SUMO Air Space - Your Questions Answered
- Claire Rose
- Jul 3
- 4 min read
The latest from, providing a range of aerial and geospatial surveys using drones, known commercially as UAS (Unmanned Aircraft Systems).
Ask the Audience!
It is important to us that you are as informed as possible when commissioning a drone survey to make sure you know exactly what you can get out of it.
Your Questions Answered
Please see a selection of questions below that we are frequently asked ahead of our surveys.
What is multispectral and how does it work?
In brief, multispectral uses a sensor array which collects images at different wavelengths. These images can be processed to identify the health of plants on the surface. Since plant health can be influenced by sub-surface features, multispectral surveys can show where these features are by the appearance of the plants in the processed image. Therefore, archaeology or geological anomalies such as solution features, may still be revealed by drone multispectral mapping, even if they don’t leave a topographic footprint.
What level of accuracy can you achieve with your georeferencing, particularly over large landscapes?
We typically aim for a georeferencing error of <3 cm. On projects which require even tighter accuracy, we can combine our data with a traditional topographic survey.
What solution can you offer for obtaining ground levels beneath tree canopies where photogrammetry cannot reach?
We frequently collaborate with SUMO’s traditional topographic department. Where tree canopies obscure the surface, a terrestrial topographic survey can be used to fill in the gaps. Alternatively, we can carry out drone-based LiDAR which has the potential to penetrate vegetation.
Is photogrammetry better than LiDAR?
Each of these survey methods has its place, depending on the requirements of the project. As above, photogrammetry is preferred for open sites whereas LiDAR is better for penetrating vegetation, particularly woodland, through which it can capture ground levels beneath the canopy.
What are the optimum conditions for a drone survey?
In order to operate safely, it is important that we carefully consider the weather for every job we carry out. Generally, we aim for days which are dry with low winds and proceed only if it’s practicable to do so. Very often, we only find out what the weather will really be like when we arrive on site.
Each of our survey methods have further nuances to encourage the best results.
RGB photogrammetry works best with little shadow cast over or across the subject; multispectral photogrammetry is most effective within a two hour window either side of midday; thermal building surveys are best carried out at night when there is no solar radiation interference, whereas thermal solar farm inspections require high levels of solar irradiance during the day to be successful.
How quickly can you go from instruction to delivery of results?
Since drone surveys are dependent on the ever-changing weather forecast, we are very used to attending site with little notice. We always aim to meet specific dates as provided by the client and make contingencies for the weather when necessary. Initial outputs (e.g orthophoto, Digital Elevation Models, and 3D model) are provided within 2–5 days of the survey, and we usually allow up to 4 weeks for the interpretive report. However, from time to time a faster turnaround is required for which we always strive to meet pressing deadlines.
Can you operate in restricted airspace?
In short, yes, we can operate in most restricted airspace. Prior to supplying a quote, we check to see what airspace your site falls in as this may have a bearing on when we can carry out the survey. It is a legal requirement, governed by the CAA (Civil Aviation Authority) to ensure that we seek permission to fly in restricted airspace, such as FRZs (Flight Restriction Zones) for airfields, prisons, and military bases. There are few instances where drone operations are not permissible, however we are aware of these locations and can make alternative arrangements if required.
Can you carry out earthwork surveys for planning conditions?
Absolutely, a photogrammetry survey is the ultimate tool for identifying topographic and micro-topographic features across a site. The outputs include an orthophoto and DEM (Digital Elevation Model), the latter of which can be manipulated in GIS software to analyse the site, and an interpretive report can be drawn up to show the findings.
Are drone surveys effective for topographic surveys?
Since drones can map <100ha in a single day and achieve a ground error of <3cm, this method is the perfect tool for topographic surveys. Drone surveys are particularly impactful over areas which are not accessible on foot, such as busy construction sites and roads.For the most accurate results, we can combine the data with a terrestrial topographic survey to tighten the referencing, saving land surveyors time on site, and therefore reducing the cost of the survey.
Can drones be used inside buildings, such as churches?
Yes, drones can be operated inside buildings. We have conducted photogrammetry, and general video and photos from within buildings including churches.
What outputs can you provide from a building survey?
Photogrammetry surveys can produce a range of deliverables, depending on the needs of the client. Standard outputs include scaled orthorectified elevations and roof plan, and a link to a low-resolution 3D model for online viewing. Further outputs include a point cloud, high-resolution 3D model files, all survey photographs, general video, and panoramic spheres. In addition, we can combine our outputs with laser scan data as part of a detailed Measured Building Survey.
