The Ruler tool can be used to measure small objects or distances on a map.
Place the object next to the ruler and tap the screen to mark the end of the object. The exact measurement will be displayed at the top of the screen.
By default, the ruler will respect the distance units in Settings > Units. You can change the units of the ruler between centimeters and inches by tapping the units at the top of the screen.
To measure distances on a map, you need to know the map scale. If it says something like 'Scale 1:62500', then you can use the 'Ratio' scale on the Ruler. If it says something like '1 inch = 1 mile' or has bars that can be measured, then you can use the 'Verbal' scale.
Once the scale has been entered, measure the distance on the map, and the map distance will be displayed at the top of the screen.
Most devices correctly report the screen size, but you should compare Trail Sense to a physical ruler to make sure it is accurate.
If it is not accurate:
For example, if Trail Sense reported 1.5 cm when you measured 1 cm on the ruler, enter 1.5 as the ruler scale.
You can enable the Ruler quick action in the settings for the desired tab.
To use the quick action, tap the Ruler quick action button to display or hide the ruler. When active, tap the ruler to hide it.