If you love hiking or mountaineering, then you no doubt love exploring steep terrain and uneven ground, tiptoeing across streams without getting wet, and peering over hills and valleys when you reach the top of a climb. But have you ever thought about how to represent those natural features on a map? This is done through topography — a mapping technique also used in urban planning, civil engineering, and environmental assessment
Let’s discuss what a topographic map is, how to read one, and its role in urban and site planning.
What does topography mean?
Topography is a detailed description or representation of the natural and artificial physical features of an area. These features are often drawn on a topographic map.
What are topographic maps?
A topographic map represents a three-dimensional landscape in two dimensions. It typically shows various landforms, including peaks, valleys, ridges, rivers, and lakes. These maps can also show you whether you will be traveling uphill or downhill on a particular road or trail, showing the steepness, slope, and elevation of the area through topography lines.
How to read a topographic map
A topographic map shows elevation and landforms shapes, while also helping to determine soil type, ground conditions, and stability. Here’s how to read one to get this information.
Reading contour lines
Elevations on a topographic map are marked with contour lines (also called topography lines), which connect points of equal elevation. Imagine walking around a mountain in a circle, never going uphill and never going downhill but staying at the same altitude. If you traced the path you walked, you would have a contour line on a map.
Topography lines are typically separated by 40 vertical feet, though you should check the map you're using to be sure, and every fifth contour line is usually marked with an actual elevation.
Determining land features
The shape of the topography lines can tell you the shape of the landforms in a particular area. For example, concentric circles show a peak, with the smallest circle marking the summit. Contour lines that are close together indicate that the land is very steep, while contour lines that are spread apart show that the land is relatively flat.
Why is topography important?
Reading a topographic map doesn’t just help you understand elevation and landforms. It can help you to deduce the soil type, ground conditions, and stability of any area by looking at those elevations and landforms. Where does all that rain go? It doesn't just stay up on that mountain top. How does that effect the soil below? All of these details make up the topographical picture of the land on which we build our homes and businesses.
As such, from a site planning perspective, topography helps to determine whether a property is suitable for a particular type of building and where the best place for the structure to go is.
How to find the topography of a site
There are a few different ways and combinations you can use to find the topography of a site, including:
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Topographic maps: As we mentioned above, topographic maps give great insight into a given terrain and can help determine the type and quality of the soil.
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Aerial photography: High resolution aerial photographs and satellite imagery will show the topography of a site from above.
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GPS surveys: This isn’t a DIY approach because you need specialist equipment but this technique involves using GPS receivers to determine precise locations and elevations, and then representing those either on a map or digital elevation model (DEM)
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Mobile mapping systems: Again, this is more of a professional technique. It involves mountain mobile mapping systems onto a vehicle or drone to capture data while moving through the site. An accurate 3D models of the terrain can then be developed.
Of course, the other options is to hire site plan designers who will include the topography of the site.
How we use topography in your site plan
Did you know that the U.S. Geological Survey began surveying land in 1879 to create commercially accessible topographic maps? There are more than 54,000 in existence. We at MySitePlan use the information from these maps to add contour lines in two to five-foot intervals on your custom site plan.
Notice the topography lines in this image? The lines that are closer together indicate a steeper elevation and the lines farther apart indicate a wider plain.
So, the next time you step onto the road less traveled, you may start to see those rolling hills, valleys, and streams a bit differently and understand how every elevation and even the soil might affect your next building project.
| Question | Answer |
|---|---|
| What are the common scales used in topographic maps, and how do they affect the level of detail visible? | Topographic maps come in various scales, commonly ranging from 1:10,000 to 1:250,000. Smaller scales cover larger areas with less detail, while larger scales provide detailed information about smaller areas, ideal for detailed planning. |
| How can topographic maps be used in disaster management? | Topographic maps provide crucial information on elevation and landforms for assessing areas at risk of natural disasters. They are used to plan evacuation routes and safe zones. |
| What is the importance of contour intervals in understanding a topographic map? | Contour intervals, the elevation difference between lines, are key in understanding the terrain's steepness or flatness. Smaller intervals indicate detailed elevation changes, essential for precise terrain analysis. |
| Can topographic maps be used for underground planning, like subway systems or utilities? | Yes, topographic maps assist in underground planning by providing surface elevation profiles, helping to determine the depth for placing utilities or subway systems and identifying potential construction challenges. |
| How does the accuracy of a topographic map impact its use in urban planning? | Accurate topographic maps are crucial for reliable urban planning decisions regarding land use, infrastructure development, and environmental protection, highlighting the need for precise and updated maps. |
This article was originally published on 2018-09-26 by Heidi Chandler. This article was updated on 2024-04-30 by Ryan Crownhold to reflect updated information.
