The principle behind photogrammetry

If you walked around a building and took digital photos from lots of different angles, each image would capture a slightly different view. Photogrammetry software compares these different images, identifies common features across them, and uses this information to calculate their precise position.

A useful way to think about it is comparing it to how people see the world. Each of our eyes sees a slightly different view and our brain combines them to create depth. Photogrammetry does the same thing, but instead of two images, it might use hundreds or even thousands.

The three key steps involved in the photogrammetry process

While the process is highly technical behind the scenes, it can be broken down into three main stages:

1. Understanding the camera

Before anything else, the software needs to understand how the camera “sees” the world. Every lens introduces small distortions, so the system accounts for these to ensure measurements are accurate. This step is often called camera calibration.

2. Matching images and building the model

Next, the software searches across all the photos to find matching features, points that appear in multiple images.

By linking thousands of these points together, it builds a 3D framework known as a point cloud. This forms the foundation of the final model.

3. Placing it in the real world

Finally, the model is tied to real-world coordinates using surveyed control points.

This step, known as georeferencing, is what turns a visual model into accurate, usable survey data that designers and engineers can rely on.

Why overlap matters in photogrammetry

One of the most important requirements in photogrammetry is image overlap. Each digital photo must share a significant amount of common ground with the next, typically 60-80%. If there isn’t enough overlap, gaps can appear in the data, accuracy is reduced and the final model may be unreliable. So, good data capture is just as important as good processing.

Why this matters for clients

Understanding the basics helps you ask the right questions and ensures you get data you can trust.

The process may happen behind the scenes, but the impact is huge. The quality of the final output depends on professional planning, coverage, and control, not just the software used.

Photogrammetry is now more accessible than ever, but producing reliable, accurate survey results still requires professional expertise.

For detailed guidance on workflows, accuracy, and specifying photogrammetry surveys, download the full client guide from The Survey Association website.

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Driving professional excellence

The Survey Association provides a dynamic and forward-thinking community where organisations can collaborate, share expertise, and collectively raise standards across the profession. Membership of TSA demonstrates commitment to quality and signals that your organisation consistently performs to the highest professional standards and adheres to best practice.

Network, collaborate and grow when you join The Survey Association

One of the most valuable aspects of TSA membership is the opportunity to connect with like-minded professionals across the geospatial sector. Members enjoy a packed calendar of networking opportunities throughout the year, including:

• Exclusive events at prestigious venues such as Wembley, Twickenham, and Silverstone
• Inspirational guest speakers
• Informal and formal opportunities to build relationships and collaborate

These events are powerful platforms for learning, sharing ideas, and building lasting business connections.

Invest in your team with CPD and training

Continuous professional development is essential in maintaining high standards and keeping pace with change across the construction industry. TSA supports this by offering:

• Access to valuable CPD opportunities
• Discounts at The Survey School, helping to train and develop talent
• Reduced rates on software licences from Leica,Trimble and Topcon
• PI Insurance scheme tailored to TSA members

Membership that fits your organisation

Whether you are a small specialist team, a large surveying firm, or involved in the wider geospatial world, TSA offers a range of membership levels to match your eligibility so you can access the correct category for your business.

Raising the profile of geospatial surveying

At a time when the role of geospatial has never been more important, TSA is leading a national marketing campaign to reposition surveying as a strategic, indispensable function within the construction industry. The campaign champions the value of geospatial surveying and elevates the profession as a whole.

If you want to strengthen your professional credibility, build meaningful connections and support the future of geospatial surveying, find out more about how to join TSA today. https://www.tsa-uk.org.uk/about-tsa/contact/

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The conversation should be all about what spatial evidence clients need, in order to make the right decision.  A unified national campaign is underway to help reposition geospatial surveying from a technical support service to a critical evidence-based profession.

Client Guides: a practical resource for professionals and clients

TSA’s Client Guides are not intended to overwhelm with highly technical details, but instead they provide concise, accessible introductions to a wide range of surveying disciplines. If you’re an architect, engineer, planner, project manager or simply a client looking to understand what you need and why, these guides offer a great starting point.

Each guide is carefully structured to answer the questions you’re most likely to ask:

• What is this type of survey?
• When and why is it needed?
• What equipment and techniques are used?
• What regulations or procedures apply?

This practical approach helps demystify surveying, giving you confidence when specifying requirements, managing risk, and engaging with surveying professionals.

A wide range of topics

TSA’s collection of Client Guides reflects the diversity of the geospatial surveying sector. From traditional ground-based methods to cutting-edge technologies, the guides cover subjects including:

• Topographical surveys
• Measured building surveys
• Setting out surveys
• Hydrographic surveys
• Aerial LiDAR
• Photogrammetry

…and many more.

If you’ve already explored our recent blog on photogrammetry, you’ll know how powerful modern surveying methods have become. The full range of TSA Guides reveals how different survey techniques work together to support everything from construction and infrastructure to environmental monitoring and asset management.

Why download a TSA Client Guide?

Reliable information can be difficult and time-consuming to sift through. TSA’s Client Guides offer a trusted shortcut, developed by geospatial experts and grounded in real-world practice.

By downloading a Guide, you can:

• Clarify your project requirements before commissioning work
• Avoid costly misunderstandings by knowing what to expect
• Understand the scope and limitations of different survey methods
• Stay aware of relevant standards and procedures
• Make better, more informed decisions

Whether you’re at the early planning stage or already working on a project, having the right information at your fingertips can make a huge difference.

Designed for easy access

All TSA Client Guides are available as downloadable PDFs, making them easy to access, share, and refer back to whenever you need them. They’re ideal for quick reading but also useful as ongoing reference documents throughout the lifecycle of a project.

If you’ve found value in learning more about photogrammetry, why stop there? There’s a whole library of guidance waiting to be explored. Each guide offers insights into a different aspect of surveying and its role in delivering successful outcomes.

Visit the TSA downloads section and discover the full range of Client Guides

Take a few minutes to browse. You may find exactly the information you didn’t realise you needed.

The Survey Association (TSA) is committed to promoting best practice and improving understanding across the surveying profession. Our Client Guides are just one way we’re helping to bridge the gap between technical expertise and practical application.

Discover TSA’s Client Guides here https://www.tsa-uk.org.uk/resources/downloads/

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Photogrammetry is one of those technologies many people rely on without realising it. If you’ve looked at a detailed aerial map, explored a 3D model of a site, or reviewed a drone survey, there’s a good chance photogrammetry was behind it.

What is photogrammetry?

At its simplest, photogrammetry is the process of using digital photographs to measure and map the real world. By taking multiple, overlapping images of the same area from different angles, specialist software can identify shared features and calculate their size, shape and position. The result is an accurate, measurable representation of the environment, ranging from 2D plans to full 3D models.

Put simply, photogrammetry turns digital photos into reliable, usable data. While the principle has been around for over a century, advances in digital cameras, drones, computer power and processing software have transformed what is possible to achieve, making photogrammetry faster, more accessible, and more cost-effective than ever.

Why is photogrammetry important?

Photogrammetry is widely used across construction and engineering, planning and design, asset management, heritage, and environmental monitoring. Its main strength is the ability to capture large amounts of data quickly and safely. In many cases, information can be collected remotely using drones or aircraft, reducing the need for surveyors to access difficult or hazardous areas.

For clients, this means faster site data capture, reduced disruption and safer workflows.

It isn’t just used for large scale areas – it can also be used to capture artefacts and objects in high detailed in controlled conditions with DSLR (Digital Single-Lens Reflex) cameras.

Does photogrammetry just produce images?

Photogrammetry produces measurable survey data that can be used throughout a project. This can include:

• Orthophotos – accurate aerial images you can measure from
• 3D meshed/textured models – ideal for visualisation and analysis
• Point clouds – dense datasets similar to laser scanning

With the correct geospatial survey practices where survey control, GCPs (Ground Control Points) and targets, are deployed – these outputs provide visual clarity and technical accuracy, helping teams make better decisions from the outset.

The resulting 3D data can be combined with 3D laser scan point cloud data and traced to produce CAD drawings, or help build 3D models in software like Revit– ready for use in design and planning.

What are the benefits of photogrammetry?

Photogrammetry offers several key advantages:

• Non-intrusive data capture (no digging or physical contact)
• Rapid collection of large datasets
• Access to areas out of visual line of sight from the ground for laser scanners
• Highly detailed, visual outputs
• A permanent digital record that can be reused over time if survey control is used

However, it’s important to recognise that results depend on good planning, high-quality imagery, and professional geospatial survey expertise. When a drone is deployed, it is important that the pilot is licenced, experienced, has gained all the relevant permissions and authorisations, and fully is insured. While the technology is more accessible, producing reliable, survey-grade data still requires experienced practitioners.

Why should you care about photogrammetry?

For clients and stakeholders, the value is straightforward. Photogrammetry gives you rich, visual data you can measure, analyse and rely on throughout your project. Used correctly, it can improve understanding, reduce risk, and support better decision-making, from early planning to final delivery.

This is just an introduction. For detailed guidance on specifications, workflows and procurement, download the full client guide from The Survey Association website.

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At TSA, we remain firmly committed to supporting our members and leading efforts to address this issue. Over the past decade, we have played a central role in driving the national response to survey equipment theft, and we are pleased to share positive progress, while recognising there is still a way to go.

Strengthening the national response

Building on almost a decade of evidence gathering with SmartWater/DeterTech, in 2025 TSA started to directly support the work of the National Construction and Agriculture Theft Team (NCATT), a specialist operational police unit established in 2023.

NCATT is unique as the UK’s only fully industry-funded specialist police unit dedicated to tackling Organised Criminal Groups (OCGs) involved in the theft of construction and agricultural equipment. Bringing together officers from across the country with expertise in rural crime and equipment theft, the team is small but highly effective.

In a relatively short time, NCATT has:

• Improved coordination between police forces nationwide
• Enhanced intelligence sharing across regions and sectors
• Delivered operational support and training
• Conducted investigations into high-value machinery theft
• Built strong partnerships with industry and European law enforcement

Importantly, NCATT has been working directly with TSA members, not only supporting individual cases of theft but also helping to unite resources across the UK to actively pursue organised crime gangs.

Real progress with a persistent challenge

There is encouraging news. NCATT and local police teams have achieved record-breaking seizures of stolen equipment, alongside arrests and significant cash recoveries across the UK. These outcomes demonstrate that coordinated, intelligence-led policing is making a real difference.

However, the national and international illicit demand for machinery remains high and continues to drive organised criminal activity, meaning that while enforcement efforts are delivering results, the risk of thefts remains.

A collaborative approach

The work of NCATT highlights the importance of a three-pronged approach:

• Prevention: strengthening security and awareness
• Enforcement: targeting and disrupting organised crime
• Collaboration: sharing intelligence and working together

By focusing on these areas, NCATT plays a critical role in safeguarding our sector, protecting vital infrastructure, and supporting the hardworking businesses that keep projects moving across the UK.

What to do if theft occurs

If you experience theft, acting quickly and following the correct process is essential to maximise the chances of recovery:

1. Report the theft immediately

Report the theft to the police force where the incident occurred. This is critical as only the relevant force can formally investigate and circulate the equipment as stolen on police systems. If your equipment has live tracking and you are not receiving a timely response, contact NCATT immediately.

2. Notify key partners

Email the equipment manufacturer and NCATT via ncatt@northumbria.police.uk to ensure NCATT is aware and can assist and the manufacturer can flag the equipment on their systems. For Leica Geosystems equipment, also notify uk.support@leica-geosystems.com

3. Provide full details

Use the subject line: “Survey Theft Notification” and include:

• Make and model
• Serial number
• Approximate value
• Date of theft
• Location of theft
• Police crime reference number

Please note that online reporting reference numbers cannot be acted upon until a formal crime number is issued by the police.

Moving forward together

While the challenge of survey equipment theft is far from over, the progress being made through collaboration with NCATT is significant and encouraging. By continuing to work together we are building a stronger, more resilient response.

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At the stakeholder event held at Twickenham as part of last month’s AGM, there was a clear and shared consensus: our profession needs greater visibility, clearer messaging, and a stronger level of public understanding.

The overarching aim of the campaign is to reposition geospatial surveying as a strategic, indispensable function across industry. We need to shift perception from viewing geospatial surveying as a technical trade, to recognising it as a professional consultancy discipline. Surveying should not be seen simply as a cost to a project, but as the strategic foundation upon which everything else is built.

A task force to drive change

Working in collaboration with O agency, we have now established a dedicated Task Force that will shape both the vision and the strategic outputs of the campaign. This group will be responsible for developing a clear 12-month plan that will form the foundation of the initial campaign strategy.

The campaign is to be built across five strategic pillars:

1. Building awareness and visibility
2. Regulations and standards
3. Industry alignment
4. Talent pipeline and education
5. Commercial value shift

To deliver meaningful change, we must influence policy and regulation, drive a shift in procurement behaviour, and build a sustainable and resilient talent pipeline for the future of the profession.

Securing the right level of funding will be critical to the campaign’s success, and the scale of its impact will depend on the level of support received from our members. Encouragingly, we are already in discussions with a number of organisations that are keen to get involved at an early stage, with strong interest and clear intent being demonstrated.

Find out more by attending the presentation by Oliver Viney at GEO Business on 3^rd June at 12:00 on the Surveying & Capture Stage. Please do get in touch if you would like to know more or get behind this campaign.

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Across the sector, more clients and client organisations are recognising its value and are actively seeking out TSA to find out more about what the scheme offers.

Why PUMA matters

Geospatial surveying is one of the essential, but often unseen, disciplines behind and under the built environment.  Raising standards in utility surveying, a specialism within geospatial surveying, has never been more important. High-quality, reliable survey data is essential to prioritise safety, improve efficiency, and ultimately save time and money on infrastructure projects.

This was the driving force behind the creation of PUMA, the PAS128 Utility Mapping Accreditation scheme and feeds directly into the national marketing campaign recently launched by TSA

Developed over ten years by TSA, PUMA represents a significant step forward for our profession. It provides a robust and independent way to assess whether geospatial surveyors can consistently deliver work in line with the PAS128 specification.

Building confidence through accreditation

For accredited TSA members, PUMA offers a clear and credible way to demonstrate compliance with PAS128:2022. Crucially, it also gives clients confidence in both the level of service and the accuracy of the data they receive.

Every PUMA-accredited company has undergone independent audit, ensuring that:

• Survey outputs meet PAS128 requirements
• Working practices are robust and consistent
• Staff are properly trained and demonstrably competent

This means that when clients choose a PUMA-accredited company, they can be assured they are working with a provider fully equipped to deliver reliable, compliant survey data.

Raising the bar for utility surveys

By standardising how PAS128 surveys are delivered, PUMA has raised the bar for the entire construction industry. It establishes a benchmark for quality, giving accredited companies a powerful way to differentiate themselves and prove their capability.

Equally, it simplifies decision-making for clients, who no longer need to rely solely on claims of compliance as they have independent assurance.

PUMA is administered by LRQA, a global leader in assurance, certification, and inspection services, further strengthening the scheme’s credibility and rigour.

A scheme gaining real traction

What’s particularly encouraging is how quickly PUMA is gaining recognition across the sector.

With a number of major infrastructure projects in the pipeline that will require PAS128 surveys, we are seeing a shift in client expectations. Organisations with large contracts are beginning to explicitly request that PUMA accreditation is written into project requirements.

In many cases, they are actively reaching out to TSA to better understand how the accreditation works and how it can support their project delivery.

PUMA is increasingly being recognised as the gold standard for PAS128 surveys.

Looking ahead

The momentum behind PUMA signals a positive change for the industry. For survey companies, this is an opportunity to demonstrate excellence and stand out in a competitive market.

For clients, it is a chance to reduce risk, avoid costly delays, and ensure confidence in the data that underpins their projects.

Find out more about PUMA

If you’re interested in learning more about PUMA accreditation and how it could benefit your organisation or projects, we encourage you to get in touch with TSA.

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Preserving our past

3D Geospatial Surveys are the ultimate way of recording and keeping track of the condition and change in old buildings. These types of specialist surveys, guided by Historic England’s specification, will capture buildings, important sites, structures and even landscapes in high detail and accuracy. It is useful data for government, councils, conservation specialists, estates, and private owners to evaluate and maintain their assets, providing a snapshot for present and future guardianship.

The 3Ddata, drawings, and models are then used to inform planning or conservation decisions, to ensure that any intervention balances the need for modernisation or retrofit with conservation and preserving the historic fabric. In this way, we can both preserve the past and ensure a future for these buildings and monuments, with the emphasis on their importance and place in our cultural landscape.

Protecting the future

A heritage geospatial survey provides accurate, reliable measured data to support the understanding, conservation, repair and long-term management of historic buildings, structures and landscapes. A specialist geospatial surveyor will be guided by Historic England’s Geospatial Survey Specifications for Cultural Heritage (2024), selecting appropriate methods according to the significance, complexity and intended use of the site or asset.

This may include desk-based preparation, review of existing information, site assessment, survey control, terrestrial laser scanning, mobile mapping, photogrammetry, GNSS, UAV survey, topographical survey and measured building survey techniques. The objective is not simply to produce a “normal as-built survey”, but to create accurate, appropriate and well-structured geospatial data that records the form, position, geometry and spatial relationships of the heritage asset.

Depending on the project requirements, this data may document architectural features, such as windows, staircases, doorways, arches, roof structures, floor levels, wall alignments, decorative elements, and areas of deformation or movement. It can also support condition surveys, conservation planning, structural assessment, archaeological interpretation, retrofit design, maintenance strategies, and future monitoring.

Heritage geospatial surveys are therefore an essential part of responsible conservation practice. They help ensure that decisions about repair, adaptation, development, renovation or retrofit are based on accurate information, reducing the risk of avoidable damage to historic fabric and helping protect irreplaceable cultural heritage for the future.

Building trust and confidence

TSA Council Member Andy Beardsley MRICS, a chartered geospatial surveyor and Managing Director of Terra Measurement, has spoken extensively about the importance of Heritage Surveys and their place in the surveying landscape.

“For over 30 years, I’ve worked in geospatial survey measurement and monitoring, much of that on historic structures. And what concerns me today is not technology or software, it’s decision-making. Because the risk to heritage today is no longer a lack of care, it’s false confidence in inadequate information. Information that looks complete because it’s detailed, because it’s visual, because it’s been modelled, but it hasn’t been fully verified. So, decisions get made, designs progress, procurement follows, and the risk is already embedded. ‘It looks detailed’ is not the same as being right.

“Every time we measure an historic building, we are making a decision about how well it will be understood, not just today, but in the future. There is a campaign by The Survey Association that has just begun and it puts this theme more bluntly. If geospatial surveyors stop tomorrow, the cracks begin to show. But this is a metaphor. It’s not just about physical cracks. It’s cracks in coordination, in communication, in confidence and in the financial stability of construction projects. Because when the information isn’t reliable, teams stop trusting it – and when teams stop trusting the information, they start to make their own decisions on site, under pressure, without a shared reference point or survey. And that’s where risk multiplies.” 

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Running a survey business can be an enjoyable challenge but it can also be very stressful for many reasons. Combined with tight budgets, economic uncertainty, staff shortages and the pressure to deliver precise results, stress can quickly build.

For those in smaller teams, or surveyors working alone, there may be fewer opportunities to share concerns or decompress with colleagues. And although surveying is a diverse profession, many individuals may not feel naturally inclined to open up or ask for support, even when it’s needed.

Be proactive with protecting your mental health

That’s why it’s important to be proactive. Looking after your mental health doesn’t require dramatic change, as small, manageable actions can have a significant impact. On site, this might include:

• Taking regular breaks, even short ones, to reset and avoid fatigue
• Staying connected, checking in with a colleague or friend during the day, for more than just health and safety reasons
• Planning your workload realistically wherever you can to reduce unnecessary pressure
• Getting fresh air and movement, beyond the task at hand, to clear your mind
• Recognising early signs of stress, like irritability or difficulty concentrating, and addressing them early.

Team leaders can support this proactivity by creating open cultures where wellbeing can be discussed freely. Ultimately, taking care of your mental health is not a luxury, it’s essential. You don’t have to handle everything alone. This May, let’s encourage everyone in the surveying community to look after themselves and each other.

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Depth of knowledge

The answer, of course, is “All at sea”. Hydrographic surveys are an important aspect of global mapping and are useful at finding a myriad of features and structures concealed by water. In the same way that underground utility surveys reveal what lies beneath ground level, hydrographic surveys explore the depths of various bodies of water. They are a practical way to explore oceans, the sea, inlets, harbours and coastal areas, lakes, rivers, meres, pools, estuaries and other watery expanses.

Hydrographic surveys map areas such as ocean floors and riverbeds, to show how the ground undulates and indicates depths and other data. They can be used for civil engineering projects, such as bridges, or for maritime projects like dredging or environmental issues. They can also map the ocean floor for navigational purposes.

Expansive projects

River and canal surveys have defined parameters and follow the course of the waterways, whereas oceans and seas are more complicated and expansive, requiring survey vessels and other equipment. But they don’t just explore and map subaquatic landscapes. They are also used by maritime industries, construction firms, insurance companies and government agencies to inspect, map and evaluate submerged structures and vessels. They are essential for ensuring the safety and maintenance of bridges, harbours and waterways, docks, oil rigs and pipelines, as well as checking the condition of boat hulls and the position of wrecks.

The importance of geospatial surveyors is exemplified by the number of sectors the profession can be involved with – everyone from environmental campaigners, cartographers and construction projects, to local councils, planners and lawyers settling boundary disputes. Hydrographic surveys are another discipline and a specialist area of surveying knowledge, with its own equipment and skillsets. Once collected, the digital data can be processed to create digital models and 3D views of the terrain or structure. This information is invaluable, as so much beneath the waterline is unseen and unknown.

Dive into a new career in geospatial surveying

The breadth of knowledge required to be a surveyor goes beyond maths and an ambition to work outdoors. There are many different disciplines that feed into surveying and people with all kinds of backgrounds enter the profession. The flexibility and appeal of working outside and inside – not simply being office-based – is a big draw for many people. It’s also a career that can be learned and enhanced whilst doing the job. This can be via apprenticeships, with professional qualifications available and ongoing development an option, through courses such as The Survey School curriculum and other organisations and bodies.   

There’s a lot more information about routes into surveying here https://www.becomeasurveyor.com/ with case studies and practical insight into how to join the profession and map out a successful career.

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