Topographic survey: why your architect or engineer needs one

A topographic survey maps the shape of the ground and everything on it: slopes, high and low points, trees, buildings, driveways, utilities. It is the base drawing your architect, civil engineer or builder works from.

What it shows

• Contour lines and spot elevations, tied to a reference datum or a local benchmark;
• existing buildings, walls, pavement, fences and other improvements;
• trees above a chosen size, often with species and trunk diameter when a tree ordinance applies;
• visible utilities (manholes, poles, meters, valves) and drainage features (ditches, culverts, swales);
• often the property lines, when the topographic survey is combined with a boundary survey.

When it is needed

• Designing a new house, an addition or an ADU, especially on a sloped lot.
• Planning a driveway, a retaining wall, a pool or the grading of a yard.
• Solving drainage problems: water against the house, a wet yard, runoff to or from a neighbor.
• Many site plans and grading permits require it, and so do septic designs on some lots.

How to brief the surveyor

1. Tell them who will use the survey (architect, engineer, builder) and ask that person for the exact list of what they need.
2. Say how far beyond the work area to survey, for example the street, the neighbor's driveway or the nearest storm drain.
3. Ask whether the boundary should be included: a topographic survey alone does not establish property lines.
4. Ask for the file format your designer needs (PDF, CAD file) and the datum to use.

Describe your project in the form: licensed surveyors near you get back to you with a written quote for your topographic survey.