Contour Visualization
Generate topographic contour lines and cut/fill overlays to read your terrain at a glance. This tutorial covers enabling contours, interpreting line types, tuning intervals and resolution, and using the cut/fill overlay to visualize earthwork.
Prerequisites
Contour visualization works on any site with terrain — but there are a few things to have in place first.
- A site with a site area defined (see Your First Site).
- Terrain within the site area. There is always some — worldwide terrain sits under every site — so contours work before you have edited or imported anything.
- If you want the contours to reflect your edits (from brush tools or AI-generated grading), make sure Include Patches is checked in the contour settings — it is on by default.
SiteCAD's elevation stack has Cesium World Terrain at the bottom. Your terrain layers sit above it, and ground you have edited on a layer overrides what is underneath at exactly those spots. Contour generation can include or exclude those edits — toggle Include Patches to compare "before and after" your grading. (The checkbox keeps its older name; what it controls is your terrain edits.)
Enabling Contours
Contour lines are toggled from the status bar at the bottom of the editor.
- Look at the status bar at the bottom of the viewport. Find the Topo chip — its name sits beside an "On" or "Off" state.
- Click the On/Off state to turn lines on. The first time you enable contours, SiteCAD samples elevations across your site area and generates contour lines — you'll see a brief loading spinner.
- Click the Topo name to open the Contours popup, which holds Opacity, Resolution, and Include Patches — adjust them here without closing the popup.
Contour generation runs in a Web Worker so it won't freeze the editor. For large sites or high-resolution settings, generation may take a few seconds. You can continue working while it computes — contour lines appear as soon as they're ready.
Contour Line Types
SiteCAD draws three types of contour lines, each representing a different elevation interval. Understanding them lets you quickly estimate elevations and slopes.
Minor Contours
The finest lines, drawn at every minor interval step. They show detailed elevation changes and are most visible when zoomed in close. Use them to spot subtle grade changes.
Major Contours
Thicker, more prominent lines at every major interval step. They provide the primary visual rhythm of the terrain and are readable at mid-range zoom levels.
Index Contours
The boldest lines, drawn at every fifth major interval. On a topo map, these are the lines you'd label with elevations. They anchor your eye and let you count elevation differences at a glance.
With default settings (1 m minor, 5 m major), each index contour represents a 25 m elevation change. Count the index lines between two points and multiply by 25 to estimate the total elevation difference.
Intervals & Resolution
The contour settings popup lets you control how detailed and how accurate the contour lines are.
Opacity
Controls how visible the contour lines are over the base imagery. Lower opacity lets terrain textures and satellite imagery show through. Raise it when you need to read contour lines clearly.
Resolution
The spacing of elevation samples used to generate contour lines. Lower values produce smoother, more accurate contours but take longer to generate. Higher values are faster but may miss small terrain features.
Include Patches
When enabled, contour generation factors in your terrain edits (brush strokes, AI-graded surfaces). Turn it off to see contours of the original base terrain only — useful for before/after comparisons.
For quick overviews of large sites, use 2–5 m resolution. When you need to verify grading around a building pad, drop to 0.5 m for the most accurate lines. SiteCAD regenerates contours automatically when you change this setting.
Reading Contours
Contour lines are the universal language of terrain. Here are the patterns to look for when interpreting them.
Closely Spaced Lines
Lines packed tightly together indicate a steep slope. The closer the lines, the steeper the grade. If you see contour lines practically touching, you're looking at a near-vertical face.
Widely Spaced Lines
Large gaps between contour lines mean gentle terrain — nearly flat or very gradually sloped. Good areas for building pads, roads, and drainage collection.
Concentric Circles
Closed loops that nest inside each other indicate a hilltop or depression. If elevations increase inward, it's a hill; if they decrease inward, it's a basin or pond.
V-Shapes
V-shaped bends in contour lines that point uphill indicate a valley or drainage channel. Water flows in the direction the V opens. This is how you trace natural drainage paths.
Parallel Lines
Evenly spaced parallel lines mean a uniform slope — constant grade in one direction. Ideal for identifying where cut/fill transitions will occur.
Flat Pad (Flattened Area)
A sudden gap in contour lines surrounded by closely spaced lines indicates a flat terrace or graded pad. After using the Flatten brush, this is exactly the pattern you should see.
Turn on contours, then zoom into terrain you've edited with the brush tools. Match what you see in the contour lines with the 3D shape of the terrain. The more you do this, the faster you'll read contour patterns naturally.
Cut/Fill Overlay
The cut/fill overlay visualizes where earth has been added (fill) or removed (cut) relative to the original terrain. It's the fastest way to see earthwork impact.
- In the status bar, click Cut/Fill to toggle the overlay on and off — it's a plain toggle with no popup of its own.
- For the settings, click Terrain in the status bar to open the layer panel, then check Cut/fill overlay — the same toggle, with opacity and ramp controls that appear once it's on.
- The overlay only draws for layers that are visible and have Cut/fill enabled (a per-layer checkbox in Edit Layer, on by default). If the toggle is on and you see nothing, check those first.
- With the default Dirt ramp, ground you have raised above its original elevation appears in light earth tones, while ground you have lowered appears in dark soil tones.
- Unchanged areas (within the per-layer threshold) remain transparent, so you see your base imagery underneath.
This legend shows the default Dirt texture ramp. Switch to Linear color and fill/cut render as a red-brown-to-blue gradient instead, or Stepped contour for banded versions of the same. Pick the ramp in the Terrain panel, next to the overlay toggle.
Overlay Settings
The cut/fill overlay's settings live in the Terrain panel, next to its checkbox — there's no arrow or popup on the status-bar chip itself. The threshold is the one exception: it's set per layer, in Edit Layer.
Opacity
Controls how visible the cut/fill colors are. Lower opacity blends them with the satellite imagery below. At 100%, the overlay completely covers the base imagery wherever there is cut or fill to draw. Set in the Terrain panel.
Ramp Mode
How the cut/fill difference is colored: an earthwork dirt look, a smooth red-brown-to-blue gradient, or stepped contour-like bands. Set in the Terrain panel, next to the opacity slider.
Threshold
Elevation differences smaller than this are treated as zero — no cut or fill shown. Set per layer, in Edit Layer (the pencil icon on a layer row) — not on the status bar or the Terrain panel. Raise it if you see noise from tiny rounding differences; lower it for precision grading work.
Contours and the cut/fill overlay are independent imagery layers — you can enable both at once. Whichever you turn on last renders on top; there's no fixed order between them.
Practice Exercise
Try this exercise to build comfort with contour interpretation and the cut/fill overlay.
Read and Verify Your Grading
- Open a site with some grading on it. If you completed the Terrain Brush Basics exercise, use that same site.
- Enable Topo contours from the status bar. Set resolution to 0.5 m for the most accurate lines.
- Zoom to a flat area you graded. Confirm you see a wide gap in contour lines — this verifies the pad is level.
- Look at the edges of the pad. Are the contour lines tightly packed? That's the transition slope. Zoom in to check that it looks reasonable.
- Toggle Include Patches off. Notice how the contours change — you're now seeing the original terrain. Toggle it back on to compare.
- Enable the Cut/Fill overlay. Find the cut and fill areas around your pad — fill where you raised terrain, cut where you lowered it.
- With both contours and the cut/fill overlay enabled, trace a drainage path: find the V-shaped contour bends and confirm the Vs point uphill, then follow the direction they open — that's the way water runs.
- Switch the cut/fill ramp from Dirt texture to Stepped contour in the Terrain panel, and read the banded cut/fill levels. Then raise the layer's Threshold in Edit Layer and watch small noise drop out of the overlay.