Rulers and forensic scales require the same process for track size. Due to the diversity of items being photographed, forensic size reference scales are used to accurately scale items.

Yardsticks and tape measures are slightly better than standard-size reference materials, rulers or forensic scales in that you can obtain a rough measurement directly from the photograph. The main problem with this approach is the difficulty in being able to read the measurement in the photo. A secondary problem is properly lining up the end of the track with the end of the tape measure or yardstick. Measurements can be off by one-half inch or more if one is careless in this regard. In addition, yardsticks are awkward to carry in the woods for any distance.

A track caliper is a better choice for researchers in the field. You can make these out of any number of materials, like wood, plastic or metal. Five areas crucial to creating a reliable tool are:

1. Accurate placement of measure lines. Take excessive care in getting the spacing correct.
2. 90-degree angle at the stationary bar.
3. 90-degree angle at the adjustable bar.
4. Cut away for clear reading of measurement.
5. Large clear printing of the measurement numbers.