Conversion Is Out, Measurement Is In - Are We Beginning the Surveying and Mapping Era of GIS?

Many people are questioning the applicability and coverage of state regulatory statutes on surveying and mapping. Could it be that legislature really believes that unlicensed "surveying and mapping of land, water, and space presents a significant threat to the public?" (1997 Florida Statues). At issue is whether new activities in GIS and GPS fall under regulation. Most statutory definitions clearly cover professional services involving specialized knowledge of mathematics, science and the legal requirements for the determination of the facts of size, shape, topography, orientation and legal or geodetic location of features on or near the Earth's surface. Statutes usually state that no person shall practice surveying and mapping unless such a person is licensed. Many questions emerge. What is surveying? Is cartography a branch of surveying? Is GIS activity a form of surveying? Perhaps some answers can be found in a brief review of GIS in relation to traditional surveying activities.

 

The Conversion Era

Most agree that cartography is not surveying because new original measurements of ground features are not needed for cartographic operations. Early developers of GIS, coming from academic environments in geography, used cartographic conversion techniques to build computerized spatial models of features on or near the Earth's surface. Conversion activities were encountered quite frequently from 1985 to about 1995, as a large wave of initial GIS implementations occurred. However, the use of conversion as a primary source to support GIS development is beginning to diminish.

The term "conversion" implies that pre-existing graphical maps are converted from an analog (graphic) to a digital form by such cartographic processes as digitizing or scanning, often with supplementary processes such as differential scaling or warping. GIS conversion has proceeded so rapidly that today, most pre-existing useable maps with geographic accuracy have been digitized. Many USGS quadrangle maps are now available as vector or raster files. County appraisal property ownership maps have become seamless parcel base maps. Utility schematics are presented in overlays over parcel maps. Soil maps are also in overlay files. Contour maps are known as DEMs and are often used in the production of orthophoto base layers for GIS applications.

GIS's Silent Partners

Surveyors and photogrammetrists were "silent partners" in this first (conversion) phase of GIS building. Although their role has never been fully acknowledged, surveying products have formed the basis for geographic fidelity in a GIS. It can be safely said that "all spatial truth in any map can be traced back to a surveying and/or mapping process." Someone, at some time, measured features using a surveying and/or mapping technology—tape, transit, level, theodolite, electronic distance measuring system, aerial camera or satellite positioning system—in order for a map to adequately convey facts of size, shape or location.

For example, geographic accuracy in "tax maps" can be traced to the accuracy by which original surveyors mapped the first divisions of public land within the United States during the 1600s, 1700s and 1800s. Additional accuracy comes from surveyors who furnished measured or computed information for deed calls and recorded plats. When these fragments of information are assembled into seamless ownership maps, the surveyor and mapper's work forms the fundamental basis of accuracy, or ground truth, even though the surveyor and mapper's identity does not carry through the deed writing and map compilation process in most cases.

The concept also applies to USGS quadrangle sheets. From 1920 to 1990, surveyors and mappers for USGS compiled original graphic overlays for quad sheets from field surveys by plane table or photogrammetry, using control sets by geodetic surveyors. Baselines of road and railroad systems were painstakingly calculated, laid out and documented by surveyors and mappers of various road departments or railroad companies. Other surveyors and mappers assisted the power, water and telephone utility companies in developing truth in their utility maps. Photogrammetrists over the past four decades painstakingly contoured the Earth's surface, producing broad contour coverage locally and through USGS quad sheets. Accuracy in georeferenced images can be traced to the source measurement of latitude and longitude of selected control points and, in the conversion process, the scanner or digitizer geometric.

Digital conversion did not increase geographic accuracy of the pre-existing maps. In fact, many times, good map information was degraded by poor digitizing or by georeferencing to approximate control points, thereby introducing stretching and warping that yielded less geographic accuracy after conversion than the map had before.

The Measurement Era

Direct measurement is becoming an increasingly important GIS tool. The only way to develop or enhance geographic accuracy of GIS in the coming years is by direct measurement of features. The problem is that direct measurement of many features on or near the ground is called surveying. Those who perform surveying are called surveyors or some similar title in most states or jurisdictions worldwide.

GPS is the latest in a series of surveying and mapping tools, having come along during the time period when conversion opportunities in GIS were winding down. Those who did GIS by conversion for 10 or 15 years, without direct involvement of a surveyor, naturally expected to move into the realm of direct measurement using GPS under the label "GIS Mapping." However, many state boards of registration are questioning this move, recognizing that the activity represented by GIS mapping includes activities already defined as surveying and mapping in most state laws.

Signs are plentiful that the GIS world is moving toward direct GPS measurement. In many academic, government and consulting arenas today, the terms GIS and GPS are often used together, as in "my GIS/GPS academic course," or "GIS/GPS activity in agency programs," or "a new integrated GIS/GPS." Jack Dangermond, founder and President of ESRI, Inc., announced in 1997 that Arc/Info is extending its data model from the x,y coordinate to those measurements from which coordinates are derived: distances, angles and GPS vectors (Arc News, Vol. 20, No. 1, 1998). Academic geography departments are responding by adding an increasing amount of measurement technology study into a discipline traditionally based in the arts and general sciences, to form new science degrees in geographic technologies.

A New Wave of Surveying and Mapping

Is it possible that we are seeing the emergence of a new wave of participants in the surveying and mapping arena? GIS mappers who began using simple cartographic processes are now migrating toward the traditional knowledge and practices of surveyors and mappers. The term "survey" is of French origin, with the common prefix "sur" indicating "above," and the suffix "vey" meaning "to see," that is, to see as if from above (E. R. Kiely, Surveying Instruments: Their History and Classroom Use. Bureau of Publications, Teachers College, Columbia University, New York, 1947). The term originally applied to activities related to the measurement of earth features and presentation of the land's content graphically in a view from above. Content included spatial relationships, counts, land cover classifications, values and many other position-related facts about things on the land.

The "first wave" of participants in the discipline could be termed "traditional surveyors," those who used compasses, theodolites, tapes, and EDMs to measure and map features by direct measurement. Beginning in ancient times, surveyors can track a continuous record of intellectual development resulting in a well-identified collection of knowledge, tools, methods, applications, books, publications, regulation features and academic programs. Today, there are approximately 50,000 "first wave" practitioners of surveying in the United States.

The "second wave" of practitioners in this discipline is comprised of photogrammetrists and remote sensors—those who measure and map from photos and images. With pioneer work in the 1920s, photogrammetry grew during World War II and has been our dominant topographic mapping technology for four decades. From the early space ages of the 1960s, the field of remote sensing has led to techniques known as "image mapping." Photo and image mappers have developed a professional identity quite separate from surveyors, but with a parallel record of intellectual development, books, tools and methods. Only now are legislatures beginning to realize that all those who measure and map the land should be treated equally from a state regulation standpoint, and photogrammetry is being merged with surveying licensing processes in a number of jurisdictions.

GIS technologists can easily be viewed as comprising a new "third wave" in the surveying and mapping field. The information component is really nothing new. Maps have always conveyed two types of information—spatial and attribute. Map symbols and legends can be viewed as early data dictionaries. New job titles have evolved in the third wave: GIS analyst, GIS technician, GIS mapper, digitizer and so forth. Those performing similar duties in the United States today probably number 15,000 or more.

Distinctions Within the Term "GIS"

The term "GIS" means something different to different professions. To one person (perhaps a surveyor/mapper), GIS refers to the data collection or building process, as in "building a GIS." To another (perhaps a geographer or planner), the term means "spatial analysis using GIS." Yet to another (perhaps a computer specialist), GIS is a "networked computer system serving up maps and data to users." In the earliest days of GIS when the focus was generally project based, one person likely did all of these activities in order to develop and implement a functional GIS. Today, the mere size of the GIS enterprise is calling for shared responsibilities, with surveyors and mappers concentrating on the building process, geographers and planners using GIS analytical tools to analyze and answer queries, and computer specialists serving up maps and data in a reliable and secure fashion.

Outlook for Regulation

State regulation is based on the concept of protecting innocent users who may rely on measured data without being able to judge its quality or judge whether the intended application is appropriate. In the early decades of GIS, the GIS professional was both the "builder" and the "analyst" (or user). Because the data builder is always the most aware data user, the public had limited exposure to geometric accuracy problems and was protected by the wise use and reporting by the GIS builder/analyst. Most historic GIS developments were for the support of projects and studies of limited term. The public usually did not have direct access to GIS data for independent application by persons unknown to the GIS professional, or for unforeseen applications.

Today, the main emphasis in GIS has moved from the "GIS project" stage to a perpetual, multipurpose "GIS program" focus. Many city and county jurisdictions have undertaken large GIS program efforts so that data can be placed on many users' desktops through wide area networks or through the Internet (Thrall and Ruiz. "A History of Implementing an Urban GIS. I: Design, Tribulations, and Failure." Geo Info Systems, July 1994). The GIS professional is no longer the primary user. GIS data must now be made suitable for unknown users who may attempt to make an entirely inappropriate application.

As GIS continues to make its way into the mainstream of society, innocent use will lead to claims of damage, and GIS mapping organizations will modify the data presented to minimize risk exposure. As an example, USGS has already decided to drop the Public Land Survey layer as a maintained layer in the national mapping program in response to several high-profile damage-related incidents that pointed to a misuse of that layer as an ownership base map. Responsibility for that layer is being transferred to the Bureau of Land Management, the agency that is the true source for the data.

GIS organizations will most likely provide additional protection by enhancing GIS personnel credentials, so that GIS organizations will be able to respond appropriately to technical issues that surround public accusations of harm. One of those credentials may be state licensure. Truth-in-labeling, the current quality control paradigm of GIS, may not be enough. Only a GIS professional can make a proper interpretation of metadata. Metadata in itself will not stop an innocent user from making a misapplication of geospatial data because that user cannot really be expected to understand the underlying quality of the data being presented. Instead, GIS data presented for general public use in the future may be required to be tested and certified as meeting some minimum geometric quality standard. Persons doing the certification will most likely hold a state license to do so.

Regulation of GIS activities has been a non-issue until recently. Most state surveying statutes regulate those who make maps resulting from direct measurement of earth features. Therefore, cartographic techniques used by early GIS have been largely exempt from regulation. Cartography deals with issues of effective communication through arrangement of map displays but usually does not include direct measurement of features. For example, most statutes would exempt a geographer who georeferences digitized maps using USGS digital base data because original direct measurements are not being made. Other exempted activities could be newspaper or regional mapping, business geographics, thematic mapping, parcel mapping in assessor's offices, combination of GIS layers into new maps, extracting vector coverages from georeferenced images and making uncontrolled photo enlargements. However, GPS has recently complicated the application of the direct measurement vs. cartography distinction. GPS is definitely a direct measurement technology, and legislatures will have difficulty separating GPS activities from activities covered under existing surveying regulations.

The GIS community should see that licensed surveying practitioners bring many valuable assets to the table—including a long history of operating in the light of public scrutiny, expertise in quality control of measurement and mapping and universal statutory recognition that mapmakers can lie and damage the public. As public reliance on GIS brings more relevance to the health and welfare of the public, inevitable pressures will demand quality control for public protection. Surveying statutes, although they can be interpreted in narrow application today, may be the best available vehicles for ultimate statutory recognition of GIS professionals. Therefore, we should not be too quick to discount the surveyor's present and historical role, nor minimize the value that surveying licensure brings to the development of a professional image for GIS.


 

David Gibson is Director of the University of Florida Geomatics Program, College of Engineering. He is founding chair and governor's appointee to Florida's Base Mapping Advisory Committee and charter member of Florida's Geographic Information Board.

Reprinted with permission from Surveying and Land Information Systems, vol. 59, no.1. Copyright 1999 American Congress on Surveying and Mapping.

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