If you use digital maps, it’s important to understand key terms and concepts. In this blog, we explore the differences between digital elevation models (DEM), digital terrain models (DTM), and digital surface models (DSM).Key takeaways:
More and more organizations, in an ever-growing range of industries, are using geospatial data analysis today - according to analysis from Deloitte. By generating and analyzing detailed maps, you can gain valuable new insights into the places you operate in, and improve how your business delivers its services.
In this article, we’ll compare three related but distinct acronyms around elevation data that you will invariably encounter when working with GIS: digital elevation models (DEM), digital terrain models (DTM), and digital surface models (DSM). Although they share a lot in common, these three terms have specific meanings, and it’s vital to know how they differ.
DTM digital terrain model Oruro, Bolivia
GIS software can show layers of geographical information in vector or raster format. Each layer provides different kinds of information. Terrain is one of the most widely used and can be divided into digital elevation, terrain, and surface models. Let’s learn what they are and how they differ.
A digital elevation model (DEM) is a general term representing ground elevation above sea level. In a DEM, all surface features (trees, buildings, bridges, etc.) are stripped away, and only the ‘bare earth’ is represented.
A DEM will show you:
Elevation is usually represented by color. For example, elevations of 0-10 m above sea level might be blue, 11-20 m above sea level could be orange, 21-30 m above sea level could be red.
Depending on where you live, a digital terrain model (DTM) may be identical to a digital elevation model. However, businesses or GIS software may represent something slightly different in some countries.
If your organization differentiates between DEM and DTM, then the DTM will be a layer ‘on top’ of the DEM. It will show additional information that the ‘bare earth’ DEM might not represent, including things like:
A digital surface model (DSM) is a type of terrain that includes all features above the bare earth - both natural and man-made. It will include ground features such as buildings, infrastructure, trees, and vegetation. The layer will represent the height of all these features above the ground on which they stand.
Dig deeper: Our in-depth guide to digital surface models
DTM digital terrain model Vancouver
Despite meaning different things, the acronyms DEM, DTM, and DSM are often used interchangeably (particularly DEM and DTM). Unfortunately, there is no universal definition of these terms, and they can be used in different ways in different contexts.
This is confusing and can cause problems with communication, especially when people from different organizations are working together.
For example, imagine two companies are collaborating on a flood management project. Maria works for Company A, and understands DEM and DTM as synonyms for ‘bare earth’. However, she’s collaborating with Hans from Company B. For Hans, DTM means bare earth plus linear features such as roads.
These different interpretations could significantly impact how each company approaches the project. Hans would be looking at a map that shows important features such as roads, whereas Maria might ‘miss’ this key information. That would have a significant impact on how each company plans its part of the flood management project.
To avoid this kind of problem, it’s useful to:
How they’re made: Understand how LiDAR is used to create DEM and DSM models
Geographic Information Systems with DEM, DTM, and DSM layers are used in many industries for various reasons.
Very often, professionals will use multiple kinds of models at different stages of a project. For example, an architect might use a digital elevation model to understand the angle of a slope when planning the foundations of a building. They’ll then use a digital surface model to understand the lines of sight from their structure. The DSM could, for instance, help them see whether trees may block sunlight - this information wouldn’t be available in the DEM.
Here are some major uses of DEM, DTM, and DSM.
Digital elevation models and digital terrain models help you understand the ‘natural’ shape of the earth’s surface - without the ‘distraction’ of buildings, trees, or other infrastructure. DEMs and DTMs are especially useful for things like:
Digital surface models show you both ground elevation and the height of everything above it. This allows you to understand how ground features interact with one another and the bare earth. DSM’s are useful for things like:
Modern mapping technology is increasingly accessible, and organizations in a wide range of industries are now using DEM, DTM, and DSM models for all manner of purposes.
LuxCarta, a leading remote sensing company, has extensive expertise in extracting valuable information from the Earth's surface, including generating detailed Digital Elevation Models (DEMs), Digital Terrain Models (DTMs), and Digital Surface Models (DSMs) at various resolutions and accuracy levels. Whether you need high-resolution elevation data for flood risk analysis, detailed vegetation maps for 5G network planning, or accurate DSMs for creating realistic simulations, LuxCarta's team of experts can provide the data and services you need.
Contact LuxCarta today to learn how their advanced remote sensing solutions can support your specific requirements.