HAVING spent numerous years as a forest surveyor undertaking a traditional, terrestrial approach to gathering information about our woodland environments, it often occurred to me – is this the best way to apprehend such landscapes?
Following many hours of research, it became clear that there are more high-tech approaches that can be taken. Using UAVs (unmanned aerial vehicles) can solve practical challenges faced by forestry managers, land managers, practitioners and contractors alike. After numerous in-depth conversations with my brother, a fellow forester who had recently visited the ‘Drone Zone’ at Elmia Wood in 2017, we became convinced of the potential behind gathering highly accurate geospatial data through aerial imagery. This began the inception of Artio Geomatics.
As a smaller business, we set our sights on alternative approaches that combined UAV outputs with established geospatial measurement techniques to interpret the forest and wider landscapes.
Enlisting the expertise of David Parker – an experienced and fully qualified commercial UAV pilot – we were able to combine our collective knowledge of surveying, mapping and GIS (geographical information systems) with his expertise in remote sensing techniques and point cloud modelling to create a powerful and useable service backed up by an experienced team of professionals.
Now for the technical bit – we use digital aerial photogrammetry (DAP) to create spatially continuous 3D information from digital aerial images gathered using UAVs. 3D data, i.e. point clouds or digital elevation models (DEM), are extracted from overlapping images by means of image matching. Common features in multiple images can then be localized in 3D space to create an orthomosaic. Put simply, an orthomosaic map is a detailed, accurate photo representation of an area, stitched together and geometrically corrected (orthorectified) so that it is as accurate as a map.
The move into the world of photogrammetry and 3D modelling has provided a fascinating and welcome challenge. Through extensive testing of software and flight scenarios together with rigorous field tests we have great confidence in the deliverables we can offer – whether they be practical 2D maps, impressive 3D models or a full range of GIS-compatible outputs.
Starting with the customer, we work closely with our clients to talk through the project, identify the required outcomes and design a bespoke package based around our four key services:
FeatureMapper – Using UAVs to gather nadir (top-down) imagery of features, our team render a precise, geotagged 3D model which can be interrogated to gather accurate geospatial data. Invaluable for planning and recording attributes for any structure, tree, road or general infrastructure.
SiteMapper – With intelligent flight planning, our team can capture imagery for sites of any size. This provides an exceptionally cost-effective method of collecting large amounts of geospatial data.
TopoMapper – Highly detailed contour maps, down to 0.5 m accuracy, are created from the UAV imagery. Such topographical data is essential for reference in drainage works, site planning, infrastructure projects, erosion control and many other aspects of land management.
ForestMapper – Developed for surveying compartment boundaries, tree damage and windblow modelling, stocking density analysis, canopy closure or stand stratification. Remote surveying also allows our teams to assess inaccessible or dangerous areas in complete safety.
Once a package of work has been agreed, the appropriate permissions will be sought and any potential hazards or constraints to the mission assessed to create the all-important flight plan.
This plan includes the precise path and boundaries of the flight, the altitude of the UAV, the angle of the camera relative to the ground, the frequency of image capture and the flight speed. All of these instructions combine to influence the quality of the images taken, and therefore the overall quality of the 3D model. Finding the correct combination of flight instructions for the situation is essential for a high-quality model and subsequent analysis.
It is fair to say that the use of UAVs to gather information about our environment has been an important and exciting advancement in the world of forestry and land surveying. The models created contain vast amounts of data, presenting a plethora of beneficial applications for forestry managers when considering some or all of the following:
• ground prep assessment
• fence line assessment
• natural regeneration and restocking monitoring
• tree species classification
• stand/compartment mapping
• precise quantification of canopy coverage and nett area assessment
• nesting birds surveys
• windblow assessment and volume estimation
• harvesting operations planning
• tree crown assessment
• fire/flood/adverse weather damage assessment
• diffuse pollution monitoring
• pest/disease monitoring
Using UAVs to gather data also presents several major practical advantages over traditional field and remote sensing techniques:
Flexibility and autonomy – By creating a bespoke flight plan, the model can be focused on a particular attribute or area of a site. Imagery can also be acquired far more frequently than satellite or aircraft imagery, producing a contemporary and detailed picture of the landscape.
Affordability and high reliability of results – UAV surveys produce detailed mapping over larger areas than would be achievable with ground surveys, saving time and reducing risk to field operatives.
Production of high-resolution data – Using UAVs equipped with the right digital sensors means the images that are ‘stitched’ together are exceptionally high resolution, enabling the identification and monitoring of specific tree species, canopy gaps, forest loss, damaged and fallen trees, degradation and regrowth processes.
These technologies represent the future and natural next step for many areas of the surveying industry. Pace of innovation is a constant factor, with even the juggernaut UAV company DJI playing catch-up – with their own real-time digital land mapping software being released in May 2019. This just goes to show the importance of specialised research, knowledge and experience in such a niche field.
Thomas Fox
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