How 3D route maps are made

The raw landscape

A grid gives the computer a height at regular positions.

Digital elevation model is a broad term for a gridded representation of height. A digital terrain model usually aims to describe bare ground. A digital surface model can include the top of buildings, vegetation and other objects. The distinction matters because a tree canopy is not the trail beneath it.

Resolution describes the spacing between samples. Ordnance Survey's OS Terrain 5, for example, provides a terrain grid for Great Britain at 5 metre post spacing. Global datasets can have much wider spacing. Finer spacing can represent smaller landforms, but accuracy also depends on the sensor, processing, date, coordinate reference system and vertical datum.

From numbers to surface

Neighbouring height samples become connected triangles.

1. Clip

   Select the terrain around the route.

   The renderer takes a bounded area with enough surrounding ground to show valleys, ridges and context.

2. Project

   Convert positions into workable map units.

   Latitude and longitude are transformed into a local plane so horizontal distances and heights can be handled consistently.

3. Sample

   Read or interpolate the height grid.

   Missing values, water and tile edges need explicit treatment before the surface is continuous.

4. Connect

   Build a mesh.

   Adjacent grid points become vertices, and triangles join them into a surface a graphics processor can draw.

A renderer may simplify the mesh for speed, especially on a phone. It may also calculate slope direction, ambient occlusion or other supporting values before the finished scene is delivered.

Put the journey back

The route is projected, sampled and lifted onto the terrain.

GPX stores ordered route or track points with latitude and longitude, and can include elevation. The map transforms those points into the same local coordinates as the terrain. It then finds the surface height beneath each part of the line, either from the terrain model or from suitable route elevation data.

The visible line is normally raised by a very small amount so it does not flicker through the surface. Curves may be interpolated between the supplied points, and a dense track may be simplified to reduce rendering cost. These choices affect appearance without turning the line into a surveyed path boundary.

Make shape legible

Lighting and camera angle turn a mesh into a readable scene.

Surface normals tell the renderer which way each part of the mesh faces. A virtual light then creates highlights and shadows that reveal form. Colour can distinguish water, ground or route status, while atmospheric fade helps separate near and distant terrain.

The camera is part of the explanation. A low angle emphasises relief and route context; a high angle resembles a conventional map. Some visualisations exaggerate vertical scale so gentle terrain reads clearly on a small screen. When used, that is a display choice, not a claim that the slope is physically steeper.

Model, not ground truth

Detail below the data spacing may disappear.

• Small featuresA bank, wall, gully, rock step or narrow cutting can fall between elevation samples.
• Surface typeHeight data does not say whether the route crosses tarmac, mud, loose stone, vegetation or legal access land.
• TimeErosion, construction, landslip, forestry and water levels can change after the source data was captured.
• MeasurementGPS positions and elevation datasets carry their own uncertainty and may use different reference systems.
• PresentationSmoothing, simplification, shadows and vertical exaggeration can improve clarity while reducing literal appearance.

A 3D route map is a strong tool for seeing the journey in its landform. It is not a substitute for current mapping, route notes or observation outside.