Photo Transit includes some sophisticated elevation planning information to help you virtually scout sight-lines and understand the vertical field of view for your shot.
When the elevation panel is closed, you will see the elevation above sea level for both camera and subject locations. In addition to showing the range (distance) from camera to subject, and bearing (measured in degrees), the app shows the altitude from camera to subject.
Altitude is the apparent angle measured vertically – that is, if you’d need to tilt the camera up to see the subject, then you'll see a positive angle, and if you’d need to tilt down, then you’ll see a negative angle. The altitudes shown in the app are all adjusted for the curvature of the earth. This is an important factor over longer distances (as anyone who has stared at the far horizon will know).
Apparent means that the altitude has been adjusted for the effects of atmospheric refraction. Over longer distances this has the effect of ‘lifting’ objects above the horizon (which is why we see sunrise earlier than we would if there were no atmosphere on Earth).
Correction for curvature of the earth and for atmospheric refraction are two reasons the data from Photo Transit is better than what you would get from simple high school trigonometry (i.e. elevation over distance, assuming a flat, airless Earth).
Vertical Field of View Chart
The vertical field of view chart line, which is displayed on the left hand axis of the chart, shows you two things:
- The apparent altitude along the line from camera to subject, from the photographer’s perspective
- The vertical field of view for the current camera/orientation/pitch/height/lens/focal length combination (shown as two turquoise overlays on the chart – the visible area is between these two overlays)
Both are measured in degrees (°). Double tapping on the chart toggles between zooming in to cover the apparent altitude profile, or zooming to cover both apparent altitude profile and vertical field of view.
Changing any of the factors affecting the camera vertical field of view will adjust the FOVoverlays on the chart.
Elevation Profile Chart
The second data set shown on the chart (optionally – you can toggle one or the other off using the chart legend buttons), is a simple elevation profile showing height above sea level along the line from camera to subject. You can toggle one or the other off using the chart legend buttons.
It is instructive to compare the apparent altitude line with the elevation profile for a hilly or mountainous area you are familiar with. You’ll see that hills close to the camera loom larger in size than more distant peaks. This reflects what the camera will see in real life: if you stand close to the foothills, it’s often impossible to see the mountain peaks behind.
Dashed vs. Solid Lines
The chart lines indicate visibility along the line from camera to subject: areas that cannot be seen by the camera are shown as dashed lines. Areas that are visible are shown as solid lines.
Subject Height Above the Ground
If you specify a subject height above the ground (e.g. the height of a prominent building), then a dashed or solid line is shown at the right hand side of the chart representing the subject above the ground. If the subject is wholly or partially obscured by intervening terrain, then that portion of the subject line is shown as dashed.