A contour survey is a detailed map of your block's surface, showing its levels and the natural and man-made features on it. It drives the design, siting and cost of your new home, so it pays to know how to read one.
Here's how to read a survey plan and a contour survey, using a real example.
Lot on Plan: What RP and SP Mean
Before any contour survey, the surveyor needs to know exactly which piece of land they're surveying and where its legal boundaries are. In Queensland, that comes from the lot on plan description.
C2 - Before Site Start Checklist
$59.00 AUD
Last updated 28 Oct 2026 · Revision 3 · Free updates for life
Checklist Type: Minor
Form Factor: Fillable, print-ready PDF (A4, 22 pages)
When to use: Pre-construction (after contract, before the builder starts)
A 70-point site readiness checklist. Find access, approval, level, service, tree and retaining issues before work begins, so you can plan time and cost before the builder starts.
Lot on plan description
Every block in Queensland is identified by its lot number and the plan it sits on, for example "Lot 695 on SP123456". The plan type tells you its age: RP means Registered Plan (older plans) and SP means Survey Plan (the type used for newer plans). The lot on plan description is the unique identifier for your property, so there's no doubt about which land is being surveyed. You'll find it on your title and land contract.
What does the plan show?
The registered plan, drawn by a licensed surveyor, shows the legal boundaries of each lot with precise measurements and bearings. It's what defines where your land starts and stops.
Why the Plan Is Needed Before a Contour Survey
- Establishing Legal Boundaries: The plan defines the boundaries, so the contour survey maps the right area.
- Accurate Reference Points: The plan ties into permanent survey marks (PSMs) and other reference points, which give a baseline for the level measurements.
- Avoiding Disputes: Surveying to the legally defined boundaries avoids arguments with neighbours later.
- Integration with Other Plans: Working from the registered plan lets the contour survey line up with the site plan, engineering and other documents for the property.
What is a Contour Survey?
A contour survey (also called a detail and level survey, or topographic survey) maps the levels and shape of the land. Architects, engineers and builders use it to design the house to suit the site.
Key Elements of a Contour Survey
- Contours: These are lines on the map that connect points of equal elevation. The spacing between contour lines indicates the steepness of the slope; closely spaced lines show steep slopes, while widely spaced lines indicate gentle slopes.
- Reduced Levels (RL): Heights measured from a fixed reference point, usually the Australian Height Datum (AHD), which is roughly mean sea level. RLs tell you how high each point on the block is.
- Ground Level and Natural Ground Level (NGL): Ground level refers to the current surface level of the site. NGL is the undisturbed natural surface of the land before any construction or excavation.
- Cut and Fill Lines: Where the land will be excavated (cut) and where material will be placed (fill) to create a level building platform. Note these are designed from the survey and appear on the builder's site plan, not on the contour survey itself.
- Batters: The sloped faces created by cutting or filling. They hold the soil in place and limit erosion. Like cut and fill, they're shown on the builder's site plan.
- North Arrow/Compass: This shows the orientation of the survey plan, helping you understand the directions and how the site is aligned.
- Overland Flow Potential: This indicates areas where water might flow across the land during heavy rain, which is crucial for planning drainage and preventing water logging.
- Services Locations: These are the positions of existing utilities such as water, sewer, electricity, and gas lines. Knowing these locations helps avoid damaging them during construction.
- Survey Pegs: These are markers placed on the ground to indicate key points measured during the survey. They help in accurately transferring the survey data to the construction site.
Site Photos
Your surveyor will usually photograph the site before surveying it. Here's an example of what you'll receive.
Interpreting the Legend
The legend on a contour survey provides explanations for the various symbols and abbreviations used. Here are some common items:
- O/H Light: Overhead light.
- S/Water Pit: Stormwater pit.
- Fire Hydrant: Indicates the location of a fire hydrant.
- Water Valve: Location of a water control valve.
- Mountable Kerb: A kerb that vehicles can drive over.
- Non-Mount Kerb: A kerb that vehicles cannot drive over.
- Ref R.L.: Reference reduced level.
- Datum: The reference point from which elevations are measured.
- PSM Marks: Permanent Survey Marks used for consistent reference points.
Scale of the Contour Plan
Contour plans are usually drawn at 1:200, meaning 1 unit on the plan equals 200 units on the ground. That's enough detail to see the site clearly while still fitting on a standard A3 sheet.
Easements and Flood Levels
- Easements: Legal rights to use a portion of the land for specific purposes, such as utility lines or drainage. Building on easements is usually restricted.
- Flood Levels: Indications of potential flood zones based on historical data and predictions. This information is vital for designing flood-resistant structures.
How to Read the Plan
To effectively read a contour plan, follow these steps:
- Orient Yourself: Use the north arrow to align the plan with the actual site.
- Identify Key Features: Look for contour lines, RLs, easements, and other critical elements.
- Understand Elevations: Pay attention to the contour intervals and reduced levels to grasp the land's elevation changes.
- Check for Services: Locate all utility lines and services to avoid issues during construction.
- Look at the Cut and Fill: Once the house is located from the boundary setbacks, work out the difference between the platform level and the natural ground level at the base of the cut and at the toe of the batter. That tells you whether you'll need retaining walls, or what landscaping will be needed to hold the platform in place.
- Review the Legend: Familiarise yourself with the symbols and abbreviations used on the plan.
Importance of a Contour Survey
A contour survey is indispensable for:
- Accurate Design: Ensuring the design fits the land's topography.
- Proper Drainage: Planning for adequate drainage to prevent water issues.
- Cost Estimation: Determining the amount of cut and fill required, impacting construction costs.
- Regulatory Compliance: Meeting council requirements and obtaining necessary approvals.
- Locating and Siting the House: Placing the house where it meets estate and council setbacks from boundaries, easements and other features.
Keep this guide handy when you review your contour survey, and ask your surveyor or builder about anything that doesn't make sense.
Soil Test and Compaction Certificate
Below is a typical soil test and compaction certificate you may receive from your developer. They matter because the soil test sets your site classification under AS 2870 (A, S, M, H1, H2, E or P), which decides how heavy your slab and footings need to be. The compaction certificate (Level 1 inspection and testing under AS 3798) confirms any fill on your lot was placed and compacted under engineering supervision. Without it, the fill is treated as uncontrolled and your slab design gets more expensive.
Compaction Certificate
Soil test
Soil test bore setout. We tell our engineer where we want the bores drilled, based on the house footprint and its setbacks from the boundaries. Ideally the bores are spread out, at the front and back of the house. For more, see our guide to geotechnical soil tests below.
Note this is for a different site not Lot 695
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