Just curious as to what tools and techniques you use to measure grade?
It is rise over run. There is still ambiguity however, since it is not clear whether the run is the slant distance measured along the track or just the horizontal component of that. These two alternatives correspond to the sine and the tangent respectively of the angle that the track makes with the horizontal.
The AREMA (American Railway Engineering and Maintenance-of-Way Association) Manual for Railway Engineering does little to resolve the question. It defines “grade” as “The elevation difference between two points of the Absolute Vertical Space Curve a preselected distance apart”. But there is no clarification of how the “preselected distance” is measured, which is the crux of the problem.
Fortunately for railroading, the grades are so small that it doesn’t matter which definition you use, which is probably why the writers of the AREMA manual felt free to be so vague.
By the way, the use of the word “tangent” in a railroad context is problematical, since it generally is used to refer to a straight track (which is geometrically tangent to the curves at either end of it).
As for tools, a tape measure is about all you need.
And plus a level I’m sure.
You don’t need a level. You only need to know the rise over the distance in order to figure the grade. A 1 foot rise in 100 feet equals a 1% grade.
I have no idea how you would measure a grade without some level or similar tool.
You do need some way to measure height. If the layout is on any reasonable table, you can just measure it from the table. Otherwise, you could use the floor (or the ceiling) as a reference. Failing all this, you would need a level. You could use a water level (http://www.factsfacts.com/MyHomeRepair/WaterLevel.htm) or create a level surface near the track with a spirit level.
I recall a device made by the late Gordon Odegard who was a Model Railroader Magazine staffer years ago. It was a carpenters level with an adjustable leg on one end. There was an article about it in that magazine years ago. Also, Micro-Mark has a device in their catalog that measures the angle off plumb. That would be useful for measuring grade also. The greater the angle the steeper the grade.
George