Drawing contour lines means different things depending on context. In art, a contour line traces the visible edges of a subject to capture its form. On maps and in geographic work, contour lines connect points of equal elevation to represent terrain. Both skills rely on careful observation and a few core rules. Here’s how to approach each one.
Contour Drawing in Art
A contour drawing captures the outline and key edges of a subject using a single, continuous (or near-continuous) line. Unlike shading-based drawing, contour drawing strips away tone and texture and forces you to really look at what you’re drawing. The goal is to translate the three-dimensional edges you see into a line on paper, following every curve, bump, and angle as your eye travels along the subject.
To start, pick a simple object like a shoe, a hand, or a piece of fruit. Place it in front of you at eye level. Begin your pencil at one edge of the object and slowly trace its outline, letting your eye move along the object’s edge at the same pace your hand moves across the paper. Draw slowly. Most beginners rush, and the result is a generic shape rather than an observed one. The line should reflect every small shift in direction you actually see.
Blind Contour Drawing
Blind contour drawing is the most common training exercise for building observation skills. The rule is simple: draw from observation without looking at your paper. Your eyes stay locked on the subject while your hand follows along on the page. The results look strange, often comically distorted, and that’s the point. The exercise breaks the habit of drawing what you think something looks like and forces you to draw what you actually see.
Start with the largest shape or object first, then work toward smaller details. If you find yourself peeking, try sliding a paper plate over your drawing hand (punch a hole for the pencil) or position your paper under the edge of a table so it’s out of sight. These tricks sound silly, but they work. Blind contour drawings build hand-eye coordination, loosen up your line quality, and help you accept imperfection. They’re also fast, usually taking just a few minutes per drawing, which makes them ideal warm-up exercises.
Modified Contour Drawing
Modified contour drawing follows the same slow, observational approach but lets you glance at your paper occasionally. You still spend most of your time looking at the subject (roughly 80 to 90 percent), but you’re allowed brief check-ins to see where your pencil is on the page. This produces drawings that are more proportionally accurate while still training the same core skill of focused observation. It’s a natural next step after practicing blind contour.
Cross-Contour Drawing
Cross-contour lines don’t trace the outer edges of a form. Instead, they wrap around it, like the lines on a topographic map draped over a 3D object. Imagine drawing horizontal lines across an apple: each line would curve to follow the apple’s rounded surface. These lines communicate volume and depth without shading. To practice, start with a simple rounded object and draw a series of lines that travel across its surface, curving to match its shape. Where the surface curves sharply, the lines will bunch together. Where it’s flatter, they’ll spread apart.
Drawing Contour Lines on Maps
On a topographic map, contour lines represent elevation. Every point along a single contour line sits at the exact same height above sea level. When you see a series of contour lines on a map, you’re looking at a way to visualize three-dimensional terrain on a flat surface. The vertical distance between consecutive contour lines is called the contour interval, and it stays consistent across the map (for example, every line represents a 20-foot change in elevation).
Rules That Contour Lines Must Follow
Whether you’re drawing contour lines by hand for a geography class or interpreting them on an existing map, a few geometric rules always apply:
- Contour lines never cross each other. Since each line represents a single elevation, two lines crossing would mean a point on the ground is at two different elevations simultaneously.
- Contour lines never split or merge. A single line doesn’t fork into two, and two lines don’t combine into one.
- Spacing indicates steepness. Lines packed closely together represent steep terrain. Lines spread far apart represent gentle slopes or nearly flat ground.
- Lines form a V in valleys. When contour lines cross a stream or valley, they bend into a V shape with the point of the V aiming upstream (uphill).
- Contour lines form closed loops. Every contour line eventually closes on itself, though the closure might happen beyond the edge of the map you’re looking at. Closed loops on the map typically indicate hilltops or depressions.
Drawing Contour Lines by Hand
If you’re creating contour lines from a set of known elevation points (a common exercise in geography and geology courses), start by plotting those points on your paper with their elevation values. Choose a contour interval that makes sense for the range of elevations, something that produces enough lines to show the terrain without making the map unreadable. For a landscape ranging from 100 to 300 feet, a 20-foot interval gives you 10 contour lines.
Next, estimate where each contour elevation falls between your known points. If one point is at 80 feet and a neighboring point is at 120 feet, the 100-foot contour line passes roughly halfway between them. Mark these interpolated positions, then connect the marks for each elevation with a smooth, curving line. Contour lines in nature are rarely straight, so draw gently curving shapes. Keep checking the rules above as you go: your lines shouldn’t cross, split, or merge.
For index contours (typically every fifth line), draw a thicker or bolder line and label it with the elevation value. This helps anyone reading the map quickly gauge the overall elevation without counting individual lines.
Generating Contour Lines Digitally
For professional or large-scale work, contour lines are generated from digital elevation data rather than drawn by hand. The most common workflow starts with a digital elevation model (DEM), which is a grid of elevation values typically derived from LiDAR scanning or satellite measurements. Software then automatically traces lines through the grid at each contour interval.
GIS platforms like QGIS (free and open source) and ArcGIS Pro both have built-in tools for generating contours from DEM data. In most programs, you load your elevation raster, select a contour generation tool, specify your interval, and the software produces vector contour lines in seconds. You can also download pre-made contour data from the USGS, which provides free public-domain contour datasets through its 3D Elevation Program. These contours are derived from high-resolution elevation data and are available in standard GIS file formats.
CAD software like AutoCAD Civil 3D follows a similar process but is geared toward engineering and site design. You import a point cloud or surface model, define your contour interval, and the software generates the lines as part of the surface object. The advantage of digital generation is precision and speed, but understanding the manual rules helps you spot errors and interpret the output correctly.