U.S. Survey Foot vs. International Foot Standard
Many in the surveying and geospatial professions are aware of a proposal by National Institute of Standards and Technology (NIST) to “deprecate the U.S. survey foot” as a unit of measure. This action would have the effect of declaring the “international foot” as “the standard foot” when it comes to the measurement of land and all things relative to it. This is an issue of significant concern to professional surveyors and all geospatial practitioners in the United States.
The discussion thus far has raised some strong emotions. However, having strong emotion – in fact, passion – regarding a subject does not dictate that clear and objective thinking regarding that subject is unachievable.
As a professional surveyor for more than thirty-five years it has been my training, my understanding, and my experience that we have a sacred duty to the public interest. Those words are not chosen casually nor for rhetorical effect. I hold that they are fact. Please reflect on that for a moment. We are one of very few disciplines where duty to the public must come first – before self and before the client. There are a number of compelling reasons that this is so, not the least of which is that it is impossible, by definition, to establish the boundary (or limit) of anything without simultaneously declaring the boundary of its adjoiner. Hence, when determining the location of a boundary I must consider the effects on that adjoiner and, likewise, the effects upon the community. A professional land surveyor cannot merely mark some geometry upon the ground as if he or she was independent of the surroundings. That is why we are a learned and licensed profession.
This isn’t “just a surveyor thing.” It affects everyone touched by geospatial issues in the United States – which is everyone. Now is the time for our profession to step forward on behalf of the people of the United States. No one who has practiced very long in the geospatial arena, least of all a professional surveyor, is unaware that the vast majority of the public has very little understanding of the principles and realities of this work. That is our responsibility. This is just the kind of thing where professional surveyors may employ their primary skills, knowledge, and professional experience to great effect. In the paragraphs that follow, I make the case that implementing the international foot as the United States law of the land is contrary to the public good. However, don’t take my word for it. Do what we are charged to do:
- Gather and discern reliable, appropriate, and adequate evidence.
- Evaluate that evidence in the clear and objective light of the appropriate context and governing rules.
- Render a professional judgment in accord with our duty.
I believe when you have done that fully, your views will fundamentally align with those presented here. Not because of strong feelings; not because of inertia or tradition; not because you abhor change or you harken to the “good old days;” not because it will be easier or more profitable for you; but because upon mature consideration and after exercising due diligence you have reached an informed and well-reasoned conclusion and you have acted to serve the public interest first and foremost.
New Standard Datum
In 2022, a new modernized National Datum will be implemented by the National Geodetic Survey. This is a necessary and beneficial thing. Riding on the coattails of that advance is a proposal that we should use this as an opportunity to redefine the foot. The proposal seeks to establish the “international foot” (IF) as “The foot.”
The two issues are separate. The new datum – which is based upon the meter – does not in any way depend upon the existence of the IF. The premise is that the U.S. Survey Foot (USSF) is somehow now superseded, and the potential for using the wrong unit causes confusion. The potential does exist, mostly causing a problem for geospatial professionals. However, it is the recent introduction of the international foot into a well-established province of measurement – that is, the three-plus centuries of land and public works development of the United States – that has caused the problem.
The IF proposal so fundamentally misunderstands the purpose and nature of geospatial measurement it is difficult to believe that it could even be taken seriously let alone be championed by someone who holds himself out as an expert. The goal of the proposal is to declare that there is only one foot and that is the recently developed international foot. That simply is not the case.
This is not about “deprecating” a unit of measure. It is about implementing a different unit under nominally the same name as the old and presuming that it will not cause problems.
This issue was grappled with and resolved twice already. The conditions that persuaded our predecessors of the better course of action are only clearer now. They judged well and left us worthy footprints to follow in.
Below I make the following points:
- The proposal causes the very problem it purports to solve.
- There is no real benefit, and there is significant, real, current, and long-term cost in changing to the IF.
- The problems it causes will affect millions of properties, more than a billion acres worth many trillions of dollars, and create confusion for geospatial practitioners and their clients.
- Implementing the use of the IF for U.S. geographic measurement does not serve the public interest.
- The IF is not a better unit for geographic purposes. It is merely a different, and, in this case, inappropriate, one.
- Resolving this problem once and for all can be done by declaring that the correct foot to use for U.S. geospatial practice is the U.S. Survey Foot, which could also be reckoned the U.S. Geographic foot.
Introducing Problems Where None Exist
In practice, we use all sorts of units: chains, varas, arpents, meters. What’s the problem?
The primary issue is one of confusion. There is little problem of confusion between information in feet versus in meters – because the disparity is obvious. Both the unit identifier and the difference in scale naturally lead to rapid clarification. It is a fundamental principle of all geospatial practice that to conduct meaningful analysis the information must share a common spatial reference system. The basis of that system, no matter what it is, includes a defined distance unit. Problems ensue when the wrong units are used. The wrong units are used when very similar but disparate units are mistaken one for the other. When we introduce a “new foot” into a well-regulated established body of geospatial information and ask all users forevermore to sort out the differences, what can be the result except confusion?
Those of us who work in the realm where there is only one foot – the U.S. Survey Foot – don’t have this problem. We either work in feet or meters. It is simple, known, effective. It doesn’t matter when the work was done because there is only one foot.
Proposing that adoption of the IF is going to solve a problem demonstrates the same flawed reasoning that contends “just put GPS coordinates on everything and we won’t have any problems with measurements” or that “the problem is not with distances it’s just about the coordinates” as if coordinates can exist without distances. If you are not competent enough to check and validate the operation of your equipment, procedures, or software to the point of knowing what unit you are working in, how much faith should anyone have in your ability and commitment to correctly interpret myriad potential points of discrepancy that are not uniform or labeled as are the settings in your software, instrument, or data collector?
All competent professionals are adept at using appropriate units, whatever they are. Professional surveyors are accustomed to dealing with dozens of discrete units, many of them very local or esoteric.
The point of confusion is not one of different units existing; it is one of indefinite or confused units being used in a particular context. The latter condition is solely and directly a result of the application of an inappropriate unit. This is exactly what the introduction of the IF into the geospatial realm has caused.
Use of the IF Provides No Actual Benefit
What benefit does using the IF for geospatial purposes provide to the citizenry or geospatial professionals?
- Is it more accurate? No.
- Is it more precise? No.
- Is it more “exact” than the USSF? No.
- Does it provide any efficiencies of measurement, calculation, or use? No.
- We live in a global society and it is called “international” so that must be better, right? No.
South America does not need the international foot to measure its geography. They employ the meter, as does Africa, Asia, Europe, Canada, Australia, and, in fact, our own National Geodetic Survey. If required, any of these jurisdictions may render distances in a local unit. For example, although there are many different local values for the vara, there is no need for an international vara.
In short, the IF does not provide any real benefit in the geospatial realm.
The IF is not a better unit; it is just a different unit. For geospatial purposes in the United States, the IF has no place. It does not solve any existing problem. It only provides unlimited opportunities to spawn the problem of confusion.
In the geospatial realm, our commerce is not with merchants and mechanics in other countries. It is with the physical environment both built and natural and with the measurements (within the same geography) of our predecessors and contemporaries. We don’t need to worry about mismatch between our bolts and the nuts made in Britain. We need to concern ourselves with the location of utilities mapped in our county ten or twenty years ago or with the control monumentation documented in our state a half-century ago.
The introduction of a new unit does not change yesterday. To paraphrase the esteemed Justice Cooley, our job is to establish measures not as we would do but as they were. Is it possible to coordinate measurements using any unit of distance we like? Of course it is. My instruments or software can use any unit I choose – meters, varas, cubits, even the accursed International Foot. Yes, I must be certain of the unit I am working in, but that is an ever-present requirement. It’s part of our competence as a professional licensed surveyor. As long as there is clarity as to the conversion factor between units, there is no problem except potentially the limit of one’s own knowledge and diligence. And that is the crux of the issue. It is folly to attempt to mandate the use of a new unit to interface with the vast trove of information expressed in another unit of a similar name but different constitution. It would be like expecting high precision parts manufactured to the British foot to fit correctly into a machine manufactured to U.S. foot standards.
The Change is Not in the Public Interest
Mandating the use of the IF unit will cause incalculable cost, effort, and trouble for anyone attempting to work with foot units in the U.S. Anyone even casually following the geospatial arena has witnessed the exponential growth, popularity, and utility of geospatial data. That trend is going to continue for many years. There are trillions of pieces of geo-data today, and untold billions more will be generated every year. These data do not exist in isolation, not from each other. What they are isolated from is international exchange. Within the geography, they must inter-relate – across time; across subject. To expect users, however sophisticated, to cope with and account for artificial discrepancies with every usage – discrepancies created by design – is to completely disregard the premise of a spatial system.
Descartes would be spinning in his grave. This is not right reasoning.
The possibility, let alone the certainty, of two nominal but different units means every analysis will need to evaluate every set of geospatial data to see what foot was used. This needs to be done for directions already due to unavoidable differences in the basis of bearings. But, to require it for all foot distances as well is ludicrous. If the IF becomes standard, you will have to explain to all clients and users of your data why it disagrees numerically with the previous information. “Your coordinates aren’t right. It doesn’t line up with my map/data/plans.” The profession and the industry need to be seeking ways to come together and simplify, not to divide and complicate.
A 2015 study by the Bureau of Economic Analysis established the basic values of land in the lower 48 states. This is land and value controlled by surveys and geospatial data that is directly influenced by this issue. The numbers are illuminating. Over $20,000,000,000 worth of land is affected. Mandated adoption of the IF will impose a burden of change and confusion on many more than suffer under it now: almost five times more by area; nine times more by land value; nearly 11 times more by population. This proposed change, in addition to the financial and practical costs, would no doubt cause emotional turmoil among the unknowing public we are duty-bound to protect.
This is something like a horror movie in which the hero shatters an object of evil only to have a new evil sprout from every shard. How much will it cost practitioners to deal with the discrepancy, to protect against potential mistakes when they may now crop up at dozens of new junctures? How much will it cost to resolve claims that are made because of perceived numeric discrepancies in plans or with historical records?
The standard is about measurements that are going to be published; it cannot change what has been. A bell cannot be “un-rung”, and this proposal will not erase the past. It will only create an uncountable number of indefinite points of potential discrepancy – each of which will need to be checked. And someone will need to check them – at a cost. And if we should fail, we will only further the stereotype that “No two surveyors can agree.” Of course, now we will drag the whole burgeoning geospatial community with us.
Before World War II and the widespread exchange of precision goods, machines and parts were being manufactured using different standards in different countries, but they were all named and hence presumed to be the same. The IF was developed and implemented for a purpose – to support international commerce and the reliable interchangeability of goods. Goods such as nuts and bolts and bearings. Things exchanged between countries. It serves that purpose. Geography is a bit different though. It is seldom exchanged. The USSF was adopted and preserved to meet a very different and distinct purpose – to support the reliable interchange of information and value relating to geographic features. The two units operate in different realms. Both are necessary today, but only one in each domain. Eventually, as products wear out and customs change toward the de facto standard of the meter, the benefit of the international foot will go away. Until the land, the records, and the development supported by the USSF wear out there will be need for the unit.
Land and geography are not like nuts and bolts. In the geospatial realm, we deal with records as much as we deal with what will be created. Much, if not most, of what we deal with is effectively permanent, or at least as permanent as the works of humankind can be. Our predecessors wisely foresaw this issue and took a pragmatic course. In 1959 and again in 1983, with the release of the new National Geodetic Datum, the nation and the geospatial community had the opportunity to adopt the IF. They wisely chose (with a few exceptions) to hold the USSF as the proper foot unit. They were not hoodwinked by the siren song of modernity. They understood the nature and practice of their profession.
The U.S. Survey Foot, even if the calumny of “deprecation” is committed, will never “go away” and the sentiment expressed by one zealot to “kill the U.S. foot once and for all” is a fool’s errand.
The Only Foot Value for U.S. Geospatial Information
The USSF is intended for application solely to geographic measurements in the U.S. domain. That is an objective condition that is reasonably determinant and easy to ascertain. Hence, the problem of confusion is inherently limited.
There should be only one foot value for geographic use in the United States, and that value should be the one the country was built upon – the U.S. Survey Foot. The contention is that the USSF is an archaic unit. It is not only as perfectly valid as it ever was, it is near-universal in use within its correct domain, which is U.S. geospatial information.
There are a few actions that could be taken to actually help with the problem intended to be solved by the proposal:
- First, declare the USSF the correct foot for all published U.S. geographic information – whether for land surveys, foot-based plane coordinate systems, or public works. Use the USSF or use the meter, but don’t confuse matters by introducing the IF.
- Second, if there is ongoing fear of incorrect application, brand the USSF as the U.S. Geographic Foot.
- Third, eliminate the use of the foot for geospatial applications and publish data – particularly coordinate systems – only in meters, as the NGS originally intended.
It is a fact that the true standard unit of measurement for the geospatial realm is the meter. Surveyors who dispute that have not checked their prism offset recently, nor do they fully comprehend the operation of total stations or GNSS. The distance unit of modern science is the meter. The IF is merely a pacifier that will undoubtedly die away when its short-lived purpose is served. I think it will be a very long time, however, before we don’t care about the conversion factor between the meter and U.S. Survey Foot. Using the IF when you should have been using the USSF is not an error. It is a blunder, a mistake. And, even those who have only completed their first year in any spatial discipline must know that the primary difference between errors and mistakes is that while errors can only be managed and minimized, blunders can be eliminated. The use of the IF for U.S. geospatial practice is a colossal blunder which we should now work to eliminate.
It is our duty to protect the public from a gross abuse that is about to be perpetrated upon them. They are in no way prepared to even recognize it, but they will pay for it in small incremental unrecognized ways, perhaps or potentially in catastrophic ways, but for many years they will pay the cost. If there were ever a time for our profession to demonstrate its leadership and value to society, it is now.