Slope angle tool
Navigator's Slope Angle Tool
Print this card, then lay it across the contour lines on your map to read the slope angle — useful for route choice and avalanche awareness. Because it's matched to real contours, it must be printed at true scale.
⚠️ Print at 100% (actual size) — turn OFF “Fit to page”. The card includes a 50 mm ruler: measure it after printing to confirm the scale is exact. Download the PDF (not an image) so the geometry stays true to size.
Contour interval
Match this to your map's contour spacing — it changes the line spacings. OS Explorer/Landranger are usually 10 m.
How it works
Contour spacing on paper = contour interval ÷ (scale × tan angle). Each group of lines is drawn at that exact spacing, so the group that lines up with your contours gives the angle.
Contour spacing on paper = contour interval ÷ (scale × tan angle). Each group of lines is drawn at that exact spacing, so the group that lines up with your contours gives the angle.
Preview only — sizes on screen depend on your display. The downloaded PDF is exact when printed at 100%.
Use of this tool is offered on the condition of a donation to Severn Area Rescue Association.