Introduction

In the quickly developing field of aerial surveying, Drone Photogrammetry, which combines measurement science with the state-of-the-art capabilities of Unmanned Aerial Vehicles (UAVs), is a game-changer. From the fundamental ideas behind drone photogrammetry to its wide range of applications, this in-depth guide explores all the practical aspects. Whether you're a seasoned professional or a curious newcomer, this comprehensive guide will help you understand the advantages and disadvantages, explore practical applications, and master the unique terminology of drone photogrammetry.

We'll talk about the deliverables, contrast PPK and RTK positioning systems, and compare LiDAR and photogrammetry. We'll also examine the best software choices for photogrammetry drafting. In addition, we'll look ahead at drone photogrammetry and negotiate the complicated terrain of laws and regulations. Come along on this journey to see how technology is changing data collection and providing fresh viewpoints across various sectors. Here is your comprehensive guide to Drone Photogrammetry.

What is Drone Photogrammetry?

Photogrammetry is the process of converting aerial images taken from different angles into 3D models or maps. This helps to get a better understanding of the depth, measurements, and size of the land or object that has been captured. Also, the industry has been growing in different areas of life. Now, data collection in photogrammetry is performed through various devices, but the drone is one such technology growing at a fast pace. Let us now take a look at what Drone Photogrammetry looks like and why it is growing all over the world.

Drone Photogrammetry is a way in which the aerial images taken from drones are collected and processed to make 3D models and maps using specialized software. These drones are Unmanned Aerial Vehicles (UAVs) that help to get images of the earth’s surface from different viewpoints. These images are processed using special software to get various spatial data, apart from 3D models and maps. The photographs taken from the UAVs are overlapping photos taken from different angles and heights.

In recent years drone photogrammetry has been used in different sectors like agriculture, land surveying, construction, environmental monitoring, and more. This helps people understand the land and its condition in a better way to make the best use of it. Also, this helps to generate highly detailed and accurate maps and models of the area.

Being in such high demand, the new technology has its advantages and disadvantages. Let us look at some of those in detail.

Benefits and Drawbacks of Drone Photogrammetry

• Cost & Time Effective

Drones cost less than traditional aerial survey methods. The aerial survey is conducted using manned aircraft, which makes the cost high. As a result, aerial surveys were primarily accessible only to big-scale companies. But, with the coming of drones, small-scale companies can afford this too.

Also, drones allow coverage of larger areas in a short amount of time. This saves a lot of time and allows quicker delivery of the results. This cost and time-saving aspect play an essential role in large-scale projects.

• Environmentally safe

The lesser emissions of fuel and carbon footprints make drone surveying environmentally friendly. With the increasing effects of global warming, this proves to be a better option for the surveyors. Also, it has minimal ground disturbance as compared to traditional methods.

• Easy to operate

Drones are easier to operate and do not require complete manhandling. It can be monitored and controlled remotely by sitting in one place. Allows access to different and difficult terrains that need monitoring.

• Safe to operate

Drones are easier to operate than manned aircraft or traditional surveying tools. Operating drones allows access to areas difficult to reach through aircraft, like high-volcano-prone areas, difficult terrains, dense areas, war areas, and more. It helps to capture data from various angles and heights, allowing better results for data processing.

• High-quality Data

Drones with high-quality cameras provide high-resolution images that help improve the quality of maps, models, and other spatial results. Also, drones can fly at a lower altitude than manned aircraft or satellites, providing clearer images of the area to be monitored. This allows for better results in the data.

• Real-time Data Monitoring

Some of the drones allow real-time data monitoring, which helps collect data at the moment and monitor the area for real-time progress and the condition of the projects. This real-time data monitoring helps in making on-the-spot decisions when and where required. Also, this functionality is useful in instances where quick action is required or for time-sensitive applications.

Drawbacks of Drone Photogrammetry

• Limited performance in difficult weather conditions

Special weather conditions like rain, fog, storms, or low-light conditions can affect the collection of data through drones. Also, areas with dense vegetation, overgrown terrains, and complex areas with dense cable connections are difficult to monitor using photogrammetry.

• Limited flight time

Drones come with a limited battery life and performance time. This reduces the area limit to cover a single charge/flight. Also, it will require multiple flights to cover a larger area to survey. The battery typically lasts for around 25-30 minutes, which limits the area covered by a single charge.

• Limitations to Ground Sample Distancing (GSD)

Ground Sample Distance (GSD) is affected due to the sensor size, aperture, resolution, focal length, and flight attitude. These things in a drone need to be carefully planned and adjusted to get the best results. Also, this can affect the final results of data processing.

• Complex Data Processing needs

The data collected using drones requires specialized software and experts at the end. This makes the process more complex and time-consuming. Also, generating 3D models and maps may create challenges for some users.

• Possibility of device malfunction

Drones might face technical failures or malfunctions that can lead to data loss or delay in data collection. These failures can be a loss of GPS signal, a motor failure, or other technical glitches. This can even lead to accidents when the drone fails.

• Adherence to Regulations

Obtaining the necessary permits and complying with regulations from civil aviation authorities can sometimes lead to complexity and delays in projects. These permits are important for the smooth operation of the drones without further interruption from the authorities.

Terminologies in Drone Photogrammetry

While learning about Drone Photogrammetry, one can come across new terminologies. These terminologies are very simple to understand. Let us discuss some common terms you can come across often.

• Ortho Photos/Images

An orthophoto is an aerial image that has been flattened, geometrically adjusted, and has a consistent size and perspective. It is perfect for accurate measurements in photogrammetry. Adjustments for lens distortion and camera tilt ensure an accurate representation of the Earth's surface.

• Orthomosaic Map

An ortho-mosaic map is a photograph of a region that is high-resolution, distortion-free, and created by stitching together overlapping drone photos. It ensures a constant scale after correcting for aberrations, making accurate measurements of areas and distances possible. This georeferenced map is essential for urban planning and land surveying applications.

• Remote Sensing

Remote sensing utilizes sensors and aerial photography to create detailed maps for measurement and analysis. To collect data about a region without making physical contact—such as UV and infrared radiation—photogrammetry, a crucial instrument in remote sensing, analyzes photos from sensors installed on unmanned aerial vehicles (UAVs), manned aircraft, and satellites.

• Geographic Information System (GIS)

Geographic Information Systems (GIS) combines satellite location data with high-resolution images for mapping applications. Google Earth is a well-known GIS tool for meteorology, surveying, navigation, and other uses. These systems gather, store, process, and display geographic data; they frequently work with photogrammetry to create maps and three-dimensional models.

• Metadata

Photogrammetry metadata, such as GPS coordinates, time/date stamps, camera settings, and more, offers critical contextual information for orthoimages used in mapping and modeling tools. The consistency of size and viewpoint established by this data's availability improves the dataset's quality and usability.

• Ground Sampling Distance (GSD)

In drone-captured photography, Ground Sampling Distance (GSD) is the distance between two successive pixel centers on the ground, usually expressed in meters per pixel. It is closely related to the image's spatial resolution, affecting its capacity to capture minute details. Greater picture resolution, which provides more precise information for photogrammetry processing, is indicated by lower GSD values.

• 3D Point Cloud

Using overlapping photos taken during drone operations, a 3D point cloud offers a precise depiction of surface geometry. With millions of XYZ coordinate points, it is used for a variety of tasks such as landscape analysis and 3D model creation, providing a thorough overview of the surveyed region.

• Digital Elevation Model (DEM)

The Digital Elevation Model (DEM) is a three-dimensional depiction of the Earth's surface that displays topographical characteristics and elevation changes. DEMs, derived from point cloud and drone photos, are crucial for infrastructure management, environmental evaluation, and urban planning.

• Digital Terrain Model (DTM)

After above-ground features are eliminated from a Digital Surface Model (DSM), a 3D depiction of the uncovered Earth is created, known as a Digital Terrain Model (DTM). With their ability to provide information on terrain elevation for analysis, DTMs are essential for hydrological modeling and land-use planning.

• Georeferencing

Georeferencing verifies accuracy in drone photogrammetry by comparing images or three-dimensional data with actual places. To make sure that ortho mosaics, point clouds, and 3D models accurately depict real locations, it correlates spatial coordinates with photos using GPS data or ground control points.

• Ground Control Point (GCP)

When georeferencing and aligning aerial photos for photogrammetry projects, a Ground Control Point (GCP) is a designated location on Earth's surface with known coordinates. To enable precise placement in photogrammetric processing, the exact coordinates of GCPs—visible on the scanned item or area—are measured.

After getting a brief knowledge on what is drone photogrammetry and some of its basic terminologies, let us now understand its process in detail.

Working Process of Drone Photogrammetry

While conducting Drone Photogrammetry there are certain steps that one needs to follow. But before getting to know the flow of conducting Drone Photogrammetry, there are things that one needs to keep in mind. Let us see what are these important things to be kept in mind.

Things to Keep in Mind

1. Accuracy - The top priority

Before capturing images, or marking a particular object, getting accurate Ground Control Points (GCPs) is very important. They enhance the accuracy of the photographs taken. They are known as physical markers with coordinates for the precise outputs. Also, to have accurate images and production, make sure to set the camera to save geo-location.

2. Precise Camera Settings

Keep the camera settings manual, as the automatic exposure settings can provide inconsistent results. Adjusting the settings manually can maintain a consistent flow of image quality.

3. Number of Images captured

Taking an ample amount of images for overlapping will ensure accuracy while stitching and mapping. While having images, take more side laps as they give more precise alignments.

4. Use of advanced techniques

The use of advanced techniques provides more accurate results. Use advanced surveying tools like Total Stations, GPS technologies, or laser scanners. Also, incorporating analytics engines for data analysis and interpretation can help.

5. Getting an optimized workflow

To get the best results, collect accurate GPS coordinates using GCPs. Along with this manual mode for camera settings like aperture, ISO, and shutter speed. A consistent flight altitude and speed are important, to have a uniform ground resolution. Verify the weather before takeoff to prevent negative impacts on drone stability and picture quality. You should also do quality checks on photogrammetry outputs to correct any problems.

6. Optimal Procedures for Flight Planning

Adjust flight parameters according to project and equipment specifications, ensure sufficient image overlap for accurate 3D modeling and orthomosaic creation, use GCPs for precise photogrammetry results, comply with drone regulations, and conduct pre-flight checks for safety.

By following these guidelines and best practices, drone photogrammetry practitioners may maximize workflow accuracy and efficiency, producing dependable insights and high-quality data outputs for different applications.

Now, let us jump to the steps to follow while conducting Drone Photogrammetry.

a) Initial Site Evaluation

Before beginning the photogrammetry process, evaluation of the area being surveyed is important. Understanding the topography with potential obstacles will help set clear goals for the survey.

b) Selecting the Appropriate Equipment

According to the project’s size, resolutions, and environmental conditions, select the drone and camera. Also, consider factors like flight time, camera resolution, and payload capacity.

c) Planning the flight path

Flight paths can be planned using drone mapping software that allows enough overlapping between images. To cover the entire survey area systematically, this planning is important.

d) Ground Control Points (GCPs)

GCPs are visible markers on the survey area that are used for the alignment of captured data. This helps to enhance the accuracy of the final model.

e) Carrying Out the Flight

Now, with all the settings, the flight can be carried out. Fly it on the pre-defined path with a steady speed and altitude. According to the battery life, keep the drone in sight and adjust it whenever necessary.

f) Data Processing

After capturing the images, use the photogrammetry software to stitch them together. This will give you a 3D model of the survey area. Now, after the data is collected certain processes are carried out before the final delivery of the results. They are as follows -

Data Collection: Fly the drone to capture aerial imagery or other data using its onboard sensors (such as cameras, LiDAR, etc.) and GPS.

Data Transfer: Transfer the collected data from the drone's storage to a computer or processing device.

Pre-processing:

Data Cleaning: Remove any corrupted or unusable data points.

Georeferencing: Align the data collected with real-world coordinates using GPS information.

Image Processing: If working with images, perform tasks such as color correction, stitching (for multiple images), and resolution adjustment.

Data Processing

Point Cloud Generation: Convert the collected data into a point cloud format, representing the surface of objects in 3D space.

Mesh Generation: Create a mesh model from the point cloud, providing a more detailed representation of surfaces.

Texture Mapping: Apply textures from images to the mesh for visual realism.

Analysis and Interpretation

Feature Extraction - Identify and extract specific features from the processed data, such as buildings, roads, vegetation, etc.

Measurement and Analysis - Take measurements and perform analysis tasks based on the processed data, such as volume calculations, distance measurements, etc.

• Output Generation

• Orthomosaic: Create an orthomosaic, a high-resolution, georeferenced aerial image made by stitching together multiple images.

• Digital Elevation Model (DEM): Generate a DEM representing the elevation of the terrain.

• 3D Models: Produce 3D models of the surveyed area based on the processed data.

• Reports and Visualizations - Generate reports, maps, and visualizations based on the analysis and interpretation results.

• Quality Check - Perform a quality check to ensure that the processed data and outputs meet accuracy and quality standards.

• Data Presentation and Delivery - Present the processed data and outputs to stakeholders or clients in the desired format (e.g., reports, maps, interactive visualizations).

7. Evaluate and Improve

After the model is created, check for inconsistencies or gaps in the data. If more data has to be collected, go back to the site and use software tools to refine the model.

8. Final Delivery

The final product for the client can be delivered in different formats like Digital Maps, 3D Printed Models, or other visual representations.

Thorough planning is essential for photogrammetry projects to be successful because it guarantees high-quality picture processing and capture for accurate 3D models. A bright future for various businesses is promised by drone photogrammetry, which provides economical, effective data collecting with integration possibilities for cutting-edge technologies like AI and AR. After discussing how we can perform drone photogrammetry, let us look at some of the top Drone models we can use.

Best Drones for photogrammetry from basic to advanced

There are a lot of drones in the market that can conduct photogrammetry. But, only some can give you the best results. Take a look at the selected drone models that we think best fit the photogrammetry process.

1. DJI Matrice 300 RTK + P1 Sensor

DJI Matrice 300 RTK + P1 Sensor is a high-end drone designed especially for commercial use. It comes with advanced features for better performance in difficult conditions. It can cover large areas giving high accuracy. Also, it is compatible with the Zenmuse P1 sensor to give precise photogrammetry results.

But, being this good in the market, comes with pros and cons and they are -

Pros

a) A total of 55-min battery life

b) Good RTK positioning

c) Sturdy and portable design

d) Several different payload options

Cons

a) Costly

b) Compact controller display

2. WingtraOne Gen II

The WingtraOne Gen II is specifically designed for surveying and mapping use. It comes with a wide-angle camera feature to get detailed imagery. Also, it can be easily maintained with a high-resolution camera and low GSD for correct mapping.

Its pros and cons include -

Pros

a) Enhanced features for dependability

b) Changeable cams

c) Prepared for remote ID

d) Accurate landing with precision

Cons

a) Decreased redundant work

b) No more than five payloads

3. DJI Phantom 4 RTK

DJI Phantom 4 RTK comes with specific RTK positioning that gives accurate aerial mapping. It can be easily used by beginners with intelligent software features. Also, it has a 20 MP camera with a 1-inch sensor for high-quality imaging. This can also cover large areas and give a stable performance.

Pros

a) Reasonably priced

b) Accurate imaging

c) Easy enough for beginners

d) RTK comprised

Cons

a) Comparatively short battery life

b) Set payload

4. SenseFly eBee X

Fixed-wing flight capabilities and wider coverage are provided by the SenseFly eBee X Drone. Its replaceable payloads allow it to be adaptable, and its lightweight design complies with regulations. It can fly accurately for up to ninety minutes.

Pros

a) Lightweight

b) Extended battery life

c) Very precise

d) Numerous swappable payload options

Cons

a) More challenging to use

b) Separate sales are made for ground stations.

5. Censys Sentaero BVLOS

With its versatile payload system that works with many photogrammetry choices, Censys Sentaero BVLOS is designed for long-range, beyond-visual line-of-sight (BVLOS) missions. Its detect-and-avoid technology, which ensures safety and dependability in aerial operations, allows for real-time danger identification during flights.

Pros

a) Able to function in challenging environments

b) Identify and prevent system

c) Focused on BVLOS

d) A lot of redundancy

Cons

a) Costlier

b) Difficult to transport or carry

These were the top 5 drones that we have picked from our research. But, depending on the use and budget, you may find some other drones in the market useful. The choice can completely rely on the drones that you want to use for what purpose.

Costing of Drone Photogrammetry

The cost of a photogrammetry drone varies based on several aspects, including model, manufacturer, accessories, and specs. Drones with entry-level characteristics for small-scale projects usually cost between $500 and $2000, and they don't have PPK or RTK. Better cameras and obstacle avoidance are features of mid-range drones, which run from $2000 to $5000 and are appropriate for medium-sized tasks. Professional-grade drones, which may cost anywhere from $5000 to $20,000 or more and are perfect for intricate and large-scale projects, come with high-resolution cameras and sophisticated systems like PPK or RTK. It's also important to factor in additional costs for peripherals like batteries, cameras, and software licensing. In conclusion, the cost of a high-end photogrammetry system, including peripherals, usually ranges from $4000 to $13,000.

LiDAR vs Photogrammetry: Which is better for Data Collection

There are two ways to collect data to perform the Drone Photogrammetry process. Let us understand both and know which is better for data collection.

What is LiDAR?

LiDAR is an abbreviation for Light Detection and Ranging. This is a remote-sensing technology that measures distance using laser pulses. It emits precise laser pulses to the target area, calculates the time required for the laser to return, and then generates a dense point cloud to represent the object or terrain. LiDAR is used to create accurate 3D representations of terrains and objects. This technique can be used in forestry management, environmental studies, geological surveys, urban planning, and more.

What is Photogrammetry?

Photogrammetry uses overlapping images captured using drones or manned aircraft to generate 3D models or maps. In this, the photogrammetry software processes overlapping images that identify shared points and create a 3D model. It is used in archaeological site documentation, environmental studies, construction monitoring, and more.

Now that we know the meaning and workings of LiDAR and Photogrammetry, let us see the pros and cons of each.

Pros and Cons of LiDAR Pros

a) Unmatched precision, down to the centimeter.

b) It can pierce vegetation, making it appropriate for mapping in heavily wooded regions.

c) Functions with dependability in dim or no light.

d) Gives comprehensive 3D models and accurate elevation data.

Cons

a) More costly than photogrammetry.

b) Sophisticated software needs and data processing.

c) Limited capacity to record texture properties and RGB colors.

d) Narrower range than photogrammetry and depends on line-of-sight.

Pros and Cons of Photogrammetry:

Pros

a) More affordable than LiDAR.

b) Produces detailed, aesthetically pleasing 3D models from high-resolution photos.

c) Adaptable and suitable for a range of application cases and industries.

d) Comparatively easy data processing with contemporary software.

Cons

a) Restricted penetration in regions with tough terrain or thick vegetation.

b) It depends on having adequate illumination to take decent photos.

c) Prone to phenomena like bloom and lens distortion.

d) Difficult to navigate in dim or obscured situations.

After understanding the pros and cons of each, there still needs to be clarity in choosing which is better. To understand which one to choose, you can refer to our article on LiDAR vs Photogrammetry.

Deliverables from Drone Photogrammetry

Some of the common outputs one can receive from Drone Photogrammetry are as follows:

Ortho mosaics:

Ortho mosaics are detailed and accurate maps of an area, made by stitching multiple photos captured using a drone. These are also known as georeferenced aerial images. The scale of these images is corrected and made uniform.

3D Point Cloud:

3D Point Cloud is a collection of 3D points representing the shapes of different objects or landscapes on the ground using many tiny dots and recreating the miniature of the world around us.

Mesh Models:

3D Mesh Models are interconnected polygons made using point cloud data. They represent the surface topology in 3D along the X, Y, and Z axis. These are made using the overlapping images collected through drones.

Contour Maps:

These are maps made out of lines connecting dots of equal elevation to get a detailed 3D visual of the terrain and the landscape. Slope analysis, landform categorization, and landscape visualization depend on contour maps.

Digital Surface Models:

Digital Surface Models (DSMs) are aerial photographs that contain both, natural and artificial, structure height data. Every elevation has its height marked as a cell or pixel, with the height calculated as the difference between sea level and that point.

2D/3D Models:

2D maps or 3D models, are the representation of the geographical area using drone-captured images. Maps provide an image look of the Earth’s surface, while 3D models give you the depth of the images captured.

Real-life applications of Drone Photogrammetry

Many industries require photogrammetry as a service where they collect and analyze the data. However, many require an aerial vision of the area and a deeper understanding. Here comes the use of Drone Photogrammetry.

Oil & Gas:

In the oil & gas industry, remote checking and inspection of pipelines and infrastructure are carried out using drones. This is also used to keep the remote infrastructure secure. With the increasing integration of AI in every industry, it is also used in photogrammetry to detect leaks and issues in pipelines for faster solutions. This helps in the protection against any large damage or future disaster.

Construction & Infrastructure

In construction, drone photogrammetry helps in site planning, asset inspection, condition tracking of the project, examining terrain features, identifying issues in development, and more. This helps keep track of the work and ensure that the timeline is met. These drones, equipped with sensors and AI, help to inspect bridges, roads, and buildings, which helps to detect damage and structural issues.

Agriculture:

Drones help companies holding large areas of land for agriculture keep an eye on the ground from a bird ' s-eye view. This helps to detect crop growth, yield estimation, soil erosion issues, crop diseases, and more. Also, this gives them real-time information on drainage, pest infestations, low-fertile areas, drought stress in the region, timely reminders of harvesting, irrigation, and more. Thus enhancing crop management and increasing agricultural productivity.

Mining and Quarries:

Drone photogrammetry helps to create detailed terrain models, 3D maps, and DTMs to get a detailed vision of the mining site. This helps in surveying, inventory management, identification of potential hazards, stockpile estimation, tracking changes, volume calculations, planning extractions, and more. Also, it allows us to evaluate process efficiency and environmental compliance.

Environmental Monitoring:

Environmentalists are using drones to monitor land changes, pest infestations, wildfires, deforestation tracking, erosion mapping, flood detections, and habitat tracking. This helps in making rescue strategies, mitigating risks, monitoring sensitive changes, and a way of sustainable natural resource management. Drones being cost-effective and leaving fewer carbon footprints help to gain more detailed information.

Telecommunication:

Drones enhance safety and efficiency while facing power issues or during telecom repair operations. This helps workers and engineers prepare detailed repair plans beforehand to minimize surprises during tower inspections. Also, the solar-equipped drones help to solve connectivity and internet issues in disaster-stricken rural areas for a temporary period.

Best software for Drone Photogrammetry

There are many drone photogrammetry software to use, but here are the top picks to be used for the best results.

Pix4D:

Pix4D is well known for its advanced technology that can transform images taken from various sources like drones, planes, phones, or other cameras. Its flagship product, Pix4DMapper, has automatic tie point detection, georeferencing, and customizable processing settings. It allows for cloud-based processing to handle large datasets. Pix4DMapper is also recognized as an industry leader as it excels in producing accurate 3D models, point clouds, orthomosaics, and DSMs. It is also compatible with common industry tools and professional mapping applications. To excel in photogrammetry, Pix4D and Pix4DMapper are a valuable ally, enabling precise scaling of imagery projects.

DroneDeploy:

DroneDeploy, another photogrammetry and mapping application, is a cloud-based drone mapping software. It offers automated features to stitch images, 3D model generation, and precise measurements. The software is accessible and efficient for new learners and experts. Also, it is compatible with a wide range of drones, with utilization in more than 120 countries, and a user-friendly mobile app. It is considered to be one of the top applications in the construction and agriculture industries. The application is trusted by users worldwide, empowering businesses with reality-capture capabilities. It also can provide a seamless platform for integrating aerial and ground data. Its AI-powered analysis and automated reality capture make it more usable for companies.

OpenDroneMap:

Another software that we have is OpenDroneMap, an open-source software that makes it accessible and cost-free. The software can generate orthomosaics, point clouds, 3D models, and other outputs from aerial imagery. The software is well-known worldwide and can be seen used in the American Red Cross’s portable OpenStreetMap system. This software gives out accurate maps and models, and fosters collaboration within the field with different communities.

These were the three top software or applications one can choose for the best photogrammetry results. There are several other software and applications too in the market that you can check for better results.

Along with these, many companies or organizations provide Drone Photogrammetry Data processing services. Gsource stands at the top to provide this data processing service. Gsource leads the way in providing Drone Photogrammetry Data processing services, offering precise data modeling, innovative digital twin development, and comprehensive federated model creation. Whether your requirements are in building engineering and construction, land use and planning, or product information modeling, Gsource is ready to fulfill them.

PPK vs RTK: Positioning in Drone Photogrammetry

In drone photogrammetry, precise positioning is essential to producing high-quality and accurate orthomosaics. To get this degree of precision, Post-Processed Kinematic (PPK) and Real-Time Kinematic (RTK) are two of the most used methods. We'll go over each of these methods in-depth in this part, along with how they may greatly increase the precision of your drone photogrammetry missions.

• What is PPK?

For accurate positioning in drone photogrammetry, PPK (Post-Processed Kinematic) is utilized. PPK involves recording raw GNSS (Global Navigation Satellite System) data during flight, which is later processed in conjunction with data from a fixed base station to correct the drone's location. The geolocation precision of this post-processing technique is centimeter-level.

• What is RTK?

In drone photogrammetry, RTK (Real-Time Kinematic) is another exact positioning method. With RTK, the drone receives real-time correction data during flight from a base station, allowing for immediate centimeter-level localization accuracy.

Now, to choose between PPK or RTK, we need to understand the benefits and drawbacks of both.

Benefits and Drawbacks of PPK:

• Benefits:

High precision - Orthomosaics and 3D models are produced with greater quality because of PPK's centimeter-level accuracy.

Flexibility- GNSS data may be reviewed and modified after processing, which could improve the outcomes.

Reduced needs for real-time data transfer between the drone and base station - PPK processing takes place after the fact, obviating the necessity for post-mission data transmission.

• Drawbacks:

Learning Curve - PPK processing can be complex for beginners to understand and may call for certain knowledge and abilities.

Less Real-Time - PPK requires post-flight data processing, which causes the availability of accurate geolocation data to be delayed.

Cost of Equipment - The additional hardware needed for PPK drives up the total cost of a drone photogrammetry system.

Benefits and Drawbacks of RTK:

Benefits:

Accuracy in real time: During the flight, RTK provides centimeter-level precision, allowing for quick evaluation of geolocation data.

Quicker processing: Post-processing is not necessary when using real-time adjustments, which accelerates the production of photogrammetry outputs.

Drawbacks:

Communication requirement: RTK relies on a constant data link between the drone and base station, which might be affected by interference or the terrain.

Possibility of real-time errors: erroneous base station data or communication disruptions might result in erroneous real-time adjustments.

After knowing the benefits and drawbacks of PPK and RTK, there are certain factors we need to look into. Let us look into them.

Which is the better option to select?

The decision between PPK and RTK is based on the preferences and requirements of the project -

• Projects where post: Processing is acceptable and more accuracy is desired should use PPK.

• For projects with a tight deadline and the need for real-time accuracy input while in flight, RTK is the better option.

In the end, choosing the best approach requires balancing variables including project requirements, equipment compatibility, financial constraints, and data processing capabilities.

Understanding Image Overlapping

Image overlap is important for getting accurate 3D models in drone photogrammetry. Image overlap, through frontal and side overlaps, helps in feature matching, enabling the creation of accurate orthomosaics and 3D models. Around 70-90% of image overlap is recommended for better results. In dense vegetation, higher image overlap is required. Thus, proper image overlap ensures accurate photogrammetry results.

Drone photogrammetry overlaps mostly into two categories

Frontal Overlap: Sometimes called Forward Overlap, is the space that is shared by two successive images that were captured along the drone's route.

Sidelap: This is the space between two images that were shot parallel to one another.

Factors influencing the required amount of overlap -

Terrain: Areas with a lot of elevation change, such as mountains, may require more overlap. Flat terrain may require less.

Vegetation: The program finds it more difficult to match up images when there are a lot of plants. You may need to overlap more in some areas.

Altitude of Flight: The drone can see more up high, thus you may require less overlap. However, greater overlap may be required if you're further down and want detailed images.

Camera Zoom: More overlap may be required since some cameras have a narrower field of view. You may require less since others perceive more.

What You Want: You may want more overlap if you require intricate maps or images. You may require less overlap if you can live with less detail.

This was about image overlapping and why it plays an important role in Drone Photogrammetry.

Regulations and Legal Considerations for Drone Photogrammetry

To conduct Drone Photogrammetry, there are several regulations and legal considerations that need to be kept in mind. This is to ensure safety, legality, and compliance. The regulations and legal considerations are -

• Licensing and certifications: Verify that commercial drone activities comply with any local licensing or certification regulations.

• Drone registration - To ensure responsibility and traceability in the event of an incident, register your drone with the relevant aviation authorities.

• Vision line of sight - Keep the drone in the pilot's direct line of sight to maintain situational awareness.

• Restrictions on airspace - Comply with airspace laws, particularly when they are close to airports or other critical locations.

• Maximum altitude restrictions - Remain below the indicated upper bounds, which are normally 400 feet (120 meters) above sea level.

• Regulations regarding privacy - When flying over private property, get permission and abide by the law.

• Obtain the required authorizations or exemptions for certain activities, such as flying in regulated airspace.

• Insurance coverage - To reduce the danger of mishaps or property damage, think about getting drone insurance.

• Stay Informed: Continuously update your knowledge of local drone regulations and certification requirements to ensure safety and compliance.

• Retain professionalism: To gain the respect and confidence of your clients, show that you are dedicated to safety and compliance.

Drone operators can perform photogrammetry operations in a safe, lawful, and responsible manner, reducing risks and guaranteeing the success of their projects, by abiding by these rules and legal concerns.

Future of Drone Photogrammetry

Drone photogrammetry is expected to increase significantly in the future due to rising applications across several sectors, technical improvements, and growth prospects. Here's a detailed rundown -

• Market expansion

Photogrammetry services are fueling the explosive expansion of the worldwide drone data services industry. It is anticipated that the market for photogrammetry software will expand significantly and reach $1.4 billion by 2024.

• Growing Demand

To improve surveying accuracy and efficiency, engineering organizations are progressively combining photogrammetry with drone technology. The growing demand for drone-based photogrammetry solutions is shown in the over 60% of businesses that expect to implement this integration by 2024.

• Technological Developments

Improving automation, advancing sensor and camera technologies, and incorporating artificial intelligence and analytics tools will be the main areas of future development in drone photogrammetry. I believe these developments will improve data-collecting capabilities, expedite workflows, and allow quicker and more precise data processing.

• Growing Uses

Drone photogrammetry finds applications in a wide range of industries, including civil engineering, real estate, filmmaking, and construction. Its adoption across several industries is fueled by its ability to facilitate better planning, decision-making, and environmental knowledge.

• Comparing photogrammetry with LiDAR

Although both methods are useful for 3D mapping, photogrammetry has several benefits over LiDAR. For large-scale projects in particular, photogrammetry proves to be economical and visually stimulating because of its exceptional ability to capture textures and hues. On the other hand, LiDAR is the method of choice for exact measurements and dense point clouds, which are perfect for accurate work.

Drone photogrammetry has a bright future ahead of it that will be marked by innovation and the integration of new technology. Drone photogrammetry will change industrial processes as technology develops further, providing advantages including high accuracy, increased safety, cost savings, and quicker data collecting and analysis. Drone photogrammetry is positioned to have a significant influence on how data is collected and analyzed, and decisions are made in a variety of industries going forward thanks to developments in automation, sensor technology, and AI integration.

Conclusive Remarks

As we approach the end of our thorough examination of drone photogrammetry, it is clear that this technology is more than just trendy; it is a game-changer for aerial data collection. Its versatility and effectiveness, which provide unparalleled accuracy and insights, have made it vital in a variety of sectors. Drone photogrammetry is on a bright trajectory, with potential developments that will improve its accuracy and accessibility despite obstacles and regulatory difficulties.

Drone photogrammetry, which is at the forefront of innovation, has the potential to completely change how we see the world and how we interact with it by opening up previously undiscovered territories. With any luck, this guide will provide you with the necessary understanding and information to traverse this ever-changing field and begin your journey toward the limitless possibilities of drone photogrammetry.