particular technology for your situation? Start with this chart.
Still not sure or have more questions? Give us a call or drop a line.