I don't like his method of measuring the curvature distance.
I think it will be very difficult to align a local to the local tangent of the earth's surface. Over a distance of 700m, the earth's surface deviates by about 4cm. This means we would have to align our laser to within 50 microradians in order to accurately measure the deviation of the earth's surface.
Further more, his two beam system is setup using two lasers spaced about 4m apart requires even greater accuracy. Let's imagine system 1 is aligned to the local tangent at one end of the terminal (x = 0m), system 2 is aligned to the local tangent 4 m away at x = 4m, and heights of the two beams are measured at the opposite end of the terminal (x = 700 m). The height difference between these two beams will be about 1 micron. If we assume that the beams are large enough that there is no spread in beam size, then each beam is about 3 cm in diameter. This means we need to measure the beam height to better 0.003% accuracy relative to the beam size. I think this will be a very difficult measurement.
I think there is a way you could very accurately measure the relative angle between two beams in a larger interferometer and two lasers, but I'll have to think about how it would look...
Regardless, it's always fun to think about this small corrections to our expectations. To be honest, I was a little surprised to think about it, 4cm of deviation over 700m is actually a bit larger than I expected.
Your approach mirrors what mine would have been. If the curvature of the earth can be measured over 725 meters, then to me, it's inconsequential whether or not that is detectable within this man-made construct.
That isn't to impugn the question, or the method, but that I'm less interested in whether the architects adjusted each each to be 4cm higher than they would need to be or not. Even if the airport were built over the course of 5 meters, in which the curvature would be (effectively) undetectable, the airport itself, being man-made, may exhibit irregularities caused by human error, shifting ground, variable bedrock, etc.
Regardless, the article was fantastically fun to read, as was your post.
You don't need to align anything: Point a single laser down the hallway and measure the height of the beam above the floor at the ends and at the midpoint. If the hallway is straight, these will fit a line; if the hallway is level, they will not. You can surely measure the heights to an accuracy much better than 4cm, and that's all that matters.
Could you imagine Boeing/lockheed/GM/some some oil company or any other manufacturer going up to their stockholders and saying: "This next year, profits will be significantly reduced as we replace every piece of equipment we own, replace every 1/4-20 screw with an M5, and redesign every aircraft/automobile/widget to meet new metric specifications"
I suppose it'd be better than being Boeing and going in front of your stockholders to explain why your marketshare is radically down because you refused to conform to the measurement system 95% of your customers are using.
It's a non-question anyway. Boeing planes already report fuel load in litres. Funnily enough, flight levels are internationally represented in feet (well, 100-feet) so there's a "win" for you. Also, ground speed is measured in knots!
The knot isn't quite as arbitrary as most imperial measures.
1 knot = 1 nautical mile/hour
1 nautical mile ~= the distance travelled by someone at the equator in one minute due to the Earth's rotation
Since navigation at sea was strongly dependent on the position of the sun and stars, it makes sense to use a unit of speed that makes your calculations easier.
Even for modern navigation it makes sense to use a unit of measurement based on the circumference of the great circle surrounding the Earth.
Boeing has run into occasional problems by holding to imperial rather than moving to metric and these will only get worse, esp. with their model of using vendors around the globe. In aerospace it's ugly since imperial is so entrenched, but other industries have retooled, there are examples to learn from for efficient transitions.
GM already went metric.
Lockheed destroyed a half-billon dollar space mission by clinging to imperial.
Aerospace is the origin of the insanity which is modern pipe thread specifications. The metric version is still in inches, but whatever 1/8" means, the pipe it goes in no obvious dimension represents that size.
Like, I know there is a system and calculations behind it, but they are in no way friendly to any user.
There are costs to sticking with the imperial system. Non-US buyers want metric products which fit with their existing tooling. The factories of the world want all-metric manufacturing, which reduces costs. Error from unit conversion is a real problem.
Designing new products in metric wouldn't require old products to be replaced with imperial. Each product line has it's own special repair kit, spare parts, already. It's not like the suppliers who actually make parts aren't equipped to do metric if they're selling parts worldwide.
The UK went metric in the 1960s and it managed just fine, so there's no reason why it can't be done. Some pragmatism can be involved, for example road signs in the UK are still in miles, and one can still buy a pint of milk or beer (though the latter are technically labelled and sold in millilitres).
A move to metric wouldn't dictate the internal practices of a company like Lockheed, they could still require their suppliers to build parts in inches (even if that means that formally they purchase 2.6234cm sized screws or similar) and they can continue to do everything in inches. Not that they'd want to.
Ireland also went metric. We switched road speed limits in 2006ish, so all the signs say "km/hr" so you don't forget (it's also helpful to tell when you cross the border unto hr uk). Beer is sold in 568ml (1 pint), but milk is sold in litres.
It's quite interesting in Australia that you buy a pint of beer if it's in a glass (or a pot, which is much smaller or schooner, pronounced 'skooner', which is a bit smaller), but bottles are never sold as imperial are generally 375mL.
In England cans of cider are 500 mL. Honestly I don't really think a pint is a unit (except for old people buying milk?), it's a descriptor like "a glass" or "a pitcher" that just happens to have a legally required size. I have an idea roughly how much a pint is but I wouldn't requisition three pints of hydrofluoric acid.
Could you imagine Boeing/lockheed/GM/some some oil company or any other manufacturer going up to their stockholders and saying: "We're going to avoid the metric that most parts are manufactured in (economies of scale) and most of our outsourcing partners are familiar with (risk of errors) and instead stick to customary measures because a foot feels 'more natural'"
It's not like the metric system was invented yesterday and will vanish tommorrow. Change doesn't have to be instantaneous, it can be gradual over the years (and, as the article pointed out, already is)
I agree that things won't change instantaneously, but I also don't think change will happen or even could happen as quickly as most of the talk on the internet thinks it should.
These articles make the rounds on the internet every few months, which gives the impression change should happen quickly. But, given the enormous costs that exist to switch over, I think it's more likely we'll see a gradual change over our lifetime.
Also, switching to metric units for measurement doesn't mean you have to switch the physical size of parts: there is nothing in the metric system requiring that you use round numbers in manufacturing. Canadian engineering, for a mixture of historical reasons and ties to the U.S., measures in metric but often has parts with suspicious sizes like 101.6mm.
I did a bit of work at NASA a couple years back, they wanted everything in millimeters (possibly to deal with the aftermath of that incident). Everything. Even antenna lengths.
I work in manufacturing, and one thing I've noticed here in the U.S. is that metric hardware (nuts, bolts, etc.) is consistently more expensive than comparable-sized imperial hardware. I've never received a satisfactory explanation why.
I have a similar issue using Brighthouse in Florida. For the longest time I was able to stream HD quality from netflix through my roku, until recently. I always suspect that my ISP is somehow the cause, the only problem is I can't imagine how I would prove it, or what I could do even if I could prove it.
So I understand that on of the main points of contention is that the paris cab drivers face steep regulation in the form of requiring an expensive license, while the Uber drivers require no such license, and that to counter this lack of regulation they require the Uber drivers to wait 15minutes before picking up their customer.
But there are still a few things I don't understand:
Why do the Paris cab drivers require such regulations?
How come the Uber drivers aren't required to have such a license?
And maybe I don't completely understand the advantages of Uber (because I've never used a cab before), but at first glance, it seems the main reason uber is succeeding so well, is that there is an app to quickly summon a driver. So why doesn't such an app exist to call these licensed drivers who are so angry?
Taxis are regulated in most countries, typically in exchange for a fee and following a set of regulation they'll get the exclusive right to pick up people on the street.
The precise regulations vary but generally the type of things they include are:
* Criminal background check
* Level of city knowledge
* State of car
* Prohibited to refuse to pick someone up
* Prohibited to refuse short journeys
* Regulated pricing
* Rules on detours
Most of those regulations don't work anymore though, being a cab driver in 2014 with the GPS and all the technology is not the same as it used to be. In paris I take the taxi mostly to go to the airport (it's too expensive for anything else) and most drivers have to use their GPS to get me there. I would expect a taxi driver to know how to get to the airport from Paris.
I'm not generally against regulation but being french and living in paris I cannot really defend the cab drivers. Riding a cab in Paris is pretty expensive and the drivers are often rude (even by french standards). Many of them try to "scam" you anyway by pretending that their card machine is broken so you have to pay cash or others. If you read french you can find a bunch of testimonies here[1]. The title is "why I don't want to take the taxi anymore".
That being said while I'm in favour of deregulation those people have paid upwards of 200 000 euros for their licenses so I understand that they fight for the status quo.
I wish they would fight by improving their services instead of harassing people though. I wonder how this'll turn out. Maybe the state can reimburse the cost of their licenses? That would seem fair but I really doubt the government would do that in the current economic situation...
I can certify that taxi drivers in Paris casually refuse more than half their rides, based on skin color alone — and openly confess that to anyone, no need to ask — and they have committed enough road infraction in any sitting to loose their driving license for good.
I generally use taxis when I'm late for a plane, so the only thing I could do was call:
- Police department say they see issues frequently, but clients are often foreigners, and unable to testify;
- the head office, G7 (because they need to be named and shamed) reaction was that hiring and paying road criminals was not their concern. After making that phone call several times, I support long prison sentences for the executives of that company.
I'd argue that a system that tests on practical taxi driving, such as London's Knowledge would be a much more useful way of vetting taxi drivers than Paris' system of limiting it to whoever can pay a quarter million euros for a medallion.
The problem with cabs is when they are circulating looking for work. They are causing congestion for no real benefit. Regulation caps how much useless congestion there is by capping the number of cabs on the road.
Limo companies don't cause this unneeded congestion because they only go out when they have a job to do, so there is no need to regulate the number of limos on the street. Whether or not Uber should be regulated depends on what their drivers do with their down time. Do they trawl the streets or do they get off of them? It seems like they should get off the road since they can't really pick people up without a reservation. However they may trawl good spots for pickups like near bars or something in which case they are causing unneeded traffic and should be regulated.
most limo services (don't know about uber) offer fixed rates (time or distance). Since Taxis pick you up and start running a taximeter to charge you, that's something that needs to be regulated to make sure that they don't stiff you. If a limo service shows you the route and gives you a quote on the cost, then there would be no need for that level of regulation as well.
There are some regulations that should be there in common, such as protections for the passenger (since you're effectively imprisoned) but stuff like background checks should suffice and I'm pretty sure that Uber and the other companies do this.
That makes sense. So i guess from the perspective of the regulators the options are now either prevent the uber cabs from being flagged down from the street to remove the incentive to roam the street and keep the limo/cab markets separate and ensure the streets remain clearish. Or, remove the regulations, find some way to appease the old cabbies (refund the large license fee), and hope the lack of regulation does not cause huge traffic problems (maybe ticket loitering or cruising, as done in some small towns).
Paris has an incredibly strong Taxi union, which has enjoyed it's monopoly for many decades. Uber cars not being unionized means they are taking money from this massive institution. I think, quite simply, it's cronyism.
Also, the 15 minute wait is because the taxis-by-dispatch are inherently slower. Instead of trying to compete, the taxi union pushed hard on Paris and got them to pass the restriction.
Generally, rather than innovating and trying to compete, the taxi companies in the union have taken the much simpler route of attempting to blockade the upstart.
Agreed. The taxi situation in Paris has been a pain in the ass for a long time. Ever try to get a taxi to go to the train station or airport on a busy day? Sometimes you can't get one b/c of the artificially low number of taxis in Paris. Each successive government in France tries to do something about the taxi unions and fails. Uber will succeed hopefully. http://online.wsj.com/news/articles/SB1000142412788732455780...
>Also, the 15 minute wait is because the taxis-by-dispatch are inherently slower. Instead of trying to compete, the taxi union pushed hard on Paris and got them to pass the restriction.
Two months ago when Dallas' incumbent Taxi monopoly tried to pressure the assistant city manager into regulating Uber out of the market a 30 minute forced delay was a tactic they tried push through as well (among a few others like using the Dallas Police vice dept. to gin up phoney stings).
Luckily the community rallied, Uber drivers got to continue operating, which everyone but the incumbent viewed as fair since the Uber drivers were already licensed limo operators and the incumbent had some insurance problems exposed when the local reporters picked up the story.
I cant speak directly for Paris, but in my home town, one reason we limit the number of taxi cabs is because we've decided (as a society regulating itself) that too many cabs is a social problem. It may sound funny, but imagine a case where there is a lineup of 200 cabs clogging the airport to get that one lucrative fare. Alternatively, outside of a office building to aim for CEOs. They take up a common good that is free (space and to some extent air quality) and therefore are a tragedy of the commons case.
Have you experienced "too many cabs"? How do you know the "social problems" aren't just imagined? How do you know they cannot be controlled in other ways?
You imagine "200 cabs clogging the airport" -- have you seen how cabs work in places where they are plentiful? There's no point in having 200 at an airport at once. They don't take passengers at random, they line up and wait their turn.
If there are a lot of cabs at an airport, the drivers will be better off going into the city and finding a fare there than waiting in a line of 200 cabs.
If there is actually such demand that 200 would "clog" the airport at once, they're obviously solving a problem that isn't being solved by alternative means, such as cheaper and more efficient busses and trains.
Why would drivers aim for CEOs? Cab fares are regulated, so that just leaves tips (something not even customary in many places). They'll get more in a couple hours driving around than waiting for the lottery in the form of an abnormally generous CEO.
This is a good point. In most cities, cabs do not go to the airport unless they have to.
It just isn't a good use of their time - if you drive all the way out there with an empty cab, you've just sunk a whole lot of gas and time on a deadhead when you could have spent the same on picking up several fares downtown. And even when you have someone who wants a ride out to the airport, it's not necessarily something you want to do because then for a return fare you've got to go to the cab stand and take whoever you get wherever they want to go - which could be somewhere way out in the weeds so you still end up stuck with a dead head. That's the reason why in most cities there are actual laws on the books saying cab drivers aren't allowed to refuse to take you to the airport - without those laws, many of them would.
Maybe the specifics of my town are different, it costs ~$60 to go from my house to the airport, thats really good money for 40 minutes / 25kms. Maybe 60 minutes of spent time? (20 minutes to get to me + 40 minutes to get to airport). Expenses on a car are < 50c a km. So $12.50 in auto expenses + $47.50 for 1 hr work.
I never said it was the smartest answer to the solution, merely gave the "reason" behind the politics. W/o the regulation to line up, maybe they wouldnt?
You've made lots of statements about how things would work, which I doubt you could back up w/ evidence.
The 2005 article is irrelevant to any point I've been making, and the 2001 article is both ancient and matches not at all my actual experience living in Taipei this decade. Both are from a source with all the integrity of Fox News.
I can't speak for Paris either, but when I was in Accra in Ghana around 10 years ago I found their approach to taxis fascinating. I don't know their regulations for them but they seem to be effectively unregulated.
In that city what seemed like every 10th car or so is a taxi, it'll take you no more than 30 seconds at almost any given point in the taxi to hail a cab. By social convention the cab will stop for you even if it already has passengers, if the passengers are going to a similar location they'll ad-hoc split the fee.
It was cheap enough due to the unregulated nature that you could take a cab for all your trips, and there was almost no incentive to have a car in the city. The number of cars overall was probably drastically reduced, and it was a much more efficient system than any similarly sized metro bus or tram system I've been to in a similarly sized city.
I don't know what the ideal system is, but consider the tragedy of the commons you might be imposing by artificially driving up the price of what might effectively become small ad-hoc point-to-point public transportation in lieu of personal vehicles for everyone, or a larger and less efficient public transportation system.
It seems like if anything resembling a normal, competitive market experienced the situation of "too many cabs" it would self correct quickly as the rates for individual drivers would plummet. Sitting in a line of 200 cabs for one paltry fare would not be a viable way to operate a cab.
Most of those 200 cabs would soon disappear, because a cabbie cannot keep cabbing if he/she doesn't get fares.
I wouldn't be surprised if some folks that own taxi companies in your city lobbied the council-people with that social good argument, as a means to maintain an artificial scarcity and keep cab prices up.
I think a more likely explanation would be incumbents in the cab industry not wanting to see the value of their taxi medallions (for cab companies) or driver permits (for cab drivers) getting diluted. They both stand to maximize their profits if by limiting their competition. And at least for cab drivers, it's not too hard sympathize with them on that front.
But Uber does solve some real problems with traditional taxi service. In many cases it does a better job at solving the problems that might historically have been addressed by just having more cabs, such as it being difficult to get a ride at certain places/times. To that end it would be nice if more cities would allow regular taxi drivers and cab companies to get in on something like UberTAXI so that it can be a better solution for them as well.
I believe it's more likely that the reason is that scarce resources have a higher value/price.
The society regulating itself (read: taxi unions and politicians) recognizes that if the number of taxis weren't limited, the prices of the fare would go down, usually favouring people which are desperate enough to earn some money (read either young or immigrant). This would drastically reduce the wage of the non-immigrant french/american/italian citizen who has to provide for it's own family.
If the regulation would impose a minimum fare (in order to disallow competition among taxi drivers), there are still concerns that individual taxi drivers would have a bad time competing with taxi companies (with drivers that don't own the car or license).
The licenses are limited in number, and re-sold. They’re seen by taxi drivers as a kind of life insurance. Talk about abolishing them or issuing more and, you guessed it, they’ll strike.
This is why regulation is more often bad than good. It always starts out with great intentions and often works well in the beginning, then crumbles over time either do to it's own bureaucracy, it's selective enforcement, or it's crippling effect on technology or markets.
In addition, it's always difficult to evolve the law with the times, or remove it entirely, than to create new ones. So we're left with an ever-growing legacy of non-productive policy.
In general market regulations start out with good intentions, but the protection they afford specific groups eventually tends to seen as a sacred right by those groups. Especially after the first generation--those who could still remember a time without that regulation--have passed on.
The type of regulations that can work well are those that benefit a large number of diverse groups (i.e. financial regulations preventing banks from doing stupid things with their customers' money) whose interests are so poorly correlated that they cannot effectively organize for a monopoly on some special privelege.
You would think we would be swimming in discussions of the history of, say, the New York City medallion system. But the only thing I can find are links to a book that I may have to read, Graham Hodges’ Taxi! A social history of the New York City cab driver, and vague references to the Great Depression and strike violence.
"The competition 'was merciless,' according to Hodges, and 'Many cabbies turned to petty crime to help make ends meet.'
"There were strikes, and there were fare wars.
"Ultimately, an alderman named Lew Haas decided to do something about it.
"In 1937, he proposed a bill that would limit the number of taxis to 13,595, and make medallions automatically renewable, tradeable assets. It was signed that year by Mayor Fiorello LaGuardia."[1]
"A 1934 strike turned violent, despite various promises of taxi drivers' associations to Mayor Fiorello LaGuardia that peace would prevail."[2]
"Until 1935, the taxi industry in New York was comprised of unregulated companies fighting for dominance. This all changed during the Great Depression. Widespread poverty prompted many New Yorkers to opt for less-expensive forms of transportation, decreasing the demand for taxis. This put many companies out of business and caused many cabdrivers to lose their jobs. The situation was made worse by the tactics of 'wildcat' (unlicensed) taxis who used what some considered to be 'underhanded tactics,' such as drastically lowering fares, to get more business."[3]
Paris, where the meter starts when you call the cab. After the second time with 40+ Euros on the meter we stopped calling cabs and flagged one on the street. Third trip we figured out walking was faster.
So, I don't understand. Why does bitcoin have such high deflation?
Is this just because there has been a constant stream of people switching their traditional currencies for bitcoins at a rate faster than bitcoins can be mined?
Presumably at some point bitcoin will stop being deflationary if it ever wants to be useful as a currency. When does that happen?
Why do people buy bitcoins if it isn't really useful as a currency yet? I mean, there are supposedly 3.5 billion USD worth of bitcoins in existence, but if I want to buy any sort of physical product or pay for utilities, I have to use a traditional currency.
Currently it appears that bitcoins are most popularly used for less than legal purposes (payment for drugs, payment for services to avoid taxes, payment for blackhat services). Does this mean that by buying into bitcoin, I'm essentially providing USD to these black market activities which might not have had USD to begin with?
Even more unreasonable: His original reason for wanting the list of zipcodes was to correlate the zip codes of some health inspections in some county in Oregon to a specific location. Undoubtedly, these health inspections are older than one day, and therefore using two year old data from the census would probably provide the same accuracy as the zipcodes updated daily.
I feel like this legislature would be a huge cost to startups wishing to do business in Germany, and would likewise be a huge cost to already established businesses.
Of course, I suppose there is the added benefit that many companies would now be legally required to have a physical presence in Germany, requiring the creation of many more local data centers. Presumably this would boost the already high performing German economy.
I wonder how this would effect IRC servers. Would you have to forbid connections from Germany if there already was a user connected from Germany?
In that same line of questioning, wow would a teleconference work? Two german companies and two american companies are communicating in a group call via skype or something. The server is located in the US. Does this mean that the two German companies are communicating with each other and therefore the server must be located in Germany? If the US had the same laws, does this mean it is impossible for the group call to be made at all?
How much more difficult would it make telecommuting if multiple telecommuters are located within Germany?
What if user A located in germany wants to send an email or instant message to user B in germany, but is VPNed to a server in another country. Maybe User A is on a business trip to germnay and is VPNed to their work, or something. How could such a message be routed completely within the German borders? Would the VPN have to detect the nature of the message and reject it?
I don't think that you are understanding it correctly. First it helps to understand some history. In the ancient voice telecoms networks of the 20th century there was the principle that "he who dials the number pays the bill". Therefore, when a telecom provider (like DT) tried to connect a call with another telecom provider (such as BT in the UK), both telecoms companies knew that there was money flowing into DT's pockets. So the recipient's provider (in this case BT) wanted some of that money. This became a principle worldwide that interconnects between two networks had to be bought and paid for. Of course, calls went both directions over the interconnect so the concept of peering was born. What it meant was that the two companies would count up the calls at the end of the month, and the one with the most calls would pay the other company.
Then came US telecom deregulation, CLECS, the growth of the American-centric Internet, and a new way of making connections. On the Internet, one party opens a socket and superficially that seems to be similar to dialling a phone call. But the big difference is the the party opening a socket is not paying anyone a fee to do this. And they aren't paying a per-minute fee for using the socket. In fact, the party opening the socket is paying money for the use of the whole network, and the party whose socket is being opened is also paying a fee for the whole socket. Thust the concept was born that interconnects should be free because they are a cost of doing business as an ISP.
And then began much confusion and strange business dealings as telecom management wrestled with how to reconcile these two worlds. The result was that deregulated US providers charged a lot less for interconnects, and the international telephone calls of the world started to take a detour through the USA. And internet connections did the same thing.
So basically, there should be no extra cost if Germany implements this. Some companies might get into arm-twisting battles if significant traffic flows shift from one circuit to another because they will likely need to upgrade some interconnects, but that is just a one time hit. It should not increase fees at all.
I don't understand, should the SEC only occaisionally enforce the laws? Would you prefer a situation where he was not prosecuted for insider trading, even though this is a crime he committed?
Are you suggesting that the SEC successfully enforces insider trading laws?
The SEC catches maybe 0.01% of insider trading. The inherent difficulty in enforcing insider trading has led many policy makers to push for legalizing the practice.
The more cogent question is, in light of recent revelations, why did they investigate this particular case instead of all the other potential cases?
Could he even tell them that he knew that the government contracts would fall because he refused to comply with the government? Would that be insider knowledge of something?
So they were going to crush his business and he tried to cash out? I don't know the whole story, but it seems that this is one of those cases where the SEC chose to occasionally enforce the law....
Would it be illegal for the companies that complied as they may have known that cooperating with the government would earn them lucrative contracts that their companies could benefit from?
It just doesn't seem right. Everyone else gets retroactive immunity and Nacchio goes to jail.
I would be fine with consistency. The SEC should not charge this man, or charge him and every person who is aware of any non-public government contract and trades in the sector the contract pertains to. Within reason, of course. Like, executives of all firms with (prospective or realized) government contracts, any time they buy or sell the stocks of their own firms, or grant themselves equity. Do we have any reason to believe that the law is enforced in this manner in general, or is it more likely that this is not the case, and it was enforced in an unusual manner in this particular instance?
The real question is why the SEC scrutinized him in particular. They do not have the resources needed to scrutinize everyone or catch everyone who engages in insider trading.
If I understand both you and the parent correctly, you are describing the same process. When you melt two fibers together, the cores aren't really becoming one. Really, they melt together such that light from one core partially evanescently couples into the core of the adjacent fiber.
So the question becomes, to how young a person does this apply? How far back can be extrapolated? Is a slow 40something as meaningful a data point as a slow 70something year old?
I think it will be very difficult to align a local to the local tangent of the earth's surface. Over a distance of 700m, the earth's surface deviates by about 4cm. This means we would have to align our laser to within 50 microradians in order to accurately measure the deviation of the earth's surface.
Further more, his two beam system is setup using two lasers spaced about 4m apart requires even greater accuracy. Let's imagine system 1 is aligned to the local tangent at one end of the terminal (x = 0m), system 2 is aligned to the local tangent 4 m away at x = 4m, and heights of the two beams are measured at the opposite end of the terminal (x = 700 m). The height difference between these two beams will be about 1 micron. If we assume that the beams are large enough that there is no spread in beam size, then each beam is about 3 cm in diameter. This means we need to measure the beam height to better 0.003% accuracy relative to the beam size. I think this will be a very difficult measurement.
I think there is a way you could very accurately measure the relative angle between two beams in a larger interferometer and two lasers, but I'll have to think about how it would look...
Regardless, it's always fun to think about this small corrections to our expectations. To be honest, I was a little surprised to think about it, 4cm of deviation over 700m is actually a bit larger than I expected.