Elevation Profile Tool

What a terrain profile is and what it is used for

A terrain profile, or long section, shows how ground elevation changes with distance along a route. The horizontal axis is the distance from the start (chainage) and the vertical axis is elevation. It is one of the first things to look at when planning a road, canal, pipeline, power line or fibre route: it shows where the route climbs, where the steepest stretch is and how much height is gained overall.

This tool extracts the elevation profile of a line you draw or load, entirely in your browser. It computes slope and ascent statistics and prepares a long-section DXF with a level and chainage table underneath, in the form design offices are used to. It is intended for route screening and for comparing alternatives.

How to use it

1. Press "Draw a Line on the Map", click the route vertices in order and click the last vertex again to finish. You can also load a KML, KMZ, GPX or GeoJSON file, or type the vertices as latitude, longitude pairs.
2. Choose a sampling interval. Points are taken at whole multiples of the interval along the chainage (for example 0+020, 0+040); with "add line vertices" on, the corners of the line are included as well.
3. Move the pointer over the chart to see the matching point on the map; moving along the line on the map selects the same point in the chart. The vertical exaggeration can be changed above the chart.
4. The summary lists horizontal and slope length, lowest and highest elevation, total ascent and descent, and mean and steepest slope. The table under the chart shows how much of the route falls into each slope class.
5. Pick horizontal and vertical scales and download the DXF section, the point list as CSV, the chart as PNG or the route with elevations as GPX.

The DXF long section

The DXF is written in AutoCAD 2000 format with the metre as drawing unit. Chainage is drawn at true length and elevation differences are exaggerated by the ratio of the horizontal to the vertical scale; at 1:1000 horizontal and 1:100 vertical the exaggeration is 10x. The ground line is on PROFILE_GROUND, level grid lines on PROFILE_GRID, ordinates at stations on PROFILE_ORDINATE, the table on PROFILE_TABLE and text on PROFILE_TEXT. The table gives ground level and chainage at every station, written vertically, with distance and grade between stations. The datum is rounded down to one grid step below the lowest level. The title block lists the scales, the start and end coordinates and the data source.

Data and method

Elevations are read at zoom level 14 from AWS Terrain Tiles (Mapzen/Tilezen), published as open data, using bilinear interpolation between the four surrounding pixels. In many regions, including Turkey, the underlying data comes largely from global models such as SRTM with a resolution of about 30 m. Distances are horizontal distances on the WGS84 ellipsoid computed with Vincenty's formulae. Slope is the elevation difference between two consecutive points divided by the horizontal distance. Lines can be up to 200 km long; if more than 5,000 points would be needed, the interval is increased and the tool tells you.

The chart runs on Chart.js 4.4.1 (MIT licence), KML and GPX parsing on @tmcw/togeojson 5.8.0 (BSD-2-Clause licence) and KMZ extraction on JSZip 3.10.1 (MIT licence); icons come from Lucide (ISC licence). Basemaps are provided by Esri and OpenStreetMap contributors. Open-source libraries used and their licences: Data Sources.

Accuracy limits

• Data resolution: The effective resolution of the source model is roughly 10-30 m. Road cuts, embankments, bridges, culverts, stream beds and slopes that change over short distances disappear or are smoothed. Sampling at 5-10 m adds no new detail; it only interpolates.
• Vertical accuracy: The SRTM mission specification set an absolute vertical accuracy target of 16 m at 90% confidence. Levels can be several metres off the true ground, so slopes computed over short stretches can be misleading.
• Buildings and trees: Radar-derived models are affected by rooftops and tree canopies. Through towns or forests the profile may follow the surface rather than the ground.
• Design and setting out: This profile must not be used for road, canal or pipeline design, vertical alignment, cut and fill quantities or setting out. It is for preliminary studies and rough planning.
• Survey for final work: At design stage the route must be surveyed in the field with a GNSS receiver or total station, or the section must be taken from a high-resolution model produced by drone photogrammetry.

For professional projects

Rodosto Teknoloji works on geospatial projects for transport and utility networks, from route data to asset management on GIS platforms. You can find more on the Rodosto Teknoloji website or reach the team through the contact page.