Evaluating DSM and its Origin Source: LiDAR or Photogrammetry

A quick look at Digital Surface Models and why you might choose one source over the other

When it comes to getting a clear picture of the Earth’s surface—whether you’re in insurance, utilities, solar, telecom, or transportation—Digital Surface Models (DSM) are a key dataset for solving problems and making informed decisions with valuable elevation information.

What elevation information are you after? The height of a building, vegetation encroachment near power lines, detailed outlines of roads or railways? DSMs provide a highly accurate 3D representation of the Earth, allowing for more detailed analysis to support better planning, risk assessment, and decision-making for multiple industries.

DSMs can be created from both LiDAR (Light Detection and Ranging) and photogrammetry sources. As a leader in aerial mapping and processing technology, Vexcel designs both photogrammetric and hybrid (photogrammetric and LiDAR) sensors, giving us deep expertise in the DSM products derived from these specialized sensors.

With this expertise, we’re offering insight and a comparison of LiDAR and photogrammetric DSM to help you answer a common question from customers around elevation data: what do I get with LiDAR or image-based DSM data and how can they best serve my needs?

Breaking Down How LiDAR and Image-based DSM Work

To better understand which source of elevation data you may choose to work with, it helps to first get a quick sense of how they are created. This piece focuses on data collected with fixed-wing aircraft and how both types provide a level of detail about what exists on the ground.

LiDAR – a remote sensing technology that uses light in the form of a pulsed laser to measure distances of various surfaces on the Earth

LiDAR

LiDAR is like painting the world with light, with lots of laser pulses scanning the ground to measure every peak, valley, road, and building with precision. It doesn’t just capture what’s on the surface—it reveals hidden details thanks to the multi-return aspect of the laser pulses, slicing through dense forests to expose the contours beneath, tracking coastal erosion with pinpoint accuracy, and detecting the subtlest changes in terrain. Scientists have even found lost cities in the thick Amazon rainforest using LiDAR technology.

The result is a rich 3D point cloud, a digital twin of reality, built with data instead of brushstrokes. And from this collection process, DSM is often a derivative product.

VEX-567-GRA-Illustrations-for-DSM-LiDAR-Blog-V3__DSM

Photogrammetric Digital Surface Model – 3D representation of all objects, vegetation, and features represented on the Earth’s surface

Photogrammetric DSM

Think of photogrammetric DSM like a patchwork quilt of images, with each aerial photo stitched together to create a seamless, high-resolution elevation map. Specialized software uses an algorithm called “dense image matching” which triangulates common points within these images, along with known sensor positions, to calculate the coordinate positions in 3D space, helping offer exceptional positional accuracy in the horizontal (x/y) and vertical (z) dimensions (depending on the quality of imagery used to derive the DSM). These common points help generate the detailed model that reveals the contours of the Earth’s surface, including buildings, vegetation, and trees.

This pixel-perfect elevation model mirrors the resolution of its source imagery, meaning the better the source, the more accurate the model. This makes it a powerful tool for seeing beyond the obvious—whether you’re mapping urban landscapes, understanding the height of an insured property, or optimizing telecom networks.

Key Benefits & Challenges of LiDAR and DSM

Both LiDAR and photogrammetric DSM (sometimes called PhoDAR) provide powerful elevation data, but each comes with its own benefits and trade-offs, some technical, some practical, and some financial. To break down the advantages and challenges of each, we gathered insights from Vexcel’s Head of Applied Photogrammetry, Bernhard Schachinger.

Schachinger explained that several key factors differentiate LiDAR-based DSM from image-based DSM. He emphasized that the most important considerations when determining how to use the data include the nature of the project, budget constraints, and the need for ongoing information to support decision-making. While both elevation types offer high-quality detail, understanding their differences can be critical to a project’s success.

LiDAR: High Accuracy with a Price

LiDAR is powerful. It cuts through tree canopy, maps fine details, and delivers stunning accuracy. But that precision comes at a cost, both financial and time.

Most LiDAR collection occurs at a lower altitude, meaning smaller swaths, more flight time. On average, it can be significantly more expensive than image-based DSM, meaning most organizations can only afford to update it once every 3-5 years—or more.

With the lower, slower flight times, it’s also harder to scale. And once it is collected, it can be slow to process with the filtering noise, point classification, and georeferencing.

LiDAR collected from a Vexcel UltraCam Dragon 4.1

Photogrammetric DSM: Complex Terrain and Source Quality

Image-based DSMs offer a level of detail and accuracy ready to inform many projects. More cost-friendly than LiDAR, image-based DSMs benefit from highly automated processing and are more easily integrated into many GIS platforms. Image-based DSMs can also be more frequently updated depending on the imagery it is derived from, such as Vexcel imagery. Vexcel DSM is derived from 7.5-15cm resolution imagery, helping users see structured details of objects, structures, trees, and vegetation.

The challenges of image-based DSMs revolve around density or complexity of the terrain. Unlike LiDAR, image-based DSMs can’t punch through dense vegetation to capture what’s beneath a tree canopy or support the ability to analyze extremely fine detail like utility pole wire drop.

An image-based DSM derived from a collection by a Vexcel UltraCam Osprey 4.1

Additional Comparisons of LiDAR & Image-based DSM

What other information is necessary to weigh when comparing DSM from LiDAR or image-based sources? Below are other key considerations to factor in when determining how to select elevation data.

Data & Accessibility

LiDAR often requires a custom flight and collection, making up-to-date data harder to acquire. Image-based DSM, on the other hand, is more widely available and frequently updated through ongoing aerial imagery programs like Vexcel’s, making it easier to obtain recent data.

Processing & File Size

LiDAR generates massive datasets due to dense point clouds, requiring specialized software and expertise to process. Image-based DSM datasets are less complex and typically lighter in file size (not always!) like off-the-shelf DSM from Vexcel, and easier to integrate or down sample into standard GIS and mapping applications; no need for additional processing.

Integration with Other Data

LiDAR pairs well with DEMs, contour maps, and 3D modeling applications, whereas image-based DSM is easier to use alongside ortho imagery, multispectral data, and 3D city models for visualization and analysis.

Cost of Ownership & Infrastructure

LiDAR requires significant investment in hardware, software, and processing capabilities. Some Vexcel Data Program customers say LiDAR collections can be 10 times more costly than image-based DSM. Photogrammetric DSM is more cost-effective since it leverages existing aerial imagery collections, reducing collection and processing costs.

Temporal Analysis & Change Detection

LiDAR excels at detecting terrain and structural changes over time, particularly in forestry, mining, and in particular, coastal erosion studies. Photogrammetric DSM is ideal for urban development tracking, construction monitoring, and disaster response due to its more frequent updates for surface changes.

Vexcel DSM and TrueOrtho images of a downtown commercial district

What Do You Need?

At the end of the day, what you select for your project really comes down to what you need and the parameters of your project, such as financial, visual, and practical applications.

LiDAR is for when you need to cut through the noise—super-fine terrain mapping, dense forests, precision modeling. Its ideal use cases are for specific autoclassification needs, topography, hazard assessment, and especially detailed flood analysis.

Photogrammetric DSM is for when you need highly automated processing, scale, and more frequently updated views of the world. Top use cases would include urban planning, property analysis, change detection, telecom, utilities management, disaster response, and infrastructure development.

Vexcel DSM and TrueOrtho images of freeway interchange in urban area

Can’t decide which to choose? Many customers are finding it necessary to augment their current LiDAR program with image-based DSM, helping fill in the gaps when they are between their scheduled LiDAR captures.

At the end of the day, both sets of data can deliver powerful information, according to Schachinger. And it was also one of the driving reasons behind the development of the UltraCam Dragon, Vexcel’s hybrid photogrammetric-LiDAR sensor as it delivers the best of both worlds.

A Customer’s Perspective: DSM in Action

Choosing the right elevation data isn’t just about sensor technology—it’s about getting answers faster and smarter. Some industries, like the utilities sector, need frequently refreshed imagery and elevation information to identify areas of change and to decide whether or not investment in LiDAR is warranted. This is where the power of updated image-based DSM can greatly impact how major companies look at their projects and manage their assets. Connor Valentine, PhD, of RedSynth, helps utilities and chemical plants analyze infrastructure using imagery and AI. As a former senior data scientist at FirstEnergy, he knows the challenges of managing assets at scale.

“The DSM dataset offered by Vexcel Data Program is incredibly powerful. Our clients are shocked by how quickly we can include height measurements in our analysis. Their history of height measurements goes years back in time, providing snapshots of height data for change detection or algorithms that learn over time.”

Connor Valentine, PhD.Partner at RedSynth

One of the biggest advantages? Vexcel’s DSM aligns seamlessly with its Ortho and Multispectral imagery, keeping elevation and imagery perfectly in sync. That means trusted, consistent data—no guesswork, no data shifts.

Some companies use photogrammetric DSM to supplement LiDAR collections, reducing costs while staying operationally sharp and informed. Other companies are finding they don’t need the high-fidelity of LiDAR and DSM will answer their questions. As Valentine puts it:

“Before you task a LiDAR collection, make sure your questions cannot be answered by using Vexcel’s DSM product. The lower cost enables ideas that simply would never be financially possible with current LiDAR prices.”

Vexcel DSM and TrueOrtho images of a property in Austin, TX

Vexcel DSM

Looking to add elevation data to your project mix? Vexcel offers high-resolution image-based DSM in 40+ countries around the world and is refreshed on a regular basis with a point density of 177 points/m² at 7.5cm spatial resolution (urban areas) and 44 points/m² at 15cm spatial resolution (urban and rural areas). In the U.S., Vexcel collects data which includes a DSM output up to twice a year in major metro areas, meaning DSM data could show shifts or changes when it comes to supporting urban planning and infrastructure development and line-of-sight analysis.

Learn More

Vexcel Data Program does not currently offer off-the-shelf LiDAR datasets, but we provide a rich archive of photogrammetric DSM data with ongoing updates. We can also connect you with on-demand LiDAR collectors if needed.

Interested? Fill out the form below to get a demo of your area and start using the high-resolution DSM data you need.

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