Start with the legend, not the line

Most walkers do the same thing: unfold the map, find the car park, and trace a path with a finger without ever reading the key. It is the map-reading equivalent of cooking a new recipe by skipping straight to the method. Before you follow a single green dash, spend five minutes in the legend, usually printed on the cover flap or in the corner.

Two things matter more than anything else there. The first is scale. On a 1:25,000 Explorer sheet, four centimetres on paper equals one kilometre on the ground; on a 1:50,000 Landranger it is two centimetres. That difference decides whether a walk feels like a gentle afternoon or a route with four extra miles hidden in the folds. The second is the edition date, printed near the legend. Paths get diverted, new permissive routes appear, and stiles vanish. A map more than a few years old is still useful, but it is a plan rather than a promise.

The green lines: what each right of way actually allows

In England and Wales, the coloured lines showing rights of way are not decoration — they tell you what you are legally entitled to do. Get this wrong and you may find yourself pushing a bike up a path where cycling was never permitted, or turning back at a bridleway gate that would have taken you happily onwards.

• Public footpath — short green dashes. Walking only, plus a dog under control or on a lead on most land. No cycling, no horses.
• Public bridleway — longer green dashes. Walkers, horse riders and cyclists, but cyclists must give way to walkers and riders.
• Restricted byway — green dashes crossed with small plus signs. As a bridleway, plus horse-drawn vehicles and some other non-motorised traffic.
• Byway open to all traffic — green dashes with larger crosses. Legally open to vehicles, though often no more than a muddy track in practice.

Look out too for permissive paths, usually shown as broken orange or brown lines rather than green. These are routes the landowner has kindly allowed the public to use. They are not public rights of way and can be closed at certain times of year, or withdrawn altogether. Delightful to find, worth checking before you build a whole day around one.

Access land, forests and the right to roam

Open access land appears on Explorer maps as a pale wash, often with a boundary shown by a distinctive line and an access symbol. This is land mapped under the Countryside and Rights of Way Act 2000, where you can walk freely away from paths. The same Act lets you roam on much common land and some downland, but access land is not a free-for-all: you must still respect closures, keep dogs on a short lead near livestock and between March and July on most access land, and stay out of gardens, farmyards and growing crops.

Scotland works differently. Since the Land Reform (Scotland) Act 2003, statutory access rights cover most land, provided you behave responsibly under the Scottish Outdoor Access Code. There, a map is less a list of permitted corridors and more a guide to sensible choices.

Watch for red flag symbols and danger areas marking military ranges and training land. Where a red flag is flying, access is closed, no argument and no shortcut.

Contours, distance and honest timekeeping

Contours are the map's way of telling you how much work your legs are in for. On a 1:25,000 sheet the interval is usually five metres, on a 1:50,000 it is ten. Tightly packed lines mean steep ground; a series of parallel lines running up a slope tells you there is a climb ahead, however pleasant the valley looks on paper.

A reliable rule of thumb is one hour for every five kilometres, plus one hour for every 300 metres of ascent — and it is the ascent, not the distance, that catches people out. Add more time for rough ground, bog, stiles, gates and the inevitable pauses to admire the view. A four-mile route over two hills can easily take longer than a flat seven-mile one.

Symbols that quietly save you trouble

Scan the line of your route for the small marks that change a walk's character. Fords and stepping stones may be impassable after rain. Tidal crossings need local tide times, not optimism. Hachures, the short black tick marks, mark cliffs and very steep ground. A green dashed line running over a white gap with no footbridge is a stream crossing you should look at closely before committing to it.

Boundaries cause confusion too. Black dashed lines may mark civil parish boundaries, not paths, and fences or walls drawn in black may have no gate on your route at all. Check where the gates, stiles and ladder stiles actually fall.

A five-minute check before you leave the house

• Confirm the scale, edition date and that the sheet covers your whole planned route with margin to spare.
• Trace the entire line, checking for footbridges, gates, fords and climbs.
• Estimate distance and ascent separately, then add a generous buffer.
• Note any access land boundary, permissive path or closure symbol on your route.
• Identify one obvious escape route or shortcut in case the weather turns.
• Take a compass and know the grid reference of your start and finish.

Read the map properly at the kitchen table and the walk itself becomes simpler: you spend your energy on the countryside rather than on second-guessing the paper in your hand.