Digital Surface Model vs Digital Elevation Model: A Guide
Before you can accurately map what’s underground, you need a reliable picture of the ground itself. Any plan for excavation or subsurface utility mapping starts with understanding the surface topography. An error in your surface data will create a ripple effect, leading to incorrect depth calculations and a greater risk of utility strikes. That’s why the choice between a digital surface model vs digital elevation model is so important. One model includes surface clutter like buildings and vegetation, while the other provides a clean, bare-earth view. This article will help you choose the right foundational data to ensure your subsurface work is safe and precise from the start.
Key Takeaways
- Know the difference to avoid errors: A Digital Surface Model (DSM) includes all surface features like buildings and trees, making it useful for line-of-sight analysis. A Digital Terrain Model (DTM) shows only the bare ground, which is critical for accurate grading, drainage, and excavation planning.
- Layer models for a complete picture: Get the most accurate site data by using both models together. Subtracting the DTM (bare ground) from the DSM (surface features) lets you calculate the exact height of trees and buildings, which is essential for logistics and clearance planning.
- Remember that data requires processing: Raw elevation data is not plug-and-play. It requires expert processing to filter out noise and create a clean, reliable model, ensuring your project plans are built on an accurate foundation.
What Are DSM, DEM, and DTMs?
When you start working with site data, you’ll quickly run into a trio of acronyms: DSM, DEM, and DTM. While they all sound similar, each one represents a different way of looking at a project site’s topography. Understanding the difference is key to making sure you’re using the right data for your job, whether you’re planning a new build, assessing environmental risks, or preparing for excavation.
Think of these as different layers of a map. One shows you every single feature on the surface, another strips everything away to reveal the bare ground, and the third is a general term that can refer to either. Let’s break down what each model does and why it matters for your project. Getting this right from the start saves a lot of headaches and ensures your plans are built on a solid, accurate foundation.
What is a Digital Surface Model (DSM)?
A Digital Surface Model (DSM) gives you a top-down view of the Earth’s surface that includes everything on it. Imagine you’re flying over your project site in a helicopter. The DSM is what you’d see. It captures not just the ground but also all the natural and man-made features, like buildings, trees, vegetation, and power lines.
This model provides a comprehensive picture of the landscape as it currently exists. Because it includes the heights of all objects, it’s incredibly useful for tasks like urban planning, line-of-sight analysis for telecommunications, and vegetation management. It shows you the world with all its features intact, giving you a real-world view of the surface.
What is a Digital Elevation Model (DEM)?
The term Digital Elevation Model (DEM) is a bit of a catch-all. It’s a broad category that refers to any 3D model of a terrain’s surface. Both DSMs and DTMs are technically types of DEMs. Because the term is so general, it’s important to clarify exactly what kind of data you’re looking at when someone mentions a DEM.
Is it a "bare-earth" model showing only the ground, or does it include all the surface features? Knowing the answer is critical for accurate analysis. Think of "DEM" as the parent category, with DSM and DTM as the two more specific, and often more useful, children.
Where Does a Digital Terrain Model (DTM) Fit In?
A Digital Terrain Model (DTM) is the opposite of a DSM. It represents the "bare earth" surface, which means it digitally removes all the buildings, trees, and other objects to show you just the ground itself. This model is essential when you need a clear and accurate understanding of the site’s topography without any obstructions.
DTMs are the foundation for many types of analysis, including flood modeling, geological surveys, and infrastructure planning. For anyone involved in groundwork, from grading a site to performing subsurface utility mapping, the DTM provides the clean, unobstructed view of the terrain you need to plan effectively and safely.
DSM vs. DEM: What's the Real Difference?
When you’re looking at a 3D map of a project site, it’s easy to assume all elevation models are the same. But the small differences between a Digital Surface Model (DSM) and a Digital Elevation Model (DEM) can have a huge impact on your project’s accuracy, safety, and budget. Think of it this way: a DSM is like a detailed photograph of the landscape, capturing everything from the tallest tree to the peak of a roof. A DEM, however, is what you’d get if you could digitally strip away all those features, revealing the bare, true shape of the ground underneath.
Understanding which model to use is critical for making informed decisions on the ground. Whether you're planning for drainage, grading a site for new construction, or trying to avoid utility conflicts during excavation, choosing the right data type prevents costly rework and ensures your plans reflect reality. Using the wrong one can lead to miscalculations in water flow, incorrect volume estimates for earthwork, or even safety hazards. Let’s break down the core distinctions so you can feel confident you’re working with the right information for your specific project needs.
Surface Features vs. Bare-Earth Ground
The most straightforward difference between these two models is what they actually show. A Digital Surface Model (DSM) captures the Earth’s surface along with all the natural and built features on it. This includes treetops, building rooftops, power lines, and any other objects. It’s a top-down view of everything standing on the ground.
A Digital Elevation Model (DEM), on the other hand, represents the "bare-earth" terrain. It digitally removes all those surface objects to give you a clean look at the topography of the ground itself. This is crucial for understanding the true shape of the land without any obstructions, making it the go-to model for most geological and hydrological applications.
How the Data is Captured and Processed
Both DSMs and DEMs are typically created using the same technologies, like LiDAR (Light Detection and Ranging) or photogrammetry. The raw data collected by a drone or aircraft captures millions of points from the surface. The real difference comes down to the processing stage.
To create a DSM, the raw point cloud data is used to generate a model that reflects the highest points, which naturally include buildings and vegetation. To create a DEM, that same data goes through an extra filtering step. Sophisticated software identifies and removes all the non-ground points, leaving only the data that represents the bare earth. This filtered data is then used to create a model of the true ground surface.
Why Accuracy and Resolution Differ
Because a DSM includes surface clutter, using it for the wrong task can lead to serious errors. For example, if you’re trying to model how water will flow across a site, a DSM would show buildings and dense tree canopies as high-elevation areas that block the flow, giving you a completely inaccurate result. Your drainage plan would be based on flawed information.
A DEM provides a much more precise view of the natural terrain, which is essential for applications like flood modeling and infrastructure planning. By removing the "noise" of surface objects, a DEM ensures that your analysis of slope, aspect, and water flow is based on the actual shape of the ground. This level of accuracy is critical for grading plans, pipeline routes, and any project where understanding the true topography is non-negotiable.
How Are Elevation Models Created?
Creating a detailed elevation model is a multi-step process combining aerial data collection with on-the-ground validation. Specialists use advanced technologies to gather millions of data points and then process them into an accurate 3D map. The primary methods for capturing this data are LiDAR, photogrammetry, and ground surveys. Each technique has its own strengths depending on a project’s goals and required level of detail. Let's look at how each one works.
Using LiDAR for High-Resolution Mapping
LiDAR (Light Detection and Ranging) is a remote sensing method that uses laser pulses to measure distances to the Earth's surface. A sensor, often on a drone or aircraft, sends out rapid laser beams and measures the time they take to bounce back, creating a dense cloud of data points. This technology is incredibly efficient for mapping large areas quickly. To create a DEM, software filters out non-ground points like trees and uses interpolation algorithms to connect the remaining ground points, forming a precise model of the bare-earth terrain.
Using Photogrammetry and Satellite Imagery
Another common method is photogrammetry, which involves taking overlapping photographs of an area and using software to stitch them into a 3D model. This technique is often used with drones to create detailed Digital Surface Models (DSMs) because it captures everything visible from the air, including buildings and vegetation. For broader views, Digital Elevation Models can also be generated from satellite imagery. While cost-effective, the accuracy of photogrammetry can be affected by shadows or dense forest cover, which can obscure the true ground level.
The Role of Ground Surveys and Data Processing
Aerial data alone doesn't guarantee accuracy, which is why ground surveys are a critical part of the process. Field crews use GPS equipment to collect precise elevation points on the ground, which are then used to validate and calibrate the data gathered from the air. This "ground-truthing" step ensures the final model is a true representation of the site. Once all data is verified, it’s fed into processing software that generates the final 3D visualization. This is where our team's expertise in subsurface utility mapping becomes essential for creating a complete site picture.
When to Use a Digital Surface Model (DSM)
A Digital Surface Model is your go-to when you need a complete picture of a site, including everything on it. Think of it as a 3D snapshot of the "as-is" environment. While a DEM shows you the bare earth, a DSM includes all the natural and man-made features sitting on top of it: buildings, trees, utility poles, and other structures. This makes it incredibly useful for projects where above-ground objects directly impact your plans.
If you’re trying to understand how a new building will fit into a cityscape, assess vegetation overgrowth, or map out signal paths for telecommunications, a DSM provides the real-world context you need. It captures the top-most surfaces of everything the sensor can see, giving you a detailed model of the current landscape. This data is fundamental for accurate planning, especially in complex or developed environments where surface features can create obstacles or opportunities for your project. For anyone involved in site development or environmental management, a DSM offers a layer of detail that a bare-earth model simply can’t provide. It answers the question, "What is actually on the surface right now?" which is critical for making informed decisions before excavation or construction begins.
Planning in Urban Environments
When you're working in a city or a developed area, the ground is rarely your only concern. A DSM gives you a highly accurate picture of the surface with all its features, which is essential for urban planning and visualizing how new construction might look. It maps out buildings, overpasses, and other structures, allowing you to run simulations for things like line-of-sight or shadow casting from a proposed building. This helps you see how a new development will interact with its surroundings before you ever break ground. By combining this above-ground data with a clear map of what’s below, you get a comprehensive view for safer, more efficient project planning.
Analyzing Vegetation and Forest Canopies
DSMs are perfect for any project involving vegetation management. Because the model captures the top of the tree canopy, it provides precise height measurements that are critical for understanding forest structure. Environmental consultants and land managers use this data to calculate biomass, monitor forest health, or assess wildfire risk by identifying areas with dense overgrowth. For construction and utility projects, a DSM helps you plan routes that avoid clearing mature trees or identify vegetation that might interfere with overhead power lines. It gives you the information needed to work with the natural landscape, not against it.
Mapping Line-of-Sight for Telecom
For the telecommunications industry, a clear line-of-sight is everything. When planning the placement of cell towers or microwave relays, engineers need to know exactly what might block a signal. A DSM is the ideal tool for this because it includes every potential obstruction, from tall buildings to dense clusters of trees. Using a DSM allows for an accurate model of the line-of-sight for telecommunications networks. This helps companies design more reliable networks by placing equipment where it will have the strongest, most uninterrupted signal path, saving time and money on installation.
Monitoring Environmental Changes
Because DSMs capture a detailed snapshot of the Earth’s surface at a specific moment, they are invaluable for tracking changes over time. By comparing DSMs of the same location taken months or years apart, you can precisely measure things like coastal erosion, deforestation, or the volume of material in a stockpile. This makes them a powerful tool for environmental monitoring and land management. For site managers and environmental consultants, this data provides clear evidence of landscape changes, which is essential for reporting, compliance, and planning future interventions. Integrating this data into a GIS mapping project helps create a living record of your site.
When to Use a Digital Elevation Model (DEM)
A Digital Elevation Model is your go-to tool when you need a clear, unobstructed view of the ground itself. Think of it as a digital "bare-earth" map. By digitally removing all surface features like buildings, trees, and other vegetation, a DEM reveals the true shape of the terrain. This makes it incredibly valuable for any project where the natural landscape is the primary concern. If you need to understand how water will flow, how stable a slope is, or where to best place new infrastructure, a DEM provides the foundational data you need.
This model is created by processing raw data, often from LiDAR, to filter out anything that isn't the ground. The result is a clean and accurate representation of the earth's surface, which is essential for large-scale analysis and planning. For general contractors, engineers, and environmental consultants, using a DEM is a critical step in understanding a site before breaking ground. It helps you anticipate challenges and design solutions that work with the natural topography, not against it. This kind of subsurface utility mapping and terrain analysis is fundamental to safe and efficient project execution.
Assessing Flood Risk and Water Flow
When you need to predict how water will move across a landscape, a DEM is the best model for the job. Because it shows the bare ground without buildings or trees, it gives you an accurate picture of natural drainage paths, low-lying areas, and potential flood zones. This is crucial for flood modeling and stormwater management. An urban DEM that includes buildings can give you a false sense of security, as it might not show how water would pool and flow if those structures weren't there. A bare-earth model provides the precise view of the natural terrain needed for accurate infrastructure planning and risk assessment.
Analyzing Slope Stability for Geological Surveys
For anyone working in hilly or mountainous terrain, understanding slope stability is a matter of safety and structural integrity. A DEM is created by generating a mesh from ground points, which accurately represents the real-world ground model. Geotechnical engineers and geologists rely on this data to analyze slopes, identify potential landslide risks, and plan construction projects safely. By understanding the exact grade and shape of the terrain, you can design retaining walls, foundations, and roadways that are built to last and withstand the forces of nature. It’s an essential tool for preventing costly and dangerous structural failures.
Planning Infrastructure and Grading Terrain
Before you can build anything, you need a solid plan for the land itself. DEMs provide the accurate topographic data needed to plan major infrastructure projects like roads, pipelines, and new developments. The elevation data allows you to create precise maps that are vital for planning site grading and earthwork. Whether you’re leveling a plot for a new facility or designing a road that follows the contour of the land, a DEM gives you the information to calculate cut-and-fill volumes accurately. This helps you minimize costs, optimize your design, and ensure the final project sits correctly on the landscape.
Understanding Watersheds and Drainage
A DEM is fundamental to understanding how a watershed functions. By mapping the elevation, slopes, and flow paths of an area, you can see exactly where rainfall will collect and how it will drain. This information is invaluable for agricultural planning, environmental impact studies, and urban development. For example, you can use a DEM to design effective irrigation systems or plan drainage solutions that prevent erosion and runoff pollution. It allows you to work with the natural water cycle, ensuring your project is both sustainable and compliant with environmental regulations.
Using DSMs and DEMs Together for Better Insights
While it’s important to understand the difference between a Digital Surface Model and a Digital Elevation Model, the real magic happens when you use them together. Think of them as two layers of a map that, when combined, give you a complete, three-dimensional picture of your site. A DEM provides the foundational bare-earth topography, while the DSM adds the context of everything built or grown on top of it. This combined approach moves beyond simple elevation data to deliver powerful, actionable insights for your project.
By comparing and contrasting these two datasets, you can calculate the true height of surface features, create far more realistic models for environmental analysis, and even track how your site changes over time. This integrated view is essential for everything from detailed pre-excavation planning to long-term asset management. Instead of choosing one model over the other, the most effective strategy is often to leverage the strengths of both. This allows you to make more informed decisions, anticipate potential conflicts, and keep your project on track from the start.
Calculate the Height of Trees and Buildings
One of the most practical applications of using both models is calculating the exact height of objects on your site. The process is straightforward: by subtracting the bare-earth elevation of a DEM from the surface elevation of a DSM, you can isolate the height of every tree, building, and piece of equipment. The result is what’s known as a Canopy Height Model (CHM), which is essentially a map of above-ground features. This is incredibly useful for planning utility routes around vegetation, assessing clearance for cranes and other large machinery, or conducting line-of-sight analysis for communication equipment. It removes the guesswork and gives you precise vertical data for better site logistics.
Create More Accurate Flood Models
When it comes to understanding water flow and flood risk, a DEM is the essential starting point because it maps the actual ground where water will travel. However, relying on a DEM alone can be misleading. Water doesn't flow across an empty field; it interacts with buildings, roads, and other structures. By overlaying a DSM, you can see how these surface features will obstruct, channel, or divert water during a storm. This combination allows for much more realistic hydrological modeling, helping you accurately predict problem areas, design effective drainage systems, and develop robust emergency plans that account for the as-built environment.
Track Landscape Changes Over Time
Elevation models aren't just static snapshots; they are powerful tools for monitoring your site's evolution. By capturing DSM and DEM data at different points in time, you can create a clear record of change. This is perfect for tracking the progress of large-scale earthworks, calculating the volume of stockpiles, or monitoring soil erosion on a graded slope. For environmental projects, this temporal analysis can be used to document land use changes or measure the success of site remediation efforts. This data-driven approach provides an objective, measurable way to manage your site, verify contractor work, and maintain a complete history of your project's development.
Common Myths About Elevation Models
Elevation models are powerful tools, but they’re often misunderstood. Treating them as simple, one-size-fits-all maps can lead to inaccurate plans, unexpected site conditions, and costly rework. When you’re planning an excavation or designing new infrastructure, a small error in elevation data can have a massive ripple effect. It can mean the difference between a smooth project and one plagued by change orders and budget overruns. Let’s clear up a few common myths so you can use these models with confidence and avoid some of the most common pitfalls.
Think of this as your guide to getting the most out of your data. By understanding what these models can and can’t do, you’ll be better equipped to ask the right questions, choose the right tool for your project, and ensure your subsurface data is as reliable as possible. Getting this right from the start saves time, money, and a lot of headaches down the road. We'll look at why not all models are created equal, why the data isn't just plug-and-play, and why you can't assume accuracy is consistent across your entire site. This knowledge will help you make better decisions and keep your projects on track.
Myth: They're All the Same
It’s easy to see why this myth persists. The term Digital Elevation Model (DEM) is often used as a catch-all for any 3D representation of a surface. In reality, DEM is a general category that includes two very different models: Digital Surface Models (DSMs) and Digital Terrain Models (DTMs). A DSM captures the elevation of everything on the surface, including buildings, vegetation, and other structures. A DTM, on the other hand, represents the bare-earth terrain with all those features stripped away. Using one when you need the other can completely derail a project. For example, planning a drainage system using a DSM would give you a water flow analysis based on rooftops and treetops, not the actual ground.
Myth: The Data is Plug-and-Play
Wouldn't it be nice if you could just download an elevation model and get straight to work? Unfortunately, it’s not that simple. Raw data from sources like LiDAR or photogrammetry comes in the form of a point cloud, which is just a massive collection of data points. This data requires careful point cloud processing by a trained technician to filter out noise, classify features, and generate a clean, accurate model. The quality of the final DSM or DEM depends entirely on the quality of the initial data capture and the skill applied during processing. It’s a classic "garbage in, garbage out" scenario, which is why working with experts who deliver field-ready data is so important.
Myth: Accuracy is Guaranteed Everywhere
Another common mistake is assuming that an elevation model has uniform accuracy across the entire project site. The reliability of the data can vary significantly depending on the environment. In a dense urban area, a DSM might struggle to capture the true ground elevation between tall buildings, creating "data shadows." Similarly, thick forest canopies can make it difficult for sensors to penetrate and map the ground below for a DTM. This is critical when you’re planning work that requires precise ground-level information, like trenching for new fiber or performing subsurface utility mapping. Always consider the site conditions and the model’s limitations before breaking ground.
Understanding the Limitations of Each Model
Elevation models are incredibly powerful tools, but they aren't flawless. Knowing their limitations helps you choose the right one for your project and interpret the data correctly. A model that works perfectly for a wide-open field might give you headaches in a dense urban core. The key is to understand where each model shines and where it might fall short, so you can account for potential inaccuracies before they impact your plans.
This awareness is especially important when you’re dealing with subsurface projects. An error in the surface data can lead to miscalculations for underground utility depths, drainage plans, and excavation safety. Let’s break down the common challenges you might face with both DSMs and DEMs.
DSMs: Challenges in Dense Environments
A Digital Surface Model (DSM) maps the top of everything it sees, from rooftops to treetops. It works by capturing the "first reflection" of a sensor, meaning it records the highest point it hits. While this is great for line-of-sight analysis or vegetation mapping, it creates real problems in crowded environments. In a city, a DSM will show you the height of buildings, not the street level between them. In a dense forest, it will map the canopy, completely obscuring the ground underneath. This can make it difficult to get a true sense of the underlying terrain, which is critical for accurate site planning and grading.
DEMs: Challenges with Data Filtering
A Digital Elevation Model (DEM), on the other hand, aims to show you the "bare earth" by digitally removing all those surface objects like buildings and trees. This filtering process is what gives you a clean look at the terrain itself. However, the filtering isn't always perfect. In areas with complex topography or thick vegetation, the software can struggle to tell the difference between a dense cluster of trees and a small hill. This can lead to artifacts in the data or accidental removal of natural ground features, which could affect everything from flood modeling to geological assessments. You can find more technical differences between DEM, DSM and DTM if you want to dig deeper.
Factoring in Cost, Time, and Technical Needs
Beyond the technical challenges, practical project constraints also play a big role. Generally, creating a highly detailed DEM is more complex and therefore more expensive than generating a basic DSM. The extra processing required to filter out surface features and correct for anomalies takes time and specialized expertise. You’ll also need the right tools for the job. While many point-cloud processing software packages can generate these models, the choice can impact your budget, timeline, and the technical skills your team needs. It’s important to weigh these factors early on to ensure you get the data you need without derailing your project.
Choosing the Right Model for Your Subsurface Project
When you’re planning to dig, the data you start with can make or break your project. Choosing between a DSM, DEM, or DTM isn’t just an academic exercise; it’s a critical decision that impacts your budget, timeline, and crew’s safety. The right model gives you a clear, accurate foundation, while the wrong one can lead to costly surprises and dangerous mistakes.
Think of it as the digital equivalent of a site walk. A detailed elevation model helps you see the terrain for what it truly is, allowing you to plan your excavation with precision. By understanding the ground’s surface before the first shovel hits the dirt, you can anticipate challenges, validate the location of underground assets, and create a safer work environment for everyone involved. This is where combining advanced mapping with expert subsurface utility mapping becomes essential for a successful project.
Improve Pre-Excavation Planning
Before you can map what’s underground, you need a reliable picture of the ground itself. For pre-excavation planning, a Digital Terrain Model (DTM) is often your best tool. A DTM provides a “bare-earth” view, digitally removing all buildings, vegetation, and other surface structures. This gives you an unobstructed look at the natural topography of your site.
Why does this matter? Because it allows you to accurately assess the ground’s slope, grade, and drainage patterns. With a clean DTM, you can plan site grading, design access roads, and identify potential water runoff issues without the visual clutter of existing structures. It’s the clean slate you need to build a solid and effective excavation strategy from the ground up.
Validate Utility Locations with Certainty
Once you have your surface mapped, the next step is to integrate the subsurface data. A Digital Elevation Model (DEM) serves as the foundational 3D grid of your terrain. When you overlay this with the precise location data gathered from GPR and EM scans, you get a complete picture of your site, both above and below ground.
This combination is crucial for validating the exact position and depth of buried utilities. It’s not enough to know a pipe is there; you need to know how its depth relates to the surface elevation at every point along its path. By integrating data from a private utility locating service with an accurate DEM, you can visualize how a utility line runs across a slope or dips into a trench, ensuring your excavation plan accounts for every variable.
Enhance Site Safety and Manage Risk
Ultimately, the goal of any subsurface project is to get the job done without incident. Using the correct elevation model is a fundamental part of risk management. For instance, relying on a model that includes building heights when you need ground-level data can lead to critical miscalculations in excavation depth, putting your crew at risk of striking a utility line.
In dense urban environments, a DTM offers a more precise view of the actual terrain, which is vital for planning infrastructure work around existing structures. By stripping away the buildings, you eliminate a major source of potential error. This level of accuracy ensures your team isn’t digging blind. They know what to expect, where to dig, and what to avoid, dramatically reducing the chances of a costly and dangerous utility strike.
Frequently Asked Questions
So, which model is actually better for my project? It’s less about one being "better" and more about which one is right for the specific task. If you need to see how a new building will fit into the existing cityscape or map out vegetation, a Digital Surface Model (DSM) is your tool. But if you’re planning any kind of groundwork like grading, drainage analysis, or preparing for excavation, you need a Digital Terrain Model (DTM) for its clean, bare-earth view.
What's the real difference between a DEM and a DTM? This is a common point of confusion. Think of Digital Elevation Model (DEM) as a general, umbrella term for any 3D model of a terrain. Both a DSM and a DTM are types of DEMs. However, in professional circles, people often use "DEM" and "DTM" interchangeably to refer to the bare-earth model. The important thing is to always clarify whether you're looking at a model with surface features included or one without.
Can I just use a free tool like Google Earth for my elevation data? While free mapping tools are great for a quick visual overview, they don't provide the survey-grade accuracy required for professional projects. For tasks like excavation, utility locating, or engineering design, you need high-resolution, verified data. Relying on consumer-grade information can lead to serious miscalculations, creating safety risks and budget overruns.
How do these models help with finding underground utilities? An accurate elevation model provides the crucial "Z" coordinate, or the elevation of the ground surface. When our crews locate a utility, they capture its horizontal position (X and Y). By combining that with the elevation data from a DTM, we can create a true 3D map of your site. This allows you to see the precise burial depth of a pipe or cable as it runs across sloped terrain, which is essential for safe and effective excavation planning.
How can I tell if the model I have is a DSM or a DTM? The easiest way is to look at the visual details. If the 3D model shows the distinct outlines of buildings, roads, and the bumpy texture of treetops, you’re looking at a DSM. If it appears much smoother and only shows the natural hills, valleys, and contours of the ground, it’s almost certainly a DTM. If you're still unsure, check the metadata that came with the file, as it should specify the model type.