Topography Surveys: Purpose, Technology, and Best Practices
Table A, Optional Item #5 — Vertical Relief with Source of Information — also known as a Topography Survey, is a required scope when undertaking a new development or major renovation project. Topography is also required when a multifamily project is financed through the U.S. Department of Housing and Urban Development (HUD).
The purpose of this scope is to identify site-specific vertical and spatial information that supports engineering and architectural design.
Topography Survey Technologies: LiDAR vs. Ground Topography
Both LiDAR and ground-based topography surveys require a technician to be physically on site. Surveyors often cut lines through wooded areas to create a grid of elevation points — typically spaced every 25 to 50 feet, depending on the client’s requirements. The tighter the grid, the higher the data accuracy.
There are two main technologies used for topography surveys:
- LiDAR (Light Detection and Ranging)
- Ground Topography (Conventional Surveying)
LiDAR (Light Detection and Ranging)
LiDAR uses laser pulses emitted from airborne platforms (such as drones or aircraft) to measure distances and generate 3D terrain models. From these models, contours and spot elevations are produced.
When to Use LiDAR
LiDAR enables airborne data collection over large or challenging areas. Drone-based LiDAR can cover extensive terrain — typically two acres or more — with remarkable accuracy. It captures millions of elevation points, producing detailed Digital Elevation Models (DEMs) and Digital Terrain Models (DTMs) used by engineers and designers.
LiDAR is ideal for:
- Large tracts of land, highways, swamps, and wooded or inaccessible areas
- Terrain that is unsafe or impractical to traverse on foot
- Mapping under forest canopies or dense vegetation
- Minimizing human error and maximizing data precision
Because LiDAR automates data collection, it significantly reduces the risk of human error associated with manual surveying. It also enhances safety — surveyors do not need to physically access hazardous terrain or encounter potential dangers (e.g., animals or environmental hazards). LiDAR can capture elevation points every few inches, depending on the grid density, resulting in highly accurate surface and contour data.
LiDAR Limitations
- High initial cost for equipment, training, and processing software
- Requires specialized operators with technical expertise in data collection and interpretation
Ground Topography (Conventional Surveying)
Ground topography involves surveyors manually measuring land elevations using instruments such as total stations, Global Positioning System (GPS) units, and levels. When combined with a GPS, satellite-based navigation system, the results are highly accurate coordinates.
When to Use Ground Topography
Ground surveys are best suited for smaller sites requiring fine-grained detail, such as drainage ditches, minor elevation changes, and ADA-compliant sidewalks. Field technicians take direct measurements, ensuring high accuracy in localized settings.
Ground topography is ideal for:
- Urban or restricted areas (e.g., dense metropolitan zones, near airports)
- Small and detailed projects where LiDAR may not be practical
- Lower-cost applications with limited area coverage
Ground Topography Limitations
- Time-intensive: Surveyors must walk the site and manually collect data, making this method slower and more laborious — particularly for large or heavily vegetated sites.
- Limited accessibility: Challenging terrain (such as cliffs, swamps, or dense brush) can significantly delay fieldwork.
What to Expect When Ordering a Topography Survey
This scope is typically requested to support engineering and design or to satisfy HUD program requirements. It’s essential to communicate your project needs clearly with the surveyor at the outset so they can recommend the most appropriate methods and technologies. In many cases, a combination of LiDAR and ground topography may be used to achieve optimal results.
When adding Optional Table A, Item #5 (Topography) to your survey, expect additional costs and lead time that vary based on:
- Intend for the survey
- Property size
- Terrain complexity
- Vegetation density
- Weather conditions
The final deliverable is typically provided as a CAD drawing file, which can be seamlessly integrated into engineering and architectural design workflows.
