Drone Survey Planning with 3D Maps

Essential Planning Tasks for a Surveyor

Let’s first review some of the main tasks that surveyors are likely performing remotely at their desks in the office before going onsite:

The Area and Goal of the Survey will determine the type of data to be collected such as orthophotos, point clouds. This assessment is made based on the customer's requirements.

Obtain required authorization, if applicable, for your drone operation. Depending on your country, local service providers facilitate the regulatory application with your local civil aviation or other relevant authorities.

Establish safety plans and emergency procedures addressing potential issues like equipment failure, loss of GNSS signal, or unexpected obstacles.

Simulate the flight plan to identify any potential issues or inefficiencies and adjust the plan accordingly.

Understand the survey site topography, potential hazards, obstacles, regulations, and restrictions on drone flights in the area, such as no-fly zones, altitude restrictions, and active NOTAMs. This is crucial to understand if the survey is doable and under which conditions. It will also help to set the Take Of Point and the Ground Control Points locations in the survey area to calibrate and validate the drone-collected data. The surveyor needs to ensure the GCPs are visible from the air, well-distributed over the survey area, and easily reachable by the team.

Plan the flight path using your favorite survey specialized software, and optimize coverage for data collection efficiency. Consider many factors like the drone's battery life, sensor range, overlap of images, etc.

Challenges of Drone Survey Planning

Let’s dive into one of the main challenges when planning remotely, that is to understand the survey site.
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Obstacles

Using standard satellite imagery Services such as Google Earth or other services, you can potentially miss crucial details. The satellite imagery might be out of date and even when up to date, features like power lines or antennas are particularly difficult to spot. What if the satellite imagery map could be enhanced with actual digital features representing 3D objects like safety buffer zones around buildings, antennas, power lines, and more; almost like a Digital Twin of your mission zone?

Stratomaps’ 3D Buffers around antennas and power lines are illustrated below:

screenshot showing stratomaps buffer zone missing from imagery

Area with recent antenna installed (missing from imagery) / stratomaps’ buffer zones around antenna

screenshot showing buffer zones around pylons and power lines difficult to see but visible with stratomaps

Hard to spot power line / stratomaps’ buffer zone around pylons & power lines

Buffer Zones & Private Properties

To minimize the ground risk, different countries have adopted regulations that dictate the minimum distance a drone must maintain from populated areas, buildings, and other structures. At a high level, the minimum distance is usually made of distinct volumes, that is:

the flight volume: the volume the drone should not leave with contingency procedures associated such as trajectory correction, back from automated flight to manual pilot commands.

the contingency volume: the volume the drone should not enter with emergency procedures like activation of Return Home.

the buffer volume: the volume the drone should not enter with emergency procedures like activation of the Flight Termination System.

screenshot showing the flight volume, the contingency volume and the buffer volume

How large these volumes should be depends on various parameters such as the drone class, the mission type, and the aircraft glide ratio. These details, mandatory for your mission planning, can be obtained from the civil aviation authority in the country you operate in. But once you are clear on the regulatory requirements, how do you visualize these volumes efficiently?

The flight volume and contingency volume are dependent on your path and can be generated as a 3D corridor along your path as shown in the adjacent image generated using stratomaps’s technology.
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When planning drone flights, it's crucial to consider the implications of flying over private properties, and capturing images to be compliant with privacy rights. It may be necessary to contact the property owner in advance. Having access to a map with cadastral data as a custom layer overlay can facilitate the process of identifying the right person to contact.

Civil Aviation Data

To minimize risks (both Air and Ground risks), protect sensitive sites, and preserve the natural environment, country civil aviation authorities provide detailed geographical zones where prohibitions or restrictions apply, whether permanent or temporary. This includes but is not limited to:

screenshot showing a few restrictions for a specific mission zone

The map above shows, to illustrate, a few restrictions and prohibitions for a specific mission zone.

Prohibited Zones: drone flights are generally prohibited unless specific authorization is obtained.

Restricted Zones: In these zones, drones may be subject to specific restrictions. For example, drones might be allowed only up to a certain altitude or during certain times of the day.‍

NOTAMs, which can be activated on short notice. Therefore it is recommended to check NOTAM again, just before the fight starts.

Zones around sensitive sites, critical infrastructures.

Zones around natural reserves.

Having access to up-to-date restrictions or prohibitions for the mission zone while planning, allows the surveyor to make informed decisions, and seek authorization from the authorities if necessary.

Elevation Data

Ground elevation data plays an important role in assessing the most optimal Take Of Location points during the planning phase but also for automated missions with steep slopes in which you need to stay at a constant Above Ground Level altitude. This could be a photogrammetry mission where you typically do not want the AGL height to vary too much.

As an example for a 50-meter AGL flight, the maximum acceptable variation could be +/- 2 meters. Your drone is likely equipped with GNSS (Global Navigation Satellite System) systems augmented with RTK (Real Time Kinematic) technology so that you get accurate altitude above the ellipsoid altitude (or above the Mean Sea Level for orthometric height following the geoid EMG96 model). Having an accurate horizontal and vertical positioning system above the earth's ellipsoid or geoid is great but this alone is not sufficient to ensure your drone stays at a constant AGL altitude while performing its missions. You need to factor in actual ground elevation.

Screenshot showing different elevations in different colors

Most drone pilot software will propose by default to use as Digital Terrain Elevation Data the Shuttle Radar Topography Mission (SRTM) 1-arc second data provided by the US Geological Survey (USGS), which uses a vertical reference based on the EGM96 geoid model. 1-arc second means roughly that you have one elevation point every 30 meters with a vertical accuracy that decreases with an increase in slope and elevation.

This data is very useful as it allows you to conduct missions in many places around the world but it can have resolution and precision limitations in specific locations such as mountains, volcanic regions, coastal cliffs, and canyons. An alternative is to use other more accurate local Digital Terrain Elevation Data, either freely or commercially available. Based on the country, these data sets might be provided in a different vertical and horizontal Coordinate Reference System than WGS84/EGM96. The actual process of extracting and converting to WGS84/EGM96 can be cumbersome and time-consuming. Ultimately what you need is a small (in Mb size) Geotiff representing the area of your mission zone, ready to upload in your drone pilot software.

Stratomaps can generate ready-to-use Geotiff files along with customizable zone elevation visualization that can be used during the planning phase.

It is also worth mentioning that having access to accurate Digital Elevation Model is also important to ensure your drone stays under the maximum authorized regulatory vertical flight limit.

Other

Other challenging data sources can be integrated into the mission zone through APIs. It could be weather data, cellular network data, or more custom data sources pertinent to your project.

Benefits for Drone Survey Planning

Reduced costs: By avoiding unnecessary site visits, you can significantly reduce travel expenses.

Faster project completion: Planning with 3D maps means faster execution times. You spend less time planning and more time collecting valuable data, enabling you to complete projects more efficiently.

Maximum efficiency on site: No more guesswork or time-consuming scouting. 3D maps provide a clear picture of the terrain, enabling you to collect data more efficiently and maximize your on-site productivity.

Improve planning efficiency: By having access to one single interface that gathers all relevant information for your mission zone.

Informed decision-making: with 3D maps, you can make data-driven decisions on drone selection, sensor choice, and flight paths. This level of knowledge enables you to optimize every aspect of your survey, ensuring you collect the right data, in the right way.

Improved data quality: Precise planning based on accurate 3D data guarantees superior survey results. You'll capture complete data sets with fewer missing points, resulting in higher-quality deliverables for your customers.

Do you have a large area for which you need to perform surveys for agricultural, forestry, environmental, mining, infrastructure surveys, or others? Need more predictability with your mission planning? Want to avoid bad surprises once onsite? Stratomaps' 3D map services offer a new level of map accuracy and make your operations more efficient. Contact us and find out how 3D maps can help you.