High-accuracy, survey-grade GIS

May 2007 » Feature Articles
Bringing together GPS, land surveying, and GIS technology, offers the ability to have spatial boundary information that simultaneously unifies, integrates, and perpetuates land surveys with sub-centimeter accuracy.
Robert Jones

There is a sea of change taking place in technology that is reshaping how spatial boundary information is interpreted and retraced.

Boundless is coupled with GPS and GIS technology to create a high-accuracy, survey-grade GIS that creates virtual surveys.

Spatial information for land surveying has existed in isolation. However, by bringing together GPS, land surveying, and GIS technology, there is now the ability to have spatial boundary information that simultaneously unifies, integrates, and perpetuates land surveys with sub-centimeter accuracy.

National Survey & Engineering, a division of R.A. Smith & Associates, Brookfield, Wis., has developed Boundless, a patent-pending, high-accuracy, survey-grade GIS software that uses value-added code written for ESRI’s ArcMap. A web-based version is in development that uses ESRI’s ArcGIS Server 9.2 platform.

Boundless bridges the gulf between land surveying and high-accuracy GIS. Regardless of location, it is now possible to integrate unaltered survey drawings and their databases as they currently exist. In its web version, Boundless collapses the walls of spatial isolation, as high-accuracy spatial data can be integrated into a GIS that can be accessed via the Internet, regardless of what organization originates the data.

How it works
Boundless accesses multiple drawing databases while simultaneously accessing associated Earth Centered Reference Frame (ECRF) databases. Spatial data is extracted from the databases, and Boundless integrates otherwise unconnected surveys within a selected area onto a common map projection—on the fly—with insignificant distortion. For the first time, unaltered survey drawings and their databases as they currently exist worldwide can be integrated spatially. Thus, surveys and engineering projects, regardless of who created them, can be integrated within a global GIS with access via the Internet.

Boundless works within any coordinate system. It’s a software program that uses point and line information by accessing multiple selected survey drawing files and point databases. At the same time, it accesses Global Navigation Satellite System (GNSS) data that are associated to the drawing databases via project number and location. It then transforms the information into a unified coordinate system. Importantly, there is no distortion that alters scale or geometry as established by engineering plans and as measured on the ground per legal description. The result spatially relates previously unrelated land surveys.

Features
Spatial data can be collected, stored, integrated, and managed via Boundless. The following are significant features of Boundless:

  • Most surveys exist in isolation from one another; Boundless unifies surveys by spatially relating them with survey-grade accuracy.
  • Issues with disparate coordinate systems are eliminated.
  • Boundless surveys are tied to the International Terrestrial Reference Frame.
  • Using high-accuracy GPS, surveys reflect grid as ground measurement.
  • As a GIS, Boundless can associate other data to the survey via the GIS database.
  • Surveys are perpetual once stored in Boundless, creating no future reliance on physical markers.
  • Boundless operates seamlessly between the GPS, survey, and GIS technologies, requiring no changes to existing survey or GIS operations.
  • Surveys can be grandfathered into Boundless.

Survey markers that have been destroyed or removed is a common problem. Boundless creates virtual and perpetual surveys, eliminating reliance upon physical markers such as iron pipes.

In regard to the feature mentioned above about reliance on physical markers, for engineering firms and land surveyors in particular, this is a common problem in finding and re-establishing site control. Frequently, surveyors travel to a site only to find that the iron pipes, concrete monuments, crosses in sidewalks, or other physical markers are long lost.

It is not only land surveyors who are impacted; public officials, attorneys, developers, utilities, title companies, real estate professionals, and others struggle with the complexity of a national land system that is hundreds of years old and often presents challenges.

Upon surveying a property via high-accuracy GPS and through Boundless, a surveyor revisiting the site can navigate to a specific point using GPS.

Surveyors rely upon search and find methods to locate physical markers. Boundless stores survey data for relocating a point with sub-centimeter accuracy without relying upon a physical marker.

During construction, when physical markers are disturbed or destroyed easily, re-locating a point can be done via navigation back to the missing point, not by search and find. But the benefit goes beyond time savings and efficiency; there is a practical aspect of safety. Sending crews out into high-traffic highways or hazardous areas is minimized.

More on coordinate systems
A key element to Boundless’ effectiveness is the National Geodetic Survey’s national coordinate system, the National Spatial Reference System (NSRS). The NSRS determines position, height, distance, gravity, and shoreline throughout the United States. Currently, property is measured on the ground by surveyors to determine property lines and their relationship with improvements. Boundless requires the same procedure; however, there is an important distinction—the measurements use high-accuracy GPS, tying the survey data to the NSRS.

Instead of relying exclusively on physical monumentation, surveys are memorialized via Boundless using the NSRS. GNSS, Continuously Operating Reference Stations, and Virtual Reference Systems are three significant components that allow surveyors to link existing survey drawing databases to ECRFs. And the result is sub-centimeter accuracy.

The analysis, comparison, and understanding of land boundaries or legal descriptions between adjoining properties are simplified, regardless if the survey data is collected in different projects or not referenced to the same coordinate systems or monuments. With the potential power of virtual survey information within fingertip reach, collection, storage, and management of spatial information is being freed from the constraints of physical markers and individual, spatially unrelated databases. Boundless is a stake in the ground for the new digital age of land surveying.

Robert Jones is a survey project manager with National Survey & Engineering, a division of R.A. Smith & Associates, Inc., headquartered in Brookfield, Wis. He can be reached via e-mail at robert.jones@nsae.com.


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