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Home arrow Archives   The American Surveyor     

The Largest Non-BLM Cadastral Retracement in History Print E-mail
Written by Brian Dalager, LS   
Sunday, 18 July 2010

A 2.204Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

Maricopa County, Arizona, is the 14th largest county of roughly 2,950 counties in the country. It contains roughly 5,904,616 acres within its bounds, over 25 municipalities and communities and more than 3.5 million people who call it home. It is approximately the size of Massachusetts, Rhode Island and Connecticut combined. We surveyed over 14,000 section corners and quarter corners for this project. The Maricopa County Department of Transportation (MCDOT) decided to undertake this project to help in managing the right of way of their projects as well as increase the accuracy of the geodetic fabric of the Geographical Information System (GIS).

The Need
The survey was known as "The Geodetic Densification and Cadastral Survey" or GDACS for short. The project was undertaken for a twofold purpose: 1) to create an accurate and reliable foundation for all GIS's in Maricopa County Government, and 2) to help resolve, clarify and prevent future land boundary issues within Maricopa County.

There is an increasing demand for accessing accurate information, specifically from GISs. GISs are playing a huge role in running cities, counties, utility companies and private firms. Since most of the land boundaries in the western United States, more specifically Maricopa County, are tied to the Public Land (Rectangular) Survey System (PLSS), accurately locating the section corners and quarter corners is a must for land parcel rectification.

A GIS is an avenue for accessing nearly any type of information graphically, making complex data retrieval quickly accessible. Examples range from querying how many trees are on a given parcel to accessing in-depth engineering plans for additional road design. We have already become dependent on GIS and our need for these systems will continue to grow. A key component of any GIS is the foundation on which it is based. This foundation is a layer made up of points that other layers or features depend on for spatial orientation. The accuracy of these points can directly impact the usability of the GIS. The origin of these points have come in many forms in the past, from digitized maps to obtaining miscellaneous land survey information, often from varying and questionable sources. Currently many GIS control layers are in error up to 200 feet. This project has improved the precision and accuracy of the geodetic fabric up to 1,000 times resulting in control point error ellipses within 0.20 feet or less.

Another important goal of the project was monument/corner preservation. Even though Arizona has fairly strict rules on recording plats, we knew that if we could survey endangered section corners and quarter corners it would be doing a service to the surveying community, and thus, the public. Since the establishment of the original surveys in Maricopa County in 1860s through the 1920s, many of these corner monuments have been destroyed or lost only to be replaced oftentimes by several "competing" monuments attempting to represent the original corner. In situations where this has occurred, copious amounts of time and money are spent in attempting to resolve discrepancies in land boundary lines. With this project surveying preserving the original monument positions will hopefully reduce future conflicts.

The Project
The initial project began in August of 1998 and was completed in August of 2005. The following consultants were contracted to perform the work: AMEC Inc., A-Team and Associates, David Evans and Associates, Robert Bein William Frost and Associates, Entranco, and Wood Patel and Associates. There have been several large addendums and subsequent work since then with help from Alpha Engineering. Altogether there were 87 corner determination plats and 42 inventory plats recorded, covering 129 townships. With more than 14,000 monuments surveyed and nearly 9580 section and quarter section corners determined, the work continues to this date.

Control
The first task was to establish a high accuracy survey control point every four miles throughout the county. The Barry Goldwater Military Gunnery Range, Indian Communities and the Tonto National Forest were excluded from this coverage. This network enables any private or public land surveying activity to be rectified to one common coordinate system. Before the project began, there were only seven "B" order or above, nationally recognized control points in the county. Choosing new locations where we had permission to install, clear of sky obstruction, easily accessible and yet secure enough to leave a GPS receiver were our primary goals. Most of the stations have a forged eyebolt set in concrete to lock a receiver to it if so desired. With the successful completion of this project, there are now 484 new control monuments. The monuments have been added to the Federal database held by the National Geodetic Survey, and are available for public use. The total cost to establish these monuments was $715,298.76 or $1,477.89 per monument.

Even though Continuously Operating Reference Stations (CORS) and Real Time Networks (RTNs) are currently operating in the Phoenix area with more stations proposed in the future, these monuments will continue to serve as control points to those clients that require projects to be completed in the NAD83 1992 datum adjustment, as well as great physical checks to the overall system.

Section Corners and Quarter Corners
The second step was to locate all of the PLSS monuments in areas where development is proposed or currently under way. Proposed, includes areas that MCDOT is anticipating development over the next 20 years. The consultant was required to survey, photograph, physically describe, determine, refurbish, replace (if needed), and record. This was more than simply locating and surveying the monuments. Corner determinations of lost corners were performed by the consultant's, incorporating legal documents, applying boundary principals and procedures, resulting in the best efforts for properly determined corner positions. The results were then gathered, organized and uniformly documented on an officially recorded survey plat. Each plat would cover one township, but some plats span more than one or a partial township. A great deal of time and energy went into formatting the plats so that uniformity among them regardless of survey firm, would yield to create a consistent and easy-to-use product. Each plat contains: 
• A cover page(s) of the overall township boundary with bearing and distances between all accepted corners. 
• A coordinate table with latitude, longitude, ellipsoid height, State Plane coordinates, elevation, convergence angle, combined grid scale factor, last date the monument was visited and a detailed monument description. 
• A township history timeline from inception to current day, detailing when the GLO originally created the township and any resurvey work completed since then. This area also included an index error, the difference in distance between the latest GLO/BLM survey and today. 
• A record table containing all the records used in making corner determinations. 
• A corner determination table containing a detailed explanation of the analysis, methodology and records used to accept the monument as the corner (essentially, the footprints of the signing surveyor).

Consistency
Due to the size of the project, six surveying firms were assembled to complete the project under the management of MCDOT. One of the most complicated tasks throughout the entire project was to create consistency among all the firms. A successful project would not only be one that was accurate, but also seamless in nature, to give the public the appearance that one unified firm produced it. Given the competitive nature and individual style of six different surveying firms, this was not an easy task. The problem was overcome by a strict and articulately thought-out set of specifications that would guide the project from beginning to end--a "book of rules" that all the firms would agree to follow. This 52-page manual, including five appendices and an example plat, explained everything from how to survey a monument to what size fonts to use.

Monument Attributes
Even with the in-depth specifications, keeping field crews entering the physical attributes of the survey monuments proved a challenge. A system was devised by creating a menu-driven application in the field data collectors that prompted the field crew by asking specific question at each monument. This reduced, and nearly eliminated, the chance of forgetting certain attributes and miskeyed information. Once the data was gathered in the field data collectors, a separate program was written to extract the information and generate easy-to-read monument descriptions. The system saved countless hours of hand editing and dramatically increased consistency.

Record Analysis
To properly evaluate each monument for a corner determination, all available survey plats, field notes, previous corner ties and related documents needed to be analyzed. In a typical township, (6 miles by 6 miles) there would be on average 600 records with some townships reaching over 2,000, many with multiple pages. We estimate that approximate 48,000 records (plats) were printed, organized and analyzed. In order to manage not only the volume of records, including the content contained within, spreadsheets were utilized. This proved the most efficient and effective for referencing and analyzing final corner acceptance and/or placement.

Corner Determinations
A key motto of a land surveyor is "Follow in the footsteps of the previous surveyor." This is a fundamental element of successful corner determination. Unfortunately, records seldom explain the thought process that land surveyors went through to reach a conclusion. One of the most innovative features of a recorded GDACS survey plat is that for every corner determined, a detailed explanation of exactly which records were used and why they were used is a part of the final document. When a corner was not found, the determination explains what mathematical process was used to reestablish it and with what records. In doing this, a twofold benefit was realized: 1) All subsequent surveyors using the plat know the thought process of the determining surveyor, and 2) It has dramatically reduced the number of inquiring calls to all the firms.

With over 558 separate deliverables to be submitted, tracking completion and delivery of product became an issue. An innovative procedure was implemented by utilizing the web for delivery tracking. Each of the surveying firms would go online and see which products have been received and accepted by MCDOT and which deliverables were still outstanding.

Data Access
Depending on the format of the data you are requesting, a variety of ways are created to access the data.

If you are looking for the officially recorded plat for a particular area, you could access the Online Plat Index site (http://www.mcdot.maricopa.gov/ SURVEY/). Simply use the pull-down options to direct you to the area in question, and it will build a section list wherein you can choose the plat, view, download and print the plat.

If, on the other hand, you are interested in a more hands-on approach with the data, it has been loaded into an ArcMap Geo-database that is being served through an interactive online map. (http://www.mcdot.maricopa.gov/SURVEY/). This allows users to do the standard zooming in and out to areas of interest, but it also has many other options that are helpful to users: 
• Zoom to intersection with error trapping 
• Zoom via Latitude Longitude 
• Zoom via point number or name 
• Zoom via Township, Range and Section

Once located to your area of interest, you will notice the quick and clean orthophotography that blankets the background. On the map, several options are at your disposal. You can select one point at a time and double click to retrieve the data regarding the point, including positional information and associated photos, or you can window and download a coordinate list. All of these features make it one of the most advanced survey websites available.

Project Cost
Even though change orders were issued on some of the individual sub-phases, the actual cost of the entire project came within 1% of the estimated budget. The original cost estimate for the project was $7,440,000 without the change orders. With the change orders it came to $7,660,000. Not only was the amount unprecedented for a land surveying project, but finishing under budget was quite an accomplishment.

Brian Dalager is a licensed surveyor in Arizona and New Mexico, and also as a CFedS. He works at Maricopa County DOT in Arizona. He is a graduate of California State University Fresno and has been surveying for 15 years.

A 2.204Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

 
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