2D & 3D photogrammetry outputs explained (ideal for beginners!)

With geospatial software like Birdi, you can upload your GIS data and then process it into a variety of processed, photogrammetry outputs for visibility and insights about your sites, structures and locations. But if the world of photogrammetry is still relatively new to you, read on! We’ll give you an overview of the different outputs you can request within Birdi, how you might use them, and how they can benefit your business workflows and goals.

‍

What is photogrammetry?

‍

Photogrammetry is a versatile technology that can generate both 2D maps and 3D models from 2D images. Once you’ve captured your site imagery (ideally utilizing the correct capture approach) upload it into geospatial software like Birdi and request your processing outputs. From here, your individual images are stitched together and transformed into a range of outputs. In 2D, these are typically orthophotos/orthomosaics (top down, highly accurate maps corrected for distortions caused by camera perspective and terrain relief), and Digital Elevation Models (DEMS) and contours, which give 2D context about your site's terrain.  

‍

Photogrammetry can also create detailed 3D models of objects, landscapes, or entire scenes. In this process, Birdi analyzes the overlapping features in the captured images to reconstruct the geometry and texture of the subject in three dimensions. By triangulating points of commonality between the images, our processing engine calculates the position and orientation of each pixel in 3D space, ultimately generating a digital representation of the site with depth and spatial information. These 3D models can range from point clouds, which represent the surface geometry as a collection of points, to textured meshes, which include both geometry and realistic surface textures.

‍

We’ll explore these 2D and 3D outputs in greater detail below.

‍

3D photogrammetry outputs, their use cases and benefits

‍

Point Clouds

‍

A point cloud is a collection of points in a 3D coordinate system that represent the external surface of an object or scene. Each point in a point cloud corresponds to a specific location in space, capturing the geometry and spatial information of the scanned area. (Or said in a more basic way: Imagine taking a bunch of photos of an object or place from different angles. A point cloud is like connecting the dots between all the points in those pictures, creating a 3D shape). Compared to textured meshes (up next) point clouds lack surface and texture information. 

‍

‍

Use cases of Point Clouds:

‍

• Asset inspection and monitoring: Detailed inspection and monitoring of assets such as buildings, bridges, and industrial facilities, allowing for condition assessment, structural analysis, and maintenance planning.
• Construction: Monitoring progress and detecting deviations from plans by comparing Point Clouds with building designs.
• Urban planning: Assessing infrastructure and planning developments by analyzing the existing environment through point cloud data.

‍

Benefits of Point Clouds:

‍

• High precision: Point Clouds provide detailed spatial information, allowing for accurate measurements and analysis.
• Non-invasive: Point clouds enable you to capture data without physically touching an object or site, preserving delicate structures or environments.

‍

Textured Meshes

‍

A textured mesh is a collection of vertices, edges, and faces that define the shape of a 3D object. It represents the surface geometry of an object or scene, forming a solid structure composed of interconnected polygons. Textured meshes are overlaid with photographic textures, providing a realistic visual representation of objects or scenes. Textures are applied to the surface of the mesh, enhancing its appearance with detailed imagery captured during the photogrammetry process.

‍

‍

Use cases of Textured Meshes:

‍

• Construction: Construction progress can be monitored by comparing textured meshes at different project stages, along with providing highly detailed visual representations for quality assurance.
• Utilities: With detailed 3D representations of infrastructure, utilities companies can visualize asset locations, conditions, and surrounding environments for effective maintenance and planning.
• Facilities and Maintenance: Textured meshes facilitate space planning and management by providing detailed 3D representations of buildings and facilities. 

‍

Benefits of Textured Meshes:

‍

• Realistic visualization: Meshes accurately represent the surface geometry of objects, providing visually appealing and realistic models.‍
• Detailed surface information: Textured meshes combine geometric detail with surface textures, allowing for detailed analysis of surface characteristics, such as material properties, color variations, and surface roughness.‍
• Enhanced communication: Textured meshes facilitate effective communication and collaboration by providing intuitive visualizations that are easy to understand and interpret, enabling stakeholders to convey complex spatial information and ideas more effectively.

‍

When would you use a Textured Mesh compared to a Point Cloud?

‍

Both outputs are 3D models, but they serve different purposes and are used in different contexts depending on the specific requirements of a project.

‍

Visualization:

‍

• Textured Mesh: If you need a highly realistic and visually appealing representation of an object or scene, a textured mesh is often the preferred choice. Textured meshes provide detailed surface textures and colors, making them ideal for visualizations, presentations, and marketing materials where realism is important.
• Point Cloud: Point Clouds are more suitable for analytical tasks and technical applications where visual aesthetics are less critical. While Point Clouds accurately capture the spatial geometry of an object or scene, they lack surface textures and colors, making them less visually appealing for non-technical audiences.

‍

Digital twins and virtual environments:

‍

• Textured Mesh: Textured Meshes are commonly used to create digital twins and virtual environments that replicate real-world objects or scenes with high fidelity. 
• Point Cloud: Point clouds can also be used to create digital twins and virtual environments, however, they don’t provide the same level of realism as textured meshes. Depending on the use case, both are useful for producing digital twins. 

‍

Surface analysis and measurement:

‍

• Textured Mesh: Textured Meshes are useful for surface analysis and measurement tasks that require detailed geometric information combined with surface textures. For example, in construction or building maintenance, Textured Meshes can be used to analyze the surface characteristics of building facades to assess surface conditions in detail.
• Point Cloud: Point Clouds are commonly used for precise surface analysis and measurement tasks, such as calculating distances, volumes, and angles between points. Point Clouds provide accurate spatial data without the additional complexity of surface textures, making them well-suited for quantitative analysis and measurement applications.

‍

2D photogrammetry outputs, their use cases and benefits

‍

Orthomosaics/Orthophotos

‍

An orthomosaic, short for orthophoto mosaic (at Birdi, we use orthophoto and orthomosaic interchangeably), is a high-resolution composite image created by stitching together multiple aerial photographs of an area. Unlike traditional aerial photographs, which may suffer from distortions due to camera perspective and terrain variations, orthomosaics are geometrically corrected to remove such distortions, resulting in images with consistent scale and minimal distortion across the entire area.

‍

‍

Use cases of orthophotos:

‍

• Mining and resources: Having an accurate, top down visual representation of mining and quarry sites enables effective planning, monitoring and analysis.
• Environmental analysis: Assessing land cover and changes over time by comparing orthophotos captured at different intervals, aids in habitat conservation and natural resource management.
• Construction: Orthophotos provide up to date visibility of sites, and enable effective progress reporting by comparing maps over different time periods.

‍

Benefits of orthophotos:

‍

• Accuracy: Orthophotos provide precise measurements for analysis and planning, enabling informed decision-making and resource allocation (Birdi’s annotation tools are made for measuring areas and distances on orthophotos).
• Efficiency: Orthophotos provide up-to-date visibility which reduces the need for field visits, saving time and resources in data collection and surveying efforts.
• Insights: Provides up-to-date insights about sites and assets, enabling improved decision-making, workflows and insights.

‍

Digital Elevation Models (DEMs)

‍

A Digital Elevation Model (DEM) is a digital representation of the Earth's surface, depicting elevation data across a geographic area. (Elevation data refers to information about the height or altitude of points on the Earth's surface relative to a reference point, typically sea level. In comparison to orthophotos, which don’t contain any elevation information). 

‍

There are two main types of Digital Elevation Models (DEMs): Digital Terrain Models (DTMs) and Digital Surface Models (DSMs).

‍

Digital Terrain Models (DTMs)

‍

DTMs represent the bare earth terrain surface by removing above-ground features such as buildings, vegetation, and infrastructure. DTMs provide an accurate depiction of the natural topography, including hills, valleys, and landforms, without incorporating any surface features. 

‍

‍

Digital Surface Models (DSMs)

‍

DSMs represent the Earth's surface as it appears with all above-ground features included, such as buildings, vegetation, and other structures. DSMs provide a comprehensive view of the terrain's surface, including both natural and man-made features.

‍

‍

Use Cases of DEMs:

‍

• Topographic mapping for engineering and land management projects.
• Hydrological modeling for watershed analysis and floodplain mapping.
• Environmental studies for habitat mapping and terrain stability assessments.

‍

Benefits of DEMs:

‍

• Accurate representation of terrain elevation for precise analysis.
• Consistency in elevation data across large areas for reliable mapping.
• Easy interpretation and visualization for effective decision-making.

‍

Contours

‍

Contours are lines that connect points of equal elevation on a DEM (they are derived from the elevation information within a DEM). Contours represent the shape and elevation of the terrain in a two-dimensional format, providing a valuable tool for visualizing and understanding the topography of an area.

‍

‍

Use cases of Contours:

‍

• Topographic mapping: Contours are extensively used in topographic mapping to represent the elevation profile and terrain features of an area accurately.
• Land surveying: Contours serve as a fundamental component of land surveying, enabling professionals to determine land elevations, slope analysis, and site planning.
• Engineering design: Contours are essential for engineering design projects such as road construction, drainage design, and slope stability analysis, providing critical information for project planning and implementation.

‍

Benefits of Contours:

‍

• Visual representation: Contours offer a clear and intuitive visual representation of terrain elevation, allowing users to interpret the topography of an area at a glance.
• Elevation analysis: Contours enable precise elevation analysis, facilitating the identification of high points, low points, ridges, valleys, and other terrain features.
• Slope calculation: Contours provide information about slope gradients and steepness, supporting slope analysis and terrain modeling for various applications, including landslide risk assessment and infrastructure design.

‍

—

‍

Photogrammetry outputs offer a wide range of applications and benefits across various industries, from streamlining construction processes to supporting environmental conservation efforts. We hope understanding the different types of 2D and 3D outputs you can request and why you’d use one over the other can assist you in your GIS workflows. If you’d like to explore how you can use photogrammetry in your business, reach out to us and we can explore your needs and goals.

‍