In a previous blog on Apps for the Landscape Photographer (click here), I reviewed the CameraAngle app by Geometery (iOS only). This was a clever app to measure the elevation of any subject such as the sun, moon, mountain peak, a building, or whatever. This is an important part of preplanning a shot to determine, for example, when (and if) the sun or moon will be in the right position for a preconceived composition. You can read that blog to see an example where I determined when a full moon aligns alongside the lantern room of a 19th century lighthouse. To accomplish this, I determined the required moon elevation by measuring the height of the lantern room with an inclinometer. There are many inclinometer apps, but CameraAngle was unique because it used the phone’s camera to sight the elevation. Once I had determined the elevation, I used PhotoPills to predict the date and time the moon would be in the desired position. Unfortunately, CameraAngle stopped working when I upgraded to iOS 8 and also is no longer listed in Apple's App Store.
I since discovered Theodolite by Hunter Research and Technology (iOS only at $3.99). There may be a similar (but not the same) android app called Theodolite Droid at Google Play. Theodolite also uses the phone’s camera to sight the elevation, but also incorporates many additional features besides an inclinometer. One important feature is the ability to sight a compass heading through crosshairs. Typically, when determining the azimuth position of either the sun or moon with a conventional compass, you really need a compass with a flip-up sighting mirror (I’ve used my Silva compass for years to do just that). Theodolite, however, allows you to measure a heading by using the camera’s image as a substitute for the sighting mirror. Now, you can position a crosshair within an image and determine the exact elevation and azimuth of that point. You also have the option to read the heading in true or magnetic north.
Below is a screen shot of Theodolite making the same elevation measurement of the lighthouse lantern room that I performed using CameraAngle in my previous blog example. Though there's a lot of screen clutter, you can see the lighthouse lantern room in the center. You have the option to enlarge the image, but it becomes more difficult to hold it steady. The upper crosshairs are positioned next to the lantern room and the elevation angle is shown on the right (red circle) at about 10.4 degrees. Note that this elevation reading differs slightly from my CameraAngle example since I wasn’t standing in the exact same location. Below, circled in blue, is the azimuth angle of 103 degrees (which is true north in this example).
Theodolite does the job, but not without some annoyances – mainly the cluttered screen and small digits. Most times I had trouble reading the azimuth or elevation digital readouts, especially under brighter ambient light. Admittedly, younger eyes may be less bothered by this. The analog scales are easier to read, but I wish they would just reduce screen clutter with simple digital readouts with larger digits. That aside, Theodolite (or its Android cousin) is a handy and inexpensive swiss-knife utility that I would recommend to any landscape photographer.