Don't trust the internet for boundary information
Gisborne Herald Article by Paul Ericson, Registered Professional and Licensed Cadastral Surveyor and Principal of Grant & Cooke Surveyors Ltd – Published 6 September 2016
Major surveying headaches arise from using online boundary overlays.
USING boundary information from the internet is increasing and not reliable, a Gisborne surveyor has said. Paul Ericson, a registered and licensed cadastral surveyor and principal with Grant and Cooke Surveyors Ltd, said there are major problems with using boundary overlays from the internet such as Google Earth and council websites.
“With the ease of obtaining digital boundary information these days, we are increasingly seeing a reliance on the information provided as if it is reliable and can be taken as verbatim,” he said.
“Nothing could be further from the truth.”
Mr Ericson said there are four major problems with boundary overlays.
One of them is that aerial photos are invariably not taken vertically above the subject, so there is rarely an accurate depiction of building versus boundary.
Another problem is that aerial photos are commonly not rectified, which means the scale varies depending on the topography, and boundaries are not locked on to the ground correctly. “Google Earth is a good example of where boundaries can be moved ‘at will’ to make things supposedly fit,” Mr Ericson said.
Another issue is that the boundary information is supplied by Land Information NZ.
WARNING: Gisborne surveyor Paul Ericson says people are taking boundary information provided on internet sites such as Google Earth and council websites as verbatim. “Nothing could be further from the truth.”
National digital database
“When the cadastre (database of boundaries) was shifted from manual storage locally to a national digital database, the complex network of boundary lines was sourced by scanning hand drawn record sheets.
“At a scale of 1:50,000 (which these commonly were in rural areas), an error of 1mm amounted to 50m on the ground. In bigger cities, where development has been fairly robust, these anomalies have been ironed out by modern surveys providing accurate up-to-date information.
WHY NOT TO USE THE INTERNET TO SURVEY: Here is an example of how using boundary overlays from the internet such as Google Earth and council websites can cause problems. This image shows the boundary line of a property using information from a website.
The actual boundary line, surveyed by a registered surveyor. It shows that the boundary line goes straight through the house.
“In regional areas like Gisborne, where progress has been slow, one can never take this information for gospel. As an example, some rural areas can be 50 metres to 100 metres out of position,” Mr Ericson said.
The fourth main issue is that every legal survey carried out by a licensed cadastral surveyor has to consider many factors including researching certificates of title, old survey plans and documentation, and any other relevant information. The internet-based options do not.
Mr Ericson said it might come as surprise to most people but the licensed cadastral surveyor gathers the documentary evidence and makes the scientific measurements, but his or her decision is distinctly legal, not scientific in nature.
“So there is no one position that can be identified as the true boundary position until the licensed cadastral surveyor has considered all the evidence.
“We are increasingly being asked to give someone the coordinates for their boundary so that they can find the boundaries on their GPS or phone.
“By law, no one other than a licensed cadastral surveyor can define boundaries,” Mr Ericson said.