Total station or RTK DGPS: which does your site need?

A total station measures from the ground

A total station measures angles and distances to locate points relative to an established setup. It is useful for detailed site measurement and setting-out, where the surveyor can establish suitable sight lines. Buildings, walls, equipment and vegetation affect where the instrument can be positioned.

Reference: Leica Geosystems: total station systems

RTK uses satellite positioning and corrections

RTK GNSS uses satellite observations and correction information to calculate positions in real time. “DGPS” is often used more broadly in project enquiries, so confirm the actual method proposed. GNSS observations depend on the surroundings and the available correction service.

Reference: Trimble: RTK initialization and good survey practice

Site conditions shape the choice

Open sky can favour GNSS work. Tall buildings, tree cover and reflected signals can make observations more difficult. Trimble’s guidance recommends clear sky when initializing RTK and checking the initialization through repeat measurements. A total station offers another way to measure detail where suitable ground control and sight lines are available.

Reference: Trimble: RTK initialization and good survey practice

Control connects the measurements

For a combined survey, observations need a consistent coordinate and height reference. Ask how the work will relate to your existing drawing or benchmark and what checks will be made. Instrument specifications alone do not describe the accuracy of a completed site survey. The control, method, conditions and verification all matter.

Specify the output before the equipment

For a quotation, start with the site and intended result: a contour plan, boundary comparison, coordinate schedule, construction set-out or as-built record. Let the surveyor propose the method and explain the checks, achievable requirements and limitations for those conditions.

• What reference system and benchmark will be used?
• Which site conditions affect the proposed method?
• What independent checks are included?
• Which drawings, coordinates or reports will be handed over?