Changing the Working Scale (e.g. from Real to HO) will only affect horizontal ruler measurement and the grid sizes.
The yellow grid lines in HO will be 0.1m apart instead of 10m in real scale.
The "z value" is the height and heights are
always measured in metres.
With grades the units used (metric or imperial) and the working scale (real, HO, etc) are not important as all grades are expressed as a ratio percentage - 1% will be a 1m rise over a 100m, or a 1 inch rise over a 100 inch run regardless of whether you are using real or HO scale.
In HO scale a track that runs from one yellow grid line directly to the next will be 0.4 ft or 4.8 inches long. To give it a 1% grade its height would need to increase by 0.048 inches or about 0.1m (10cm). In metric real scale a 1% grade over 10m (one grid square) would also need a rise of 0.1m (10cm).
So as a rule of thumb, a rise of 0.1m (10cm) per grid square (assuming the shortest distance between the grid lines) regardless of the working scale is about a 1% grade.
PS: I just confirmed this by experimenting with a new HO working scale baseboard and
- setting the Tool Options Grade value to 1%
- selecting the Track object in the Placement Tool
- laying a track from one yellow grid line to the next
The height of the endpoint on the end of the grade was 0.1m
The tip is to not worry about measuring height changes over set horizontal distances but to set the desired
Grade in the
Tool Options Palette regardless of whether you are using metric or imperial, or what working scale (real, HO, etc) you are using..