GIS-Based Site Analysis

GIS-Based Site Analysis refers to the use of Geographic Information Systems (GIS) to evaluate land, rooftops, terrain, and environmental conditions for solar PV development. GIS allows solar engineers, developers, EPCs, and installers to assess site viability using spatial data layers such as elevation models, slope angles, azimuth, land boundaries, utility proximity, environmental constraints, and shading features.

In modern solar workflows, GIS-based analysis is essential for both rooftop and ground-mount projects. It helps identify the most productive installation zones, avoid restricted areas, optimize array placement, and ensure compliance with permitting and environmental requirements. Tools like SurgePV incorporate GIS intelligence throughout the design workflow, especially within Solar Designing and Solar Project Planning Analysis.

Key Takeaways

GIS-Based Site Analysis uses spatial and geographic data to evaluate solar feasibility and optimize layout.
Essential for rooftops, ground mounts, commercial buildings, and utility-scale sites.
Helps identify constraints early, reduce redesign, and improve modeling accuracy.
Integrates with shading, irradiance, terrain, and environmental data.
Forms the foundation of accurate and scalable solar design workflows such as SurgePV’s Solar Designing.

What Is GIS-Based Site Analysis?

GIS-Based Site Analysis is the process of using spatial data and geospatial tools to evaluate where a solar array can be installed and how efficiently it will perform. It brings geographic, engineering, environmental, and structural data together to inform design decisions.

GIS datasets commonly include:

Roof outlines and building footprints
Parcel boundaries
Topographic maps and contour lines
Vegetation height and surrounding obstructions
Slope and aspect data
Setbacks and zoning constraints
Utility networks and interconnection points

GIS enhances decision-making by providing site-specific, layered, accurate information that removes guesswork during solar development.

Related terms include Topographic Analysis, Irradiance Mapping, and Shading Analysis.

How GIS-Based Site Analysis Works

1. Collect Spatial Data

GIS software imports various map layers: satellite imagery, LiDAR, property lines, contours, zoning maps, flood zones, and more.

2. Analyze Terrain Characteristics

This includes:

Slope percentage
Elevation
South-facing exposure
Shading objects

Terrain optimization is especially important for ground-mounted systems.

3. Identify Usable Installation Areas

GIS defines buildable zones by removing:

Wetlands
Floodplains
Setbacks
Property boundary conflicts
Steep slopes
Vegetation obstructions

This functions similarly to applying an Array Boundary Tool.

4. Incorporate Irradiance & POA Calculations

GIS integrates solar resource maps to evaluate site-specific yield.

See POA Irradiance.

5. Design Optimal Layout

GIS feeds data into layout tools like SurgePV to generate optimal panel placement, stringing, and system modeling within Solar Designing.

6. Evaluate Interconnection & Access Routes

GIS maps utility lines, substations, service roads, and easement paths.

7. Export Data to Project Planning

GIS outputs feed proposal tools, permitting workflows, and engineering processes through the Solar Project Planning Hub.

Types / Variants of GIS-Based Site Analysis

1. Rooftop GIS Analysis

Used to map building footprints, setbacks, obstructions, roof angles, and shading from nearby structures.

2. Ground-Mount GIS Analysis

Evaluates land contours, terrain slope, environmental restrictions, and buildable zones.

3. Utility-Scale GIS Assessment

Includes transmission proximity, land availability, environmental overlays, and large-scale shading studies.

4. Environmental GIS Layers

Flood risk, wetlands, protected species habitat, soil stability, and erosion patterns.

5. Urban GIS Mapping

Used for commercial and industrial properties in dense cities.

6. AI-Enhanced GIS

Machine-learning classification of land cover and rooftop features from imagery.

How It's Measured

GIS analysis is typically quantified using:

Slope (degrees or percent)

Determines whether the land can support a stable or efficient solar layout.

Aspect (direction of slope)

Critical for maximizing production on sloped terrain.

Usable Land (acres / sq ft)

Net buildable area after exclusions.

Solar Irradiance Levels (kWh/m²/day)

Used for energy production modeling.

Setback Zones (ft or meters)

Mapped visually to avoid encroachments.

Shading Metrics

Vegetation height, seasonal shading, horizon profiles.

Tools like SurgePV assist in integrating GIS data into shading and irradiance workflows, especially with Shadow Analysis.

Typical Values / Ranges

Slope Tolerance

Rooftop: Follows building geometry
Ground-Mount: Typically < 15% slope preferred
Utility-Scale: < 8% slope ideal

Buildable Area Ratios

Residential rooftops: 40–70% usable
Commercial rooftops: 60–90% usable
Ground sites: 20–80% usable depending on terrain

Irradiance Thresholds

Strong solar regions: 5.0–6.5 kWh/m²/day
Moderate climates: 3.5–5.0 kWh/m²/day

Vegetation Buffer

2–10 meters depending on tree height

Practical Guidance for Solar Designers & Installers

1. Start every large project with GIS before designing

Identifies land-use issues early and reduces redesign time.

2. Use LiDAR when available

Produces highly accurate rooftop and terrain models.

3. Exclude restricted zones immediately

Wetlands, property boundaries, rights-of-way, and setback zones must be removed before layout.

4. Incorporate shading into GIS

Combine spatial analysis with Shading Analysis for accurate production results.

5. Use GIS to automate initial layouts

Feed GIS boundaries into Auto-Design, improving panel placement efficiency.

6. Check utility proximity for interconnection feasibility

Transmission and distribution connection distances are often the biggest cost drivers.

7. Include GIS outputs in proposal workflow

GIS maps improve customer clarity when generating proposals using Solar Proposals.

Real-World Examples

1. Residential Rooftop GIS Assessment

GIS identifies usable surfaces on a multi-facet roof, excluding chimneys and shading from nearby trees. The model supports a 7 kW layout with minimal shading losses.

2. Commercial Facility Analysis

A 300,000 sq ft warehouse is mapped using parcel data, roof pitch detection, and obstruction layers. GIS confirms 85% usable area for a large flat-roof solar array.

3. Utility-Scale Ground-Mount Project

GIS analyzes a 250-acre site’s slope, wetlands, transmission proximity, soil type, and shading. After exclusions, 140 acres are deemed buildable, supporting a 75 MW solar farm.