Point of Beginning

Tech Talk: When is Surveying Considered Mapping

December 2, 2011

It never fails--when I conduct a seminar and ask “who’s a surveyor?” most hands go up. Then I ask “how many of you do mapping?” and very few hands go up, maybe 2 percent to 5 percent of the room. To me, these responses demonstrate the lack of vision or breadth in the opinion that many surveyors possess about their work and their profession.

While some will call it heresy, I consider mapping to be the spectrum of technical and professional activities within which surveying falls. If you use my description, then surveying is part of mapping, albeit a highly specialized part of mapping. A similar analogy is that physicists, chemists, zoologists and botanists all fall under the term “scientist.”

But the title of this column is “When is surveying considered mapping?” I would not say that all of the time this is the case--but much of the time this is true. So what is surveying? It is the measurement of the relationship between points, lines, planes and volumes on or near the Earth’s surface. If we wanted to generalize, we could take it beyond the Earth into the whole universe, of course. And what is mapping? Without resorting to a dictionary, I would say that it is the physical and (today even more so) digital representation of the relationships between points, lines, planes and volumes on the Earth’s surface. Many would say this is the work of the cartographer, but how many surveyors do we know who do the measurement part and then turn their work over to a cartographer?

If you read about historical events--be it the expedition of Lewis and Clark, the work of the General Land Office (GLO) surveyors in the early 19th century, the journeys of Magellan or Col. Claude Birdseye of Grand Canyon fame--these people were called surveyors, geographers, explorers, mapmakers and even topographic engineers. It seems that people from centuries ago understood better how these now separate professions (and sometimes simply labels) had to be integrated if the results of their work were to have any meaning at all.

But back to “what is mapping?” Some of you may recall from way back in high school algebra that there is another kind of “mapping.” In algebra, we learn about mapping the elements in one set to another set. In an abstract way, that is what surveyors do. They take discrete points that exist in the set of the real world and find ways to map them in the set of the two- (sometimes three-) dimensional map so that the relationships between those many points are correctly represented and in a way that the map reader can understand them. Does a surveyor who does not make maps still get called a surveyor? Without answering the question, I don’t know what type of surveyor that would be. Whether property boundary, engineering, construction, geological, mining, hydrographic, topographic, control or geodetic or whatever type of surveying one purports to specialize in, the fact of the matter is that one of the products of a surveyor’s work is one or more types of maps. He or she needs to be an expert at taking measurement data to construct maps, analyze the contents of maps and extract useful information that is not readily apparent to the layperson by sometimes using more graphic means (maps?) to summarize or report on surveying work.

Of course, sometimes surveyors are specifically hired to make maps: hydrographic, topographic, planimetric, etc. Surveyors even know how to construct maps that don’t show the normal physical features, such as mountains and valleys. These can be contour maps of the Earth’s gravity or magnetic field; pollution levels; strength of radio signals (from space- or land-based transmitters); nontraditional physical attributes, such as the varying thickness of a large concrete pad; the depth of the water table or ice in a glacier; average wind strength and direction; and even the status of projects.

Surveyors are not cartographers, the experts at making maps. But they certainly do make maps as a byproduct of their work or specifically because their clients request them. Surveyors who want to cast off the title of mapper are doing so out of a lack of understanding of what mapping is or because they have misinformation. One of the most common misunderstandings is that mappers are not as precise as surveyors. It is true that surveyors do make a lot of measurements that are reduced to a map that may have been measured with more precision, but that is often simply an issue of scale. And a mapper who is used to making gross measurements because the activity is the map of a country or county or 1,000 blocks would know to either make more precise measurements if the consumer of the mapping data required it, or if the mapper didn’t know how, a surveyor would be hired with the expertise to get the required precision. I’m not sure, however, if the accuracy mappers strive for is necessarily less than that what surveyors strive for. If you think of accuracy as the nearness to the absolute truth, the fact is that surveyors tend to be much better at precise relative measurements than accurate absolute measurements.

Yes, a professional can claim to be a mapper and not be a surveyor. A surveyor may claim to not be a mapper, but the truth is that both use skill sets that the other has. For me, being a mapper is part of being a surveyor. And for those who thought I was going to take a different tack in this column, you should know that I’m proud to have written it without a single mention of GIS.