What are elevation isolines?

Elevation isolines, or isohypses, are lines on a map connecting points of equal elevation above sea level. These lines represent changes in elevation in the landscape, allowing you to visualize mountains, valleys, hills, and other relief features on a flat map. Visually, isolines help better understand the shape of the earth's surface, making maps more informative and clear.

Isolines are used to depict terrain on maps of various scales – from large regional maps to detailed topographic maps. The more closely the isolines are spaced, the more accurate and detailed the elevation changes become. Isolines make it easy to determine the slope of a terrain, the depth of valleys, and the height of mountain ranges.

How are elevation contours constructed?

To construct elevation contours, digital elevation models (DEMs) are used. These models represent the elevation data for each point on the Earth's surface. This data can be obtained using satellite imagery, aerial photography, laser scanning (LiDAR), and other geospatial data collection methods. For more information on where to find elevation data, see our article Open Sources of Relief Data.

The process of constructing contours typically involves several steps:

1. Data preparation – selecting an elevation model (e.g., SRTM, Copernicus DEM, ASTER GDEM).

2. Calculating elevation values ​​for each cell of the raster image obtained from the DEM.

3. Constructing contour lines that connect points with the same elevation values. This can be accomplished using interpolation algorithms or other mathematical methods.

Thus, elevation contours on a map show how the elevation of an area changes and help easily identify relief features.

Where are elevation contours used?

Elevation contours are used in a wide variety of areas where it is necessary to analyze or plan land use based on its shape. Here are some areas where contours play a key role:

Cartography: Elevation contours are used to create topographic maps that show the relief of the terrain. They also aid in creating thematic maps for various applications, from tourist route maps to navigational charts.

Hydrology: In hydrology, contours help determine drainage basins and water flow directions. They are an important tool for flood analysis, drainage system design, and erosion assessment.

Urban planning: In infrastructure planning, contours are important for the design of roads, bridges, and other structures in mountainous and hilly areas. They allow for accurate accounting of elevation changes and reduce construction costs.

Environmental studies: Contours are used to assess the influence of relief on vegetation, as well as to understand the distribution of ecosystems and their changes over time.

Agriculture: In agronomy, contour lines aid in irrigation planning, erosion risk assessment, and land use optimization.

Elevation contour lines provide crucial information for analytics and decision-making in these areas, helping improve the accuracy of planning and forecasting. Modern tools can be used to create contour lines and use them to solve real-world problems. For example, the GISCARTA platform offers a contour line widget that allows you to easily visualize and analyze elevation data, making the process more accessible and efficient.

The Elevation Isolines widget on the GISCARTA platform

To get started with the widget, you need to make it available on the toolbar. You can enable it in the Widgets section; it will appear as a spiral.

Isoline creation widget on the GISCARTA web mapping platform

The widget uses the GEBCO DEM, resolution 500 m, as the basis for plotting isolines.

Next, you need to configure the following parameters:
– the interval between lines

Setting up the isoline widget parameters: frequency

– units of measurement

Setting up the isoline widget parameters: units of measurement

Then you need to select the extent and click the Get button.

Ready-made isolines, constructed using the Isolines widget on the GISCARTA platform

After processing in the widget, the resulting layer can be added to your database.

Exporting a vector layer with isolines on the GISCARTA platform

Conclusion

Elevation contours remain one of the most visual and versatile methods for analyzing elevation data. Modern web tools such as GISCARTA allow you to work with contours without complex data preparation or specialized software.

Key Takeaways

Contour accuracy depends on the quality of the DEM.
Noise, errors, and insufficient resolution in the elevation model directly affect the shape of contour lines.

Contour interval must match the map scale.
The chosen interval defines map readability and analytical value more than maximum detail.

Global DEMs suit analysis, local DEMs suit design.
Global models work well for regional studies, while local or high-resolution data are needed for engineering tasks.

FAQ

Where should I start when creating contour lines?
Start with an open global DEM and choose a contour interval appropriate for your map scale.

Are open DEMs suitable for contour generation?
Yes, open DEMs are suitable for most tasks when their resolution and limitations are understood.

Do I need desktop GIS software to work with contours?
No, modern web tools and widgets allow contour creation and analysis directly in the browser.