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The action sports field guide

Action sports,
explained.

From street sessions to mountain terrain, explore the gear, conditions and ideas behind BMX, snow sports, surfing and flight.

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Illustrated guides. Clear sources.

Latest illustrated guides

Read a specification, separate two forecast variables or work through a movement model. Our newest guides pair each question with original diagrams and worked comparisons.

  1. Weathered stone harbour steps descend into teal seawater, with wet stone bands and gentle ripples on the surface.
    Wind & Water

    Tide Height vs Tidal Range vs Current: Read Each Value

    Compare tide height, tidal range and current speed using datum and timing examples. Learn why high water cannot tell you when slack current occurs at a site.
  2. Touring skis lie base-up beside a rolled orange climbing skin, with the plush surface, ski edges and attachment hardware visible.
    Alpine & Snow

    Ski Skin Sizing: Width, Length, Trimming and Compatibility

    Size climbing skins for your exact ski: compare width, length, edge exposure and tip-tail attachments, then confirm compatibility before trimming or ordering.
  3. A pair of charcoal alpine skis with orange tips shows curved sidecuts, upturned tips, metal edges and bindings in a studio.
    Alpine & Snow

    Ski Sidecut Radius, Rocker and Effective Edge Explained

    Understand ski sidecut radius, camber, rocker and effective edge. Compare specification views and learn why a stated radius does not fix the size of each turn.
  4. Low clouds wrap a rocky alpine ridge beneath a higher summit with patchy snow, illustrating separate cloud and surface conditions.
    Alpine & Snow

    Mountain Forecasts: Freezing Level, Snow Level and Cloud Base

    Learn what freezing level, snow level and cloud base mean in mountain forecasts, how height references differ and why existing snow cover is a separate record.
  5. Ivory and amber skateboard wheels on a dark workbench show rounded urethane lips, riding surfaces and metal bearing seats.
    Urban & Gravity

    Skateboard Wheels: Diameter, Durometer and Contact Patch

    Compare skateboard and longboard wheel diameter, durometer, contact-patch width and profile. Read labels accurately and check what each specification leaves out.
  6. Parallel deep-blue ocean swell crests recede toward the horizon, with sunlight highlighting their curved surfaces.
    Wind & Water

    Wave Period and Wavelength: What Deep-Water Numbers Mean

    Convert wave period to wavelength with the deep-water formula. Compare crest and group speeds, check the depth assumption and follow clear worked examples.
  7. An orange-and-ivory paraglider with one seated pilot flies above a broad alpine valley and layered mountain ridges.
    Aerial & Elevation

    Paragliding Airspeed vs Groundspeed: How Wind Adds

    Compare paragliding airspeed and groundspeed with headwind, tailwind and crosswind examples. Learn how velocity vectors differ from a GPS speed reading.
  8. An aerial landscape extends from inland hills and fields to a distant coastline and sea horizon, showing contrasting terrain elevations.
    Aerial & Elevation

    Skydiving Altitude: MSL vs AGL and Density Altitude

    Compare MSL, AGL and density altitude in skydiving. Work through ground-elevation examples and see why terrain and altitude references must stay together.
  9. Side view of a charcoal BMX bike showing its frame triangle, high-rise handlebar and two wheels on a concrete studio floor.
    Urban & Gravity

    BMX Frame Geometry: Top Tube, Reach, Stack and Wheelbase

    Read BMX geometry charts by separating top-tube length, frame reach, stack and wheelbase. Compare reference points, missing dimensions and complete-bike setup.
  10. A vertical black-and-white river gauge is mounted to a stone bridge pier beside flowing water in a rocky channel.
    Wind & Water

    River Gauge Stage vs Discharge: Units and Rating Curves

    Understand river stage versus discharge, gauge-height units and station rating curves. Use worked examples to keep datum, location and time with each reading.

Use the numbers. Keep the observations.

A forecast comparison needs its units and wave labels. A bike fault needs a specific symptom. A clothing change needs a record of when it helped. These resources turn the guides into something you can work with.

Start with a practical question

Guides explain concepts and preparation. Follow each page's source notes, current equipment instructions and suitable practical training. Learn how we handle sources and corrections in our editorial standards.

Explore four reading collections

Urban & Gravity — representative discipline

Urban & Gravity

10 guides

Hard surfaces, street terrain, gravity lines.

Understand wheels, contact, shared-space etiquette and controlled movement before planning a street or park session.

 Alpine & Snow — representative discipline

Alpine & Snow

12 guides

Altitude, powder, rock and ice.

Prepare for changing mountain conditions, snowpack questions, outdoor climbing and the equipment used on the approach.

 Wind & Water — representative discipline

Wind & Water

12 guides

Waves, wind windows, current.

Read water and wind information, distinguish the roles of different rigs, and plan with the actual venue and equipment.

 Aerial & Elevation — representative discipline

Aerial & Elevation

10 guides

Thermals, cliffs, open spans.

Understand flight concepts, weather briefings and specialist training boundaries for aerial sports and highlining.

Work through a specific question

Start with forecast interpretation, an inspection record or an equipment diagram. Each guide keeps its source material separate from the editorial examples.

Parallel swell lines approaching a sandy coast at dawn with a surfboard resting above the waterline.
Wind & Water

How to Read a Surf Forecast: Height, Period and Direction

Decode surf forecast labels with worked component comparisons. Separate combined seas, swell period and direction, then keep a record using the Swell Component Lab.

 A BMX bicycle in a workshop with its front wheel and brake components visible beside inspection tools.
Urban & Gravity

BMX Pre-Ride Check: Wheels, Brakes and Bike Inspection

Organise a BMX pre-ride check and write a useful fault report. Download a reusable inspection log with clearly labelled fictional examples for a mechanic.

 An overhead arrangement of a base-layer top, fleece, waterproof shell, gloves and an insulated jacket.
Alpine & Snow

Mountain Layering System: Base, Midlayer and Shell

Plan clothing for ascent, stops and the return. Use a downloadable layering field log and a fictional worked record to separate garment, fit and packing problems.

 A kitesurfer on open water beneath a colourful power kite.
Wind & Water

Kitesurfing Wind Window: Power Zones and Apparent Wind

Understand the kitesurfing wind window, kite-position terminology and apparent wind. Learn what a diagram or wind-range chart leaves out of a real session.

 A surfer riding above the water surface on a board supported by a submerged hydrofoil.
Wind & Water

Hydrofoil Surfing Explained: Lift, Pitch and Foil Parts

Learn how a surf hydrofoil generates lift, what the mast and wings do, and why pitch, water flow and the complete setup matter more than area alone.

 A quiet concrete skatepark with helmeted riders waiting in separate areas beside clear riding lanes.
Urban & Gravity

Skatepark Etiquette: Taking Turns and Planning Lines

Learn skatepark etiquette for queues, shared lines, blind bowls and filming. Use a practical session example to choose where to wait, ride and finish.