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
✉️ Recommend to a friendMatch 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.