Photogrammetry mapping for solar farm development

Pre-construction site assessment for solar development

Solar farm development in Ireland has grown significantly as landowners and energy companies recognize renewable energy opportunities. As Bob Foley, founder of Engineers With Drones, observes: "A lot of farmers would think, I can farm cows or I can farm sun. One of them takes a lot of energy and effort. The other one generates a lot of energy and doesn't take a lot of effort at all." Particularly for farmers with poor agricultural land but good sun exposure, solar farming presents an attractive alternative.

Solar development companies work with landowners to assess site potential before committing to construction. A solar development company engaged Engineers With Drones to map approximately 150 hectares of farmland in Ireland - a site located along a river floodplain with varied topography and active agricultural use.

The challenge was to deliver survey-grade photogrammetric data across this large, varied site with accuracy sufficient for engineering design software, within a tight timeline and budget. Traditional ground-based surveying of 150 hectares would require weeks or months of fieldwork with significant cost, and would struggle to capture comprehensive vegetation heights and terrain features across such a large area.

The client needed comprehensive topographical data to assess terrain suitability, analyze shading patterns, evaluate sun exposure, and provide input data for specialized solar farm design software. This data would determine whether the site was viable for solar development and enable detailed panel placement modeling.

Ground control strategy for vegetated farmland

Survey-grade photogrammetry requires accurate ground control points to ensure positional accuracy throughout the dataset. However, standard spray-painted ground control targets don't work effectively on vegetated farmland.

Bob Foley explains the solution: "Because we're dealing with vegetation, spray painted ground control wasn't great so we used our own custom ground control boards which were about 60 centimeters square." These custom boards show up clearly at the project's 2.2cm ground sample distance and can be positioned across vegetated farmland where spray paint would be ineffective.

Ground control was deployed throughout the 150-hectare site before flight operations, with positions surveyed to provide accurate reference points for photogrammetric processing. This ensured the final deliverables would meet survey-grade accuracy requirements for engineering software.

Flight planning and data capture

The survey was flown at 80 meters above ground level (AGL), maintained consistently throughout the site to ensure uniform ground sample distance. This altitude delivered a GSD of 2.2 centimeters - high resolution for detailed feature identification while maintaining efficient area coverage.

The survey included both nadir imagery (straight down) covering the entire 150-hectare site, and oblique imagery of hedges, tree lines, and terrain features to capture accurate height data. This combination ensures comprehensive data capture for both terrain modeling and vegetation analysis.

Bob Foley notes the importance of raw data quality: "If you're getting something good raw, that will trickle downstream to everything else." The survey used 80% front overlap and 80% side overlap - very high overlap values that ensure survey-grade accuracy and detail in processed deliverables. This level of overlap provides multiple views of every point on the ground, enabling accurate terrain reconstruction and vegetation height extraction.

Fieldwork required 2.5-3 days to capture the entire 150-hectare site at this level of detail, coordinating with landowners to ensure safe access and avoid disruption to farming operations.

Regulatory approach - open category operations

The entire project was conducted under Open Category drone operations - the lowest-risk regulatory framework available under European drone regulations.

Bob Foley explains why this was appropriate: "Projects like that are very typical of open-category projects because you're in rural farmland, you're not flying over uninvolved people, you're not flying close to built-up areas." The rural location, absence of uninvolved people, and distance from airports or built-up areas meant the project could proceed with minimal regulatory overhead while maintaining full safety compliance.

Had the site been near an airport or built-up area, specific category operations would have been required with additional permissions and safety documentation. However, the site characteristics allowed efficient open-category operations, reducing project complexity and timeline while maintaining full regulatory compliance.

Data processing and deliverables

All captured imagery and ground control data was processed into a comprehensive deliverables package designed to feed directly into solar farm design software.

Orthophoto

High-resolution orthophoto at 2.2cm ground sample distance, geometrically corrected and georeferenced. This provides a visually accurate, map-accurate representation of the entire 150-hectare site for planning and design visualization. Unlike standard aerial photography, an orthophoto has uniform scale throughout, making it suitable for accurate measurement and design work.

Topographical survey

Comprehensive topographical data captured from the photogrammetric model, including:

• Tree heights and locations - critical for shading analysis
• Hedge heights and alignments - boundary features that affect panel placement
• Walls, fences, and gates - existing infrastructure constraints
• Buildings and structures - obstacles and planning considerations
• Rivers and streams - environmental constraints and flood zones
• Roads and tracks - access route planning
• All terrain features - slopes, valleys, and elevation changes

This data is formatted for import into solar farm CAD software, enabling designers to model panel placement, electrical infrastructure, and access routes with accurate terrain and vegetation constraints.

Digital Elevation Model (DEM)

Bare-earth elevation model showing ground surface topography without vegetation or structures. This is critical for understanding terrain slopes, drainage patterns, and grading requirements. Solar panels must be oriented correctly to maximize sun exposure, and the DEM shows which areas of the site are suitable for panel placement and which require excessive grading or structural support.

Digital Surface Model (DSM)

Surface model including vegetation and structures. Used in combination with the DEM to determine vegetation heights and analyze shading patterns throughout the year. The difference between DSM and DEM heights reveals tree and hedge heights at every point across the site, enabling comprehensive shading analysis for panel efficiency modeling.

Solar farm design integration

The delivered data feeds directly into specialized solar farm CAD software that models panel placement, electrical layout, shading throughout seasons, and energy production estimates. These software packages are specifically designed to work with topographical survey data and terrain models to optimize solar farm design.

The software uses the topographical data to:

• Model panel placement accounting for terrain slopes and orientations
• Analyze shading from trees, hedges, and terrain throughout all seasons and times of day
• Calculate sun exposure and energy production estimates based on actual site geometry
• Design electrical infrastructure and access routes around existing features and constraints
• Assess environmental constraints including flood zones and protected vegetation
• Optimize panel array layouts to maximize energy production while minimizing grading and site preparation costs

Accurate input data is critical - even small errors in terrain modeling or vegetation heights can significantly impact shading analysis and energy production calculations. The survey-grade accuracy delivered by photogrammetric mapping ensures the solar farm design is based on reliable data.

Fast, accurate site assessment for renewable energy

The client received a complete survey-grade dataset within 2.5-3 weeks of project commencement - significantly faster than traditional ground surveying methods would have achieved across 150 hectares. The photogrammetric data enabled detailed solar farm design and site suitability assessment using specialized CAD software.

The comprehensive coverage of terrain, vegetation, infrastructure, and environmental features provided everything needed for solar farm design in a single dataset. Traditional surveying would have required separate efforts to capture ground elevations, vegetation heights, infrastructure locations, and visual site documentation - all delivered together through photogrammetric processing.

The fast turnaround maintained the solar development timeline, allowing the client to proceed with site assessment, planning applications, and design work without delays. The cost-effective approach to large-area mapping demonstrated the efficiency of drone-based photogrammetry for renewable energy pre-construction assessment.