Hanlons surveyors install control points along railway lines, highways and subdivisions and connect these points to the NSW geodetic network. 

The Intergovernmental Committee for Survey and Mapping sets the standard for Control Surveys. Hanlons surveys are usually to third order accuracy whilst state networks are executed at first order level. The state network is the primary network and itself is connected to the national and international network. 

Most survey undertaken for or on behalf on the public or are registered in a public data base are required to connect to the state network. The NSW Surveying and Spatial Regulation also requires permanent control marks in subdivisions. These are coordinated and the values entered into the NSW Survey Control Management System. Surveyors can access the information for free.

Prior to the widespread use of globall navigation satellite systems (GNSS) such as the USA's GPS, Russian GLONASS or European Galileo system, surveyors connected their surveys to trigonometric pillars using theodelites and laser distance instruments. Trig Stations are white concrete pillars mounted with a black vane for each of sighting from a distance. A great deal of work went into their construction and to determine accurate coordinates. Now surveyors simply pull out their GNSS and spent only a few moments determining a state coordinate position and elevation.

Why is this important?

For a number of reasons. 

Control stations are the "coat-hanger" on which all information is reference to. 

Asset managers such as local councils, railway track managers and highway authorities use the connections to bring the spatial data points for the asset into their spatial management systems. Maintenance programs use these systems to better manage the life cycle of public assets.

Emergency services also use the spatial data during bushfire and flood events.

Lately, autonomous self-driving vehicles will need this information to assist with navigation. Whilst these vehicles will have radar and other on-board sensors, they will also access spatial data that is reference to the vehicle's GPS navigation system. 

It is the relentless drive for productivity that is forcing our spatial systems to adopt higher levels of accuracy of our roads, our property boundaries and our railways. 

So the next time you look at your smart phone and check your location, ask yourself how accurately is it. Also ask yourself if the map picture is in the right place.