Use your phone as a tape measure whilst standing still and without having to walk to the distant feature you wish to measure.
Simply hold the phone at eye level and align the cross hair on the ground at the point you want to measure. The phone will display a continuously updated horizontal distance from the camera to the point under the cross hair.
A one off calibration is required where you need to enter you eye level height i.e. the height from the ground up to your eyes.
The distance is calculated by trigonometry so for accurate measurements you need to always keep the phone at your eye level regardless of the angle of the phone pointing at the ground.
If you always maintain the phone at eye level and hold the phone steady whilst taking a measurement you should be able to get a typical accuracy of about +-3cm at 5m distance.
Now supports imperial measurement feet and inches alongside metric meters and centimeters.