A scholarly resource must be written by a scholar - an expert in the field, usually with a PhD or equivalent qualifications. Scholarly resources usually tell you about the author, so that you can assess whether s/he is a reliable expert on the information presented.
Walkmeter uses GPS to measure the distance of your walks and hikes outdoors. It functions much like a stopwatch. Open the app, tap Start, and use Lap when you want to log an interval. It maps your walk, and you can view time, speed, distance, and pace as you walk.
You can not only measure an object but also the distance between two walls. *** Only on iOS ***. To try this technology for free you can install the app Move to measure - Goniometer. This free app measures the angle as you move the device.