Measure Faraway Objects with SpectaRuler

SpectaRuler (AppStore Link)
User Reviews
Developer: Hollingtech Software LLC
Price: $2.99 Download on the App Store

SpectaRulerSpectaRuler is a very clever utility that allows the user to measure the distance, height, and elevation of objects. How is this possible without actually walking up to the object with a massive tape measure? Through a combination of the iPhone’s camera, accelerometer, touch-screen display, and the addition of a little triangulation (and other difficult math type stuff) SpectaRuler is able to make estimates that are apparently pretty accurate.

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.

Image Gallery: SpectaRuler

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  • Hollingtech Software LLC

    An update will be coming soon that will help clarify this, but I wanted to emphasize the fact that the step count can be set to anywhere between 2 steps and 100 steps. YOU SIMPLY TAP ON THE STEP COUNT (6 STEPS) TO CHANGE IT. A screen shot of this is available on the App Store. Having this range of step counts greatly improves the accuracy on larger objects (like the one in the picture above). Also, concerning the shoe size, because different brands of shoe vary, if you notice the measurements to be slightly too small, try increasing the shoe size by 1/2 or 1 size. If the measurements are too large try decreasing the shoe size by 1/2 or 1 size.

    When used properly, this app produces pretty accurate results (typically ±5%). Please read the instructions in the app. The update (submitted to Apple today) will include the instructional video from our website in the app. The written instructions are also condensed in the update to be a quicker read.

  • Barbara Holbrook

    Great tip on the shoe size! Thanks for clarifying how this app works. I'm definitely going to take it with me on my next excursion to downtown LA. It will be fun to see how the different buildings "measure up."

  • Hollingtech Software LLC

    Hey Barbara,
    Thanks for posting. The instructional video is 8.5 minutes, but I still encourage you to check it out at The best way to dial in your shoe size is to very carefully measure something of known size using the Distance, Height and Width feature (and an appropriate step count). Typically the bigger the object, the more steps you need to take (discussed in the video). Adjust your shoe size and remeasure until you are consistently measuring on target. I have a Master's Degree in Mechanical Engineering and I assure you that the math that went into this app is rock solid (it's the most rock solid of any measuring app I have used). I wear a size 14 running shoe, and to "dial it in", I ended up having to adjust it to 14.5 US Athletic. (Although this is not a guarantee), I measured a wall on the back of my house to within 1.5 inches in each direction. I personally use this app all the time, because it amazes me how well it actually works. I still cannot believe that 2 years ago my wife had to "convince" me to buy an iPhone. Things have changed since.

  • Hollingtech Software LLC

    FYI - Version 1.1 of SpectaRuler is out as of yesterday which incorporates saving, improved instructions, video instructions, and a few other improvements.