Mapping Roundabouts: Precision and Art with Lidar

By Randy Allen, Senior Survey Project Manager and Lidar Mapping Manager, ESP Associates, Inc.

Let’s be honest: not many people get excited about roundabouts. But I sure do!

I’ve developed a passion for mapping these complex intersections. To me, every roundabout is a unique puzzle. There’s a rhythm to the traffic flow, an artistry in the geometry, and a challenge in the subtle slopes that test both the technical and creative sides of my work. I love capturing them in all their detail.

To the untrained eye, it’s just concrete and asphalt. I see a piece of functional sculpture; elegant curves designed to gently guide vehicle traffic, carefully banked slopes that shed water, and designs that ensure a grandmother can cross safely. It’s a microcosm of civil engineering; capturing it perfectly is my kind of art.

The Roundabout’s Riddle: Where Precision Becomes Art

Roundabouts are special. They concentrate multiple layers of design into one compact form: approach geometry, truck aprons, pedestrian flows and drainage all wrestle for the same space.

Every slope matters. Every transition has a purpose.

This is where the technical and creative must align. The technical side ensures the geometry is captured correctly. The creative side interprets how that geometry moves and interacts. You have to visualize how a driver navigates a curve, how a pedestrian reads a crosswalk, and how stormwater finds its path.

You are, in essence, reverse-engineering the experience. The map becomes a script for movement, and you have to read it like a choreographer. “The driver’s eye will be drawn here.” “A bicyclist will need this much space to merge.” “The water must go here.” This empathy for the end-user is a creative act, translating static points into a dynamic, human-centered story.

When those two sides click, the result isn’t just a digital model. It’s a meaningful representation of how people, vehicles, and water behave in that space.

I map not only what the roundabout looks like—but how it behaves.

Mapping: The Foundation for Smart Decisions

In the geospatial world, terms like processing, surveying, extraction and mapping are often used interchangeably to describe pulling information from lidar. For this article, I’ll use the term mapping as my personal description of the art and science of capturing real-world roadway features and translating them into clean, accurate CAD datasets.

These deliverables are the bedrock for engineers, designers, and planners. Whether we’re capturing pavement edges, curb returns, or drainage flowlines, the goal is the same: provide trustworthy data that clearly communicates how the roadway is built and how it functions.

We’re not just recording what exists—we’re building the foundation for what happens next.

• Good mapping allows engineers to explore design options.


• Great mapping reduces questions, uncertainty, and rework.


• Exceptional mapping—the standard I strive for—enables efficient, confident progress.

The Dance of Data and Intuition

My workflow is a blend of high-tech data collection and trained human interpretation.

The Tech: High-accuracy RIEGL lidar captures the roadway in millions of precisely measured points. This point cloud is dense enough to reveal every nuance:

• The exact roll of a truck apron


• The true edge of pavement, despite weathering or patchwork


• A subtle slope break where water shifts direction


• The gentle curvature of a pedestrian refuge island

The Translation: TopoDOT mapping software then allows us to organize, assess, understand, and translate that data into features and surfaces that engineers can use with confidence.

But tools alone don’t make a map. Experience teaches the eye. Repetition builds intuition.

Where Human Insight Matters

A novice technician sees a chaotic cloud of points. An experienced mapper sees surfaces, planes, and purpose. I don’t just follow the data—I read it.

I can trace a flowline by understanding why the water is being directed there, detect the subtle “ghost” of the original pavement beneath a new asphalt patch or notice subtle wear patterns shaped by traffic. Every slope, curve, and transition tells a story about how the space is used and interacts with stormwater, vehicles, and pedestrians.

This isn’t something a filter or algorithm can do. It’s a human skill—a conversation between the as-built reality and the digital model. My eyes and intuition interpret the intent behind the design, translating raw measurements into actionable insights.

That interpretive step is where the art lives. I’m not just seeing a point cloud—I’m understanding the roadway.

Clarity is the Ultimate Goal

A well-mapped roundabout shouldn’t feel cluttered. It should feel intentional. Every line, elevation label, and breakline must serve a clear purpose.

Good mapping communicates. Great mapping communicates quickly.

If an engineer can open the file and immediately identify controlling elevations, pedestrian paths, and grading constraints, the map has done its job. Delivering that kind of clarity is deeply satisfying.

There is an elegance in a map that is truly clear. It doesn’t shout; it guides. The goal is to create a deliverable so intuitive that the engineer’s or designer’s focus never breaks. They can simply think and design, because the map has already answered all their questions.

This is my mantra: Clarity is the art. Structure is the craft. Precision is the responsibility.

Quality is a Team Sport

This work is not a solo effort. It’s teamwork.

While we follow proven workflows for consistency, we also encourage curiosity, critical thinking, and visual reasoning. Together, we produce dense, reliable DTMs and clean, purposeful mapping that engineers trust.

Quality isn’t accidental. It’s intentional. It’s taught. And it’s shared.

Why Roundabouts Matter to Me

Ultimately, mapping roundabouts is about more than the maps themselves. It’s about combining technical expertise with creativity and producing deliverables that have real-world impact. It’s about seeing every curve, slope, and island captured accurately and knowing that the work directly influences roadway design, safety, and efficiency.

Roundabouts are living geometry.

• They shape how people interact with the roadway.


• They calm traffic.


• They protect pedestrians.


• They encourage flow over force.

For me, roundabouts are more than just intersections—they’re a canvas.

They’re where technical precision meets creative problem-solving.

Turning dots into deliverables — it’s what I do.

He also shares his passion as an Adjunct Instructor at Vincennes University, teaching the world’s only college-level TopoDOT lidar mapping software course. When he’s not mapping or teaching, Randy enjoys traveling with his wife and spoiling their first grandchild.