The way to use the app is very particular– and a little surprising– so it’s very important to configure SpectaRuler properly and read through all the instructions before you begin. In a nutshell, this means configuring the accelerometer and telling the app what size shoe you wear. That’s right: your shoes are of the utmost importance.
Here’s why: SpectaRuler works by recording the relative size and angle of objects that are captured with the camera. Then, the user has to carefully walk either three or six steps, placing one foot in front of the other, so that the app can then record the difference as it appears through the camera. By analyzing the difference between these two images, and by knowing the precise distance between where the two were recorded, SpectaRuler can figure out all the relevant measurements.
So, how accurate is SpectaRuler, anyway? That depends, first of all, on how meticulously the app was calibrated, how steady the user’s hands are, and just how much the user’s shoes conform to the standard. The math behind the program is sound, so in ideal conditions one can expect the end result to be somewhere between “pretty close” and “that seems about right.” Unfortunately, if you’re in the position to estimate the height of an object with your iPhone, chances are there’s no way to confirm how close SpectaRuler’s final estimate is.
The good new is, it doesn’t need to be exact. This is an app that is intended to entertain, to satisfy one’s curiosity, and to add to the ever-growing list of all the cool things a smartphone to do. If you want to use this app for professional land surveying purposes, well… don’t. If you just want to make your buddy raise an eyebrow, or figure out roughly how far you’d plummet if you were to step out your apartment window, SpectaRuler is easily worth the price.