A Guide to Drone Data: Outcomes and Results in Surveying - COPTRZ

A Guide to Drone Data: Outcomes and Results in Surveying

Tom Garnett

12:38 pm GMT •

August 27, 2021

10 minute read

PWC suggest that by 2030, the UK could see as many at 76,000 commercial drones in our skies, generating a net cost savings of over £16bn across multiple industries.  The exponential growth in drone technology positions them as an essential tool for many organisations looking to develop their workflows and reduce costs.

A prime example of the positive impact is in the surveying and construction sectors, serving as a cost efficient and versatile means of collecting vital information. In this blog we’ll explore the different types of outcomes that can be gathered by drone technology and how this can lead to reduced costs when compared to traditional methods.

In this blog we’ll cover

  • What is Aerial Photogrammetry?
  • Topographical & Mapping Surveys
  • LiDAR Point Cloud
  • DEM
  • Drones and BIM
  • Stockpile volumetric measurements
  • Contours

Surveying with Drones

To begin with, let’s cover the key benefits drone based surveys provide;

1. Reduced field time and Survey costs  

Capturing survey-based data with a drone is up to 80% quicker than traditional methods, requiring less resources and time on site. Ultimately drone surveys deliver faster results at a lower cost.

2.  Map inaccessible or dangerous sites

An aerial mapping drone can take off and fly almost anywhere. You’re no longer limited by unreachable areas, harsh terrains and dangerous sites unsuitable for traditional methods. You no longer need to close down busy sites, in fact you can capture data during operation without an interruption to day to day operations.

 3. Provide accurate an extensive data

 When equipped with survey grade GPS (RTK/PPK) and suitable ground control, drones are able to deliver incredibly accurate and repeatable results. Drones such as the DJI Matrice 300 RTK take this one step further and can record previous flight paths, allowing for longitudinal inspection of critical assets and volumetric measurements.

 4. An accessible means of collecting data

Gone are the days when you needed a degree and years of experience to understand how to fly a drone. Having learnt from the consumer market, companies such as DJI have designed their user interfaces and fly controls to be a simple as possible, reducing the learning curve and ensuring organisations can quickly integrate drones into their workflows. The key to operating drones is understanding the laws and licenses required to operate in your country.

What is Aerial Photogrammetry?

To better understand how drones can be used in surveying, lets refresh your memory on aerial photogrammetry. This involves taking multiple aerial images of a feature or site and using them to create digitized high resolution 2D or 3D models from which accurate measurements can be deduced. This can be completed with specialised post processing software that looks for features in images and stitches them together in a way that offers an accurate representation of a space, which can be used later when off-site.

Topographical & Map Surveys

Many of you will already know what a topographical survey is, but for those who don’t a topographical survey, topo or terrain survey is a vital component in the design process for a site and should be commissioned before any detailed design works take place. A topo survey can be used as a legal document to define the boundaries of a property, or professionals such as architects, civil engineers and planners may use them to make decisions on design and project management.

Drones have become an essential tool for surveyors wanting to create accurate topos over large areas. Post processing data such as DJI Terra can stitch together hundres if not thousands images captured by your drone to create highly detailed.

LiDAR Point Clouds

 LiDAR, which stands for “Light detection and ranging” is a technology that’s been used by surveyors for many decades, yet recently it’s become increasingly popular with unmanned aerial surveys. A LiDAR sensor sends out a pulse of laser light and measures the time it takes for the pulse to return as they bounce back. A survey-grade accurate 3D point cloud of buildings or a high-rise apartment block can easily be created with a drone using photogrammetry or LiDAR. The point cloud produced from a drone can also be combined with terrestrial laser scanning surveys to produce complete 3D point clouds. These models can be imported into BIM or CAD software so that comparisons can be made with the design models.

LiDAR point clouds have also developed significantly in recent years, with payloads such as the Zenmuse L1 enabling RGB images to be captured simultaneously to the LiDAR, enabling even greater clarity and insight for your missions’ results.

Drones and BIM

 Drone technology and BIM construction technology are often conflated because they are typically used together in complex building projects. However, these two technologies perform quite different functions.

Drone technology is primarily used to take and analyze detailed photographs, videos, and laser scans of a construction site—a process called reality capture. Through this process, architects and building planners can ensure that a building fits into the contextual environment, identify potential construction challenges, and track project progress. BIM construction software, on the other hand, creates accurate 3D models of buildings from reality-capture data so that architects can plan a project from start to finish. The features and tools of BIM software vary from brand to brand, but most include the ability for project teams to collaborate in the cloud, create construction documents, and integrate with Virtual Reality (VR).

After drone images and scans from a building site are analyzed, BIM construction technology provides the project team with an even better understanding of the project’s scope and context. Drones essentially play the role of data suppliers for the BIM construction software, feeding the software information about existing site conditions to ensure that the digital 3D model created through the BIM software is as accurate as possible.

 

Stockpile volumetric measuremnts 

Using drones to calculate stockpile measurements makes it easy to compare your current stockpile volumes to previous surveys and track site progress. You can also compare stockpile surveys to a final grade design file to calculate how much material you still need to add or remove.

With geo-referenced images captured by a drone flying above your worksite, you can use photogrammetry to generate a 3D map of your site with measurements accurate to 1/10ft (3cm). By flying a drone to measure stockpile volumes instead of sending someone out to traverse a dangerous site, site management can track their inventories and site progress in a faster, safer, more reliable way.

Contour Lines and Drone

What are Contour Lines?

Contour lines are generated by connecting all the points of similar elevation together. These lines are drawn on a plan of a particular terrain to understand the nature of surface, identify cut fill volume, study water flow characteristics, estimate valley depth and steepness. Contour lines form a smooth curve of same elevation points.

Drones are used to collect the data in the form of High quality images. The complete captured data is aligned by aerial triangulation. The aligned data is then ortho-rectified and georeferenced using the GCP information. Subsequently, the final Digital Elevation Model (DEM) and Contour lines at required elevation change are generated.

What are the key uses of Contour lines?

  • Contour lines are generally used to understand the terrain profile for multiple uses as follows:
  • Depth of cutting and filling is decided from a contour map profile path, when desired level or elevation of road/railway is known
  • Minimizing and balancing earthworks by deciding the routes of the railway, road, canal or sewer lines using contour lines
  • Catchment area and quantity of water flow at any point
  • In agricultural work, contours maps are useful as guide lines in planning of trees on hilly terrain and also land improvement project. I
  • Initial feasibility study for Wind power or Solar Power project, for studying the terrain profile
  • Initial feasibility study for Ropeway construction, a survey needs to be done to analyse the terrain.
  • Volumetric calculations are performed as required for extracting the volume of rocks, gravel of a mountain and estimate it’s total value.
  • Contour lines are also benificial for Mining companies especially for calculating the volume of stocks
  • Archaeological surveyors are using contour lines to get insights about history

 

 

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