Topographical Survey also known as Elevation Survey is a survey that depicts the contours of the existing grade. Not to be confused with an FEMA Elevation Certificate, this kind of survey is conducted to facilitate construction or used for the hopes of obtaining approval of a developmental project. In addition, the survey map is used for planning and design purposes by an engineer or architect.
Similar to a Boundary Survey, the land surveyor is responsible for locating existing conditions of all visible improvements such as buildings, walls, fences, driveways, etc. in relationship to the original property lines. In addition, the elevation of the existing grade, public utilities (telephone, electric, water, gas, and fiber optic cable lines) that service the area, sewer lines (storm and sanitary) and the inverts are observed and depicted. The product of a Topographic Survey is a Topographic map or sometimes referred to as an elevation map or a site plan. The elevation map shows the existing conditions and features of a parcel of land including spot elevations and contour lines. A spot elevation is a specific point of elevation on the ground or structure shown on a map. Contour lines are curvilinear lines on the topographic map that connects points of equal elevation of a predetermined height. This is a useful tool to determine the slope of the land and its steepness. The inverts are the elevation of the sub-terrain utility pipes that service the property. A topographic map is usually used for design purposes by an architect or civil engineer. A Topographic Survey is usually done in conjunction with a Boundary Survey and might be essential step prior to Construction Layout. The first step in a topographical survey is establishing a “Benchmark”. This benchmark will serve as a control point to establish the horizontal and vertical positioning (elevation). Typically, the benchmark’s coordinates will be determined by using an existing geodetic monument or by measuring the location of the monument complemented with GPS instrumentation. All the field measurements are linked to this benchmark location which allows the surveyor to achieve 3 dimensional coordinates for every observed measurement. Afterwards, all the gathered data is analyzed and converted to a drawing using a CAD program. The topographic map is then delivered electronically to a designer who will then use the map to for their specific needs.