“GIS Mapping and Boundary Surveying; what’s the difference?”
As time marches on, we will see more and more municipalities turning to a very powerful analytical tool called a Geographic Information System (GIS). This tool allows the municipal users to make good, informed decisions concerning the allocation of taxpayer money – for example, to determine where the most effective bus routes should be placed, to spot trends in crime, or how best to use their road maintenance funding.
It is all done by associating the different kinds of data to specific geographic locations within the municipality. The data can then be viewed graphically in a format most people are familiar with - a map. The production of the base map is completed, taking into consideration many different factors; the most prominent factor being the cost. Municipalities, especially at the local level, are always looking for the most economical way to be more efficient, primarily because they must answer to the tax payers. The creation and production of a GIS base map is not immune to this level of scrutiny and so its development is subject to, and defined by the intended uses of the GIS.
For example, if the community gets involved with a GIS project for the intended use of keeping track of maintenance and replacement schedules for their fire hydrants, then to what accuracy does the map need to exhibit? A) ± 10 feet B) ± 3 feet C) less than 1 foot or D) about 1/8th of an inch? There is no wrong answer here because each option will allow the municipality to tell one hydrant from another and therefore, assign the correct replacement/maintenance schedule. The real question is what is the budget for the base map? As I’m sure you can guess, producing a map with an accuracy of ± 10 feet (option A) is much less costly to produce than option B, which is much less costly than option C, which is much, much, much less costly than option D.
In general, municipalities will usually go for option A or B or C since those will work for their intended purposes. Option D is what one might call “Survey Grade mapping” The knowledge, techniques, training and equipment needed to produce this level of accuracy and precision are different than what is needed for the other options and take a great deal more time to accomplish. For a GIS application, it is overkill. For determining a parcel boundary, it is essential.
A popular feature of the municipal GIS is the ability to bring in aerial imagery to lay under the GIS parcel map and data. This is where the trouble starts. Since the municipalities want to give their constituents access to this powerful tool, (remember you the tax payer bought it) they can offer limited access to the GIS through the internet. Usually, after a few clicks, most homeowners can find their parcel and turn on the aerial image behind it.
I can hear it now… “Ooh check it out, there’s our house, there’s our driveway, and there’s the neighbor’s…. hey, why is the neighbor’s garage over the property line!?”
Except that’s not the property line. It simply represents the idea of the property line, not where it exists on the ground. For that, you need a Boundary Survey completed by a licensed professional surveyor. BMJ Engineers & Surveyors have been providing expert advice on parcel boundaries since 1970. Call us today for a free quote and consultation.
