Mapcode – A short address for any location on Earth(mapcode.com) |
Mapcode – A short address for any location on Earth(mapcode.com) |
Mapcodes are a free, open way to make every house or location on Earth
addressable by a short code. With nothing else except your mapcode,
for instance, a navigation system will bring someone to within meters
of your front door.
I do know that in belgium they point to an area, so they're not as good as a navigation aid.
Living in the UK, I don't see what this offers over my postcode, which identifies my location to within a couple of houses. The houses across the street have a different postcode to me as do my neighbours three doors away. Theoretically* all anyone needs to find me is my house number and postcode. Try it. Send me a postcard:
madra 84A <----- house no. M15 6FD <----- postcode England
*Actually, it's not theoretical. I have as an experiment in the past sent someone a letter addressed just to their house number and postcode and it got there. In spite of that I do tend to write out fuller addresses though. It just seems a bit too 'minimalist' relying on only the postcode.
Converting longitude and latitude to some other character base, like someone suggested would be better.
Open Street Map is, sadly, no better, thinking my house is a different neighbor's house.
As a rule, address data in OSM is very incomplete and the Nominatim instance on osm.org falls back to things like TIGER data to do geocoding. If you are in a region where there are a lot of addresses present in the OSM data, it would be great if you could at least drop a note nearby stating that the addresses in the area have problems (it's the button shaped like a cartoon word balloon, on the right hand side of the page).
(Housenumbers show up when zoomed in, if they aren't showing, then the OpenStreetMap website is showing you results based on some fallback data.)
But thank you for noting that I can do the same with OSM. After making an account and logging in, I've created a feature-point for my address, but I don't see a way to correct or suppress the incorrect information from OpenStreetMap Nominatim. shrug Problem for another day.
Yeah, but so are the British post codes. 6-7 symbols and you're down to meters usually. At least for the cities. They definitely bring you close to the front doors.
> The mapcode system is a free, open standard.
Which is it, open or patent-encumbered? It can't be both.
> The mapcode system was revived and worked out in 2006 when TomTom decided to expand their operations to countries like India and China. It was difficult to sell navigation devices in these countries, among other things because a significant part of the population lives without address, lacking not just house numbers but often even street names, which often made it hard or even impossible to enter a destination. It was thought that the introduction of a simple and ubiquitous system for representing locations (and hence destinations) would in due time make navigation devices as welcome there as anywhere else.
This one was particularly bad because the submitted title ("Did TomTom founders just kill the postcode?") caused the post to receive a barrage of user flags.
My understanding is that they have acquired building data from many municipalities and will absolutely use that when they have it, not that they have spent a lot of time refining it.
If not, you can leave a note http://www.openstreetmap.org/note/new and someone can take a look at it. I've been contributing for a while now and still like using Notes to let people with more techy experience or local knowledge help.
* Postcodes have a specific meaning: they're both a geographical area and a mail delivery zone (at least in the US). Replacing one short code with another, which requires a different and less reliable third-party service to correctly decode, doesn't seem like a good idea.
* Latitudes and longitudes are unambiguous, well-understood, and don't require a third-party service to be online in order to correctly decode. So it doesn't seem like this can replace latitudes/longitudes, unless we're talking about shortening their representation.
* Broadly speaking, while addresses have a lot of problems, they're unambiguous with human context. So this doesn't seem like it really replace addresses either.
* For things like a loose description that might not be associated with a single point (e.g. "Central Park"), I could see mapcodes being useful -- you can provide the precise boundaries of the park, where it's located, associate metadata with the mapcode like what hours the park is open, etc. That might be very helpful.
Also, won't there be multiple mapcodes for a single spot and won't that require cross-association of the respective metadata? For example, consider that Central Park is also in Manhattan, also part of NYC, also in Midtown in NYC, etc.
I guess that's not necessarily a problem, but it could lead to a lot of expensive processing for frequently updated locations/boundaries (e.g. a beach, a suburban development in progress, etc.).
This is a tangent, but actually, they're not.
There have been (oil) wells fail because someone gave a lat/long without specifying the datum, and someone else assumed it was in a different datum.
Without a datum defined, latitude/longitude (no matter how precise) only gets you to within ~1km of an actual location.
The Earth is not a sphere (or even an ellipsoid). Therefore, we need models of the the absolute shape of "sea level" (i.e. an equipotential surface - varies due to density variations in the Earth) to go from a spherical coordinate system to an actual point on the Earth's surface. These are referred to as a datum.
Because our knowledge of the absolute shape of the Earth has changed over time, there are many different datums (ranging from spheres to ellipsoids to detailed gridded surfaces).
There are a large number of datums that are still in common use. WGS84 is the most common (and very accurate), but NAD83 and NAD27 are also very, very common, as well as many others. If someone gives you a lat/long in NAD27 (e.g. read off of a printed map) and you assume it's WGS84, you can wind up over a kilometer away from the original location. (NAD27 is reasonably accurate for the US, but is very inaccurate elsewhere on the planet. I regularly see it used for data everywhere, though.)
I was trying to contrast to the case of just typing it into some kind of map service, i.e. MapCodes. A lat/long pair unambiguously resolves to a single point in that service.
That's a much smarter idea than this mapcode system. It would make sense to replace the base-10 representation with base 36.... at least in the Roman alphabet. It would probably be smarter to pick a base that works with the world's alphabets. Oh yeah, not all the world uses alphabets!
But even then, it's not that huge of an improvement, really! Every two digits of base 36 replace three digits of base 10. (36^2 = 1296). The b36 digits replace only 4 (or 4.5) base 10 digits. 4x b36 digits replace 6 base 10 digits.
I think this may actually just be the Ham radio grid system I mentioned elsewhere.
> For things like a loose description that might not be associated with a single point (e.g. "Central Park"). Here, I could see mapcodes being useful -- you can provide the precise boundaries of the park, where it's located, associate metadata with the mapcode like what hours the park is open, etc.
Heh, at this point, I'm just thinking "URL". After all, it's a Universal resource locator. How about mapcode://CentralPark/my_favorite_bench.
> Mapcodes can be easily translated between several different alphabets. The default system is based on the roman alphabet. Mapcodes in other alphabets are generated by character substitution.
And it's not based on representation of lat/lng, which is why it's more of an improvement:
> As explained in the previous section, by reserving short codes for the most densely populated areas, mapcodes for addresses (i.e. places that people need to visit) are on average as short as theoretically possible, within the limits we set for ourselves. One such limit is to use only rectangular areas in our definitions. Another is to limit the size of the “context” data table to about 16,000 records. Probably the most relevant design choice was the choice of character set. For example, had we allowed both capital and lowercase letters, 3 times as many people could have 5-letter codes instead of 6-letter codes.
> The mapcode system allows about 100 km2 of a territory to be covered by 4-letter mapcodes. These are usually reserved for the capital city. About 6,000 km2 can be covered by 5-letter mapcodes . Roughly 250,000 km2 can be covered by 6-letter mapcodes. If a territory is larger than that, the remainder requires 7 letters. A few territories on Earth (notably, Australia, Brazil, Canada, China, India, Mexico, Russia and the USA) are large enough to merit 8 letters, but these actually consist of sub-contexts, i.e. people there live in a state, republic or oblast much like people elsewhere live in a country. Within such a sub-context, mapcodes are shorter.
For example, they have 0C.T4 and they say it's in Ireland and appears to be some bench in the picture.
However, if you use that MapCode, you will see it's the middle of some river in Amsterdam.
0C.T4 == 52.369764, 4.868898
Another:
81.J4W They seem to claim it's in Alaska, appears to be some road. However, it's another river in Amsterdam.
81.J4W == 52.508957, 4.769173
I'll cite a .doc file here, it's also available on the Developers page:
> 1. Codes only need to be accurate enough for public, every-day use. At the human scale, when you are within a few meters of a destination, you are “there”.
> 4. People live within a “country context”. Addresses seldom include a country name. Unless clearly stated otherwise, they can safely be assumed to be in “this” country. Codes that are known to be within a particular territory can be designed to be much shorter. For example, every location in The Netherlands can be uniquely specified with at most 6 letters . Even in a large country like India, at most 7 letters are needed.
> 6. Short codes are reserved for areas where the population density is high. For example, every locations in The Netherlands can be represented by a unique 6-letter mapcode. However, the majority of the population is concentrated in a dozen urban areas totaling less than 3,000 km2 (1,800 square miles). By reserving the 5-letter mapcodes for these areas, half the population of The Netherlands can be found using 5-letter codes. On average, mapcodes for relevant locations in The Netherlands are thus closer to 5 letters than to 6 letters. In fact, a significant percentage of the population can be found in 100 km2 of city centers, which can be covered by 4-letter mapcodes.
> Based on these ideas, we envisaged a system that would work anywhere on Earth, and would (on average) provide the shortest possible codes to everybody. By using massive amounts of data gathered over the past 30 years by mapping company Tele Atlas (merged into the TomTom Group in 2008), a data table was constructed ...
> Finally, on top of any and all national mapcodes a location may have, it also always has a 9-letter, context-less map code.
> To understand mapcode accuracy, you need to understand that a specific mapcode defines a specific location X, but represents all the locations within a certain distance meters of X. For example, the Dutch mapcode “49.4V” decodes into coordinate 52.376514, 4.908542. This does not only mean that coordinate 52.376514,4.908542 can be represented by mapcode 49.4V, but that all coordinates within roughly 5 meters of that coordinate can also be represented by mapcode 49.4V.
(it continues to describe "high-precision mapcodes")
Why did they make it?
> The mapcode system was revived and worked out in 2006 when TomTom decided to expand their operations to countries like India and China. It was difficult to sell navigation devices in these countries, among other things because a significant part of the population lives without address, lacking not just house numbers but often even street names, which often made it hard or even impossible to enter a destination. It was thought that the introduction of a simple and ubiquitous system for representing locations (and hence destinations) would in due time make navigation devices as welcome there as anywhere else.
So if you go to the interactive map on the mapcodes site, there's a little link marked context and you need to change that to Ireland. Results in this:
http://www.mapcode.com/getcoords.html?iso3=125&mapcode=0C.T4...
It looks like the mapcodes are country specific, and two countries can have the same mapcode.
http://www.mapcode.com/downloads.html
'Unfortunately, a large part of the world population has no address. In India alone, well over half a billion people live in houses that have no street name. Millions of man-hours are lost every day trying to locate or deliver goods to people and businesses based on business cards like this:
------------------------------------------------------
Amri Patel, consultant New Sun Technologies, District 14, Pune Tel. +23984982217
Three miles east along the airport road, take second left past the golden statue, in the fourth street left ask final directions at baker across from white house.
Figure 1. Typical Indian Business Card
------------------------------------------------------
As we all know, even having an address is only an initial step in locating a position. Knowing someone lives on Queens’ Road 123 in Brunnock still requires you to find out where Brunnock is, and where the Queen’s Road is, and where number 123 is.
The mapcode system was designed as a free, brand-less, international standard that allows any location on the surface of the Earth to be represented by a short, easy to recognize and remember “code”, usually consisting of between 4 and 7 letters and digits.'
So, your point number 2 seems closest to what they're aiming for. Indeed, later in the document, they state:
'The longer a code gets, the more awkward it becomes to use, the more difficult to remember, the more easy to make mistakes in copying or using, the less benefit it offers over more elaborate descriptions. Many other benefits depend on mapcodes being short. If length was not a problem, we might as well put our longitude and latitude on business cards and address labels.'
> Also, won't there be multiple mapcodes for a single spot and won't that require cross-association of the respective metadata?
It seems like this corresponds to a coordinate system. You say what country you're in and then this gives you an aim point. I don't think you need to say 'it's in This, which is in This which...' :/
You can effectively sort on partials and get high accuracy.
For instance, the office I used to work in handled all of 421xx, 426xx and 436xx, as well as a few of the 430xx range.
Sorting was done by bucket sort (literally) on the top 3 digits in a central distribution location (all 5 for those like 430xx that was handled out of several offices), then distribution to each mail office, then another bucket sort on the full five digits, followed by another bucket sort on (roughly) street address, followed by a final sort on route.
This appears to lose all of that functionality.
> Mapcodes were developed in 2001 by Pieter Geelen and Harold Goddijn, soon after the GPS satellite signals were opened up for civilian use. It was decided to donate the mapcode system to the public domain in 2008.
Can we get an update to the click-baity title?
This means that the locations are controlled by a single entity together with country codes. Sure, postal codes are controlled by a single entity too, but at least they are regulated by the government using tax money instead of an arbitrary self-appointed committee.
I know it's meant to replace postal codes and not coordinates, but I'd like to see something that actually represents a place instead of an arbitrarily shaped region. OpenStreetMap's homepage happens to do this for their short URLs: http://osm.org/go/0GFeWn2RJ
Try moving on the OpenStreetMap map with the share menu opened and the short URL option selected. You'll see how it influences the short URL.
But anyway, back to replacing postal codes: the main advantage of this is that it'd be a universal and short code. In The Netherlands you could specify: NL 6114HT 41 and you'd have house number 41 at the Marktstraat (market street) in Susteren (city). Not much longer. And with this new system you'd still need to look up country-specific codes so I don't see much of an advantage.
One of the available regions is "Earth", which offers global coordinates(they're a bit longer, four or five characters on each side of the dot).
The upside of this is that it is possible to implement it completely offline, you don't need to query the regions from a database, because they're already defined. You just run the algorithm to project the local coordinates onto global coordinates, and your GPS system will handle that.
Why not just use lat, lon, which can be shorter too?
Central park, NY - 40.78 -73.97
Hyde Park, LON - 51.51, -0.17
1. This mapcode is country specific (!)
2. Many locations need altitude or fine lat,lon differences to differentiate them (e.g. blocks of flats, offices).
3. What's wrong with altitude, lat and lon on a given projection which can be as precise/imprecise as you want?
IMO it'd be better to have a hash of lat,lon,altitude which was globally unique for each level of precision.
A system like this needs to be globally unique without specifying country, or you may as well use a postcode. The only advantage over postcodes at present is it's slightly shorter.
* MapCodes are shorter by 200-300% for a given accuracy level, assuming each MapCode is prefixed by a two-letter country code for clarity.
Cons of MapCodes vs. Geohashes:
* MapCodes only offer one accuracy level, of apprx. 100 m^2 regions, whereas a Geohash can be arbitrarily accurate.
* MapCodes do not guarantee persistence. They can be redefined at any time, for any reason, at the sole discretion of the project designer, leaving you with a nonreferential or falsely referential code.
* MapCodes do not encode location data within the code, so access to the server is required at all times. If you lack internet access, or if the service is DDoSed, hacked, goes out of business, etc. your codes become useless.
Nope.jpg
"[This] issue should be prevented at all costs. The second [adding new countries] may be necessitated by changes to the world order, i.e. new countries coming into being. But unless changes are made by a single central authority, the first issue will quickly come to be."
>Mapcodes are free. They can be used by anyone, and may be supported, provided or generated by anyone, as long as this is done free of charge, conditions or restrictions
Why can't someone charge money for a service that generates mapcodes?
>The mapcode algorithms and data tables may not be altered in any way that would result in the production of different (and thus incompatible) mapcodes. The mapcode algorithms and data tables may not be used in any way to generate a different system that produces codes to represent locations.
I think this means that the source code they are distributing is proprietary, because we cannot use it for any purpose.
https://en.wikipedia.org/wiki/Universal_Transverse_Mercator_...
Speaking of current events, do Isreal and Palestine have separate MapCodes and what happens when borders shift?
* It doesn't use postal codes, which aren't really intended for use for anything but mail delivery and occasionally make that painfully apparent (such as when the boundaries are changed)
* It doesn't depend on street addresses, so it works in countries where the streets aren't reliably or intelligibly named/numbered. It also works in places where there are no streets.
* It's smarter about allocating code space than something like a 10:10 code, since e.g. not a lot of people live in the middle of the ocean (and they can always use a "fully-qualified" MapCode).
* It's super easy to read to someone over the phone, or type in from a business card, or transcribe from a sign.
A couple of uses immediately spring to mind:
* Telling an Uber/Taxi/rideshare where to pick you up when you don't have GPS/data.
* Telling a delivery drone where to deliver your package (without having to correctly remember dozens of digits of lat/long).
* And of course what it was designed for, entering a navigation location quickly.
I'm sure there are some implementation flaws, which may or may not be fatal, but I think it's pretty great.
Also, these are still hard to remember. Personally, I'm a fan of http://what3words.com/
I'm currently here: http://w3w.co/lives.fend.spent
What I'd really like is a hierarchy so that given
>lives.fend.spent
when you saw the words
>lives.fend.rabbi
you knew it was nearby, within the "fend" place or that
>lives.gopher.spoon
was within the "lives" places
I still have one of the registered domains with nothing to show for my preliminary work: www.tinynav.co.uk
I got as far as designing the encoding scheme, including a database of point types (house, utility pole, ancient monument, park, private event etc..), together with special codes for corporates to use for all their shops, fast food outlets etc.
I had the database tables worked out, populated the locations table with open source/public domain data such as civil and commercial airports and some other stuff. There was a front end that allowed for time-limited one-offs for things like 'Jo's birthday party', but then life took over!
It doesn't check out:
Surface Area of Earth: 510.1 * 10^6 km^2
Distinct map codes: 36^5 = 60.466176 * 10 ^6
Area of 1 map code = 8.4 km^2
Oh! It's narrowed by country... so it doesn't address any location on Earth. Only populated areas.
If you want to actually refer to ANY location on Earth, there's another system, Ham Radio grids. It uses four to six digits and refers to either 70x100 or 3x4 miles squared. Probably useless for the business purposes, but at least it truthfully refers to any location on Earth.
For example a location somewhere in the Atlantic off the coast of Gran Canaria is International QFLQV.29KM while some place in the el Poble Sec district in Barcelona is Spain SG.YB.
But then when I thought about it is actualy something that has troubled my quite some times.
Lat and longitudes are perfectly fine but in general they are to "simple" for people to use.
When I think of a location in the world I generally think of the country cause I know to some extent where most country's are located.
For example I would to describe some place in Miami I would describe it as in the lower right side of US and continue to work downwards from that.
MapCodes seem to be based on a similar concept (grid, sub grid, sub-subgrid), but with a bit shorter representation. The thing that worries me about using mapcodes, however, is what seem to be the arbitrary borders, order of girds, and the up-keep required for usage. [1]
There is nothing to stop us from creating shorter UTM Codes, though.
Assume 0->33 represented by
0 0 0 0
ABCDEFGHJKLMNPQRSTUVWXYZ0123456789
The CN Tower is at
* WGS84: 43°38′33.24″N 79°23′13.7″W, (26 chars)
* UTM: 17N 630084 4833438 (18 chars)
* "Shortened" UTM: T.N.SBB6.DW9F8 (13 chars)
* Map Code: CAN PYLK.XY8P [3] (13 chars)
So I guess the utility of such a complex system is lost on me when something like UTM, that can be decoded with minimal effort, is just as good.
[0]: http://en.wikipedia.org/wiki/Universal_Transverse_Mercator_c...
[1]: http://www.mapcode.com/mapcode_documentation.doc
[2]: http://www.mapcode.com/alphabets.html
[3]: http://www.mapcode.com/getcoords.html?iso3=112&ifrom=aboutmc
So that makes the difference between saying it to someone and having to write it down. Mapcode is massively shorter for local locations which is exactly what sat-nav is for.
The "grids" for mapcode are human-understandable - country and state.
I think a lot of HNers are thinking too much like programmers and forgetting that people need to tell each other locations and write them down. That's where mapcode is good.
This is unique within Canada and the physical area is small enough to be sufficiently useful for navigation. Add country code and it gets you to 9 or 10 chars.
UK has similarly useful alphanumeric postcodes and specifying them for satnav is the norm.
Slightly off topic, but I'm stupefied at how much faster TomTom's maps (and Bing, apparently!) are than GoogleMaps.
(unless they can convince every postal service in the world to throw away hundreds of years of dogma)
If I understand this correctly, it means that any address in a disputed territory has multiple mapcodes, one for each claimant, and therefore whichever one you use you are implicitly backing one political claim over the others.
If so, this is a potential can of worms that many people won't want to open.
Developer downloads here: http://www.mapcode.com/downloads.html?iso3=112&mapcode=49.4V
This is patented, with an ISO standard in progress, and the following licensing terms (from their developer page):
The mapcode algorithms and data tables may not be
altered in any way that would result in the production
of different (and thus incompatible) mapcodes. The
mapcode algorithms and data tables may not be used in
any way to generate a different system that produces
codes to represent locations. In order to prevent
misuse, unauthorised alterations, copying or commercial
exploitation, please note that the ideas and algorithms
behind the mapcode system have been patented and that
the term "mapcode" is a registered trademark of the
Stichting Mapcode Foundation.
Unfortunately, a large part of the world population has no address. In India alone, well over half a billion people live in houses that have no street name.
They play some interesting tricks with population density and country "contexts" to shorten codes:
4. People live within a “country context”. Addresses seldom include a country name. Unless clearly stated otherwise, they can safely be assumed to be in “this” country. Codes that are known to be within a particular territory can be designed to be much shorter.
6. Short codes are reserved for areas where the population density is high.
...a free, open way to make every house ...
The mapcode algorithms and data tables may not be
altered in any way
From the patent I get the feeling that it's a bit like a C-ary space partitioning, where C is 36 (alphabet+numbers). So the first character divides the earth in 36 regions, the second character divides that region in 36 regions, and so on.
With that in mind, I think once people would be a bit familiar with the general numbers for regions it would be pretty easy to identify what general region a mapcode would be in. So it might be a pretty good replacement of postcodes.
Or am I missing some other fundamental property of postcodes?
[1] http://en.wikipedia.org/wiki/Geohash [2] http://geohash.org/9q8yyvfekk8h
Something like DE.BERLIN.2.1H
First, human readable part defines a look-up to defined geohash of center of region on a given level.
So DE.BERLIN could resolve to u33, u33d or u33db (length/level 5) the last one seems reasonable, since a few multiples of the area cover the whole city of Berlin
Second, optional, part encodes offset of Z-Curve index of location at same zoom level.
Z-Curve on globe: http://www.bigdatamodeling.org/2013/01/intuitive-geohash.htm...
This enables global coverage at any level if needed, and makes the code robust to administrative changes that affect the area of the given region! The offset part could start at 1 and alternate the sign with each increment.
isOdd(offsetPart) ? -(offsetPart-1)/2 : offsetPart/2;
1 → 0, 2 → 1, 3 → -1, 4 → 2
An offset part of 1 equals an offset of 0 and could be omitted.
The third part adds to the precision of that given cell.
Brandenburg Gate, within area of origin cell of region part. could be written as DE.BERLIN.1.2M3 or short DE.BERLIN.2M3
http://geohash.2ch.to/u33db2m3
DE.Berlin.2.1H would be the area and center point of the Berliner Fernsehturm with sufficient accuracy u33db + 1 = u33dc
This example uses base 32 to comply with geohash but other more error robust encodings and variations (e.g. second part as base ten numerals) could be used as well.
Add optional checksum part based on unshortened geohash if needed to verify integrity.
Variants: since geohash, covers a varying amount of area depending on the latitude. A similiar approach could be realized on a UTM based grid like MGRS if a precise area is required (https://en.wikipedia.org/wiki/MGRS)
I've written a fairly extensive GPS library for some embedded device projects in the past, and I can attest to the computer not caring about the long coordinate system, they are just floating points really.
Imagine if a URL resolved to different addresses in each country you were in. Would that be a better system than what we have now, or a worse one? I think it would self-evidently be worse.
I'm surprised they didn't make mapcodes a globally-unique identifier.
That's not true for navigation in the physical world. If you're sitting in Nebraska, how often do you have to navigate to a location in Mongolia? Approximately never! Map codes are optimized for the common case, where you want to go to a location that's nearby.
In fact, it's even more clever than that, since it defines "nearby" as a political unit. Borders may be artificial, but they're real, and crossing them has practical implications. If you're planning to buy something in another jurisdiction, there might be tax implications. You may need your passport to cross the border. You may not speak the language of that area. All of this means that having the political unit as a human-readable part of the map code is useful.
Finally, consider that some URLs do resolve differently depending on where you are. They're called relative URLs. They're very handy and very common. I'd guess that the vast majority of URLs on the web are relative. MapCodes work the same way. The code "Ireland 0C.T4" is globally unique. If you're already in Ireland, you can omit the territory, much as you would omit the country when inviting a friend to your house for dinner.
For cases where you really do have to travel to the other side of the planet, is it really so onerous to specify "Mongolia 0C.t4"?
> Finally, on top of any and all national mapcodes a location may have, it also always has a 9-letter, context-less map code.
But that's too long to use every day... It would be like requiring all streets to have globally unique names. Because they're qualified by location, you could, if you wanted to, enumerate all matches in order of distance, and in 90% of cases, that would be the location you're looking for. Better here, since many cities will have the same street names in multiple places ;-)
I see they have come up with them for all locations, but how can I take a given coordinate and surmise it's MapCode, or the reverse (without their API or website)?
> A conversion need not just be based on formulae. A respectable amount of data may be used as part of an algorithm.
Which is why when you go to the downloads page, you'll find sources in C, JavaScript and Java, but they all include "data tables".
There are a few other restrictions, though it's somewhat unclear how relevant they are here without inspecting the tables closer:
> One such limit is to use only rectangular areas in our definitions. Another is to limit the size of the “context” data table to about 16,000 records.
So it's not something you can do without the data tables. And for ease of use, they have disambiguation routines for country/state input.
They make a lot of assumptions, and a lot of hard-coded values.
For example, they seem to have lots of city names and country names hard-coded into a giant String array. ISO country codes are hard-coded (probably a safe assumption so-long as new countries are not added), many "magic numbers".
Overall, I think these things are acceptable... but I don't necessarily like relying on the assumptions that "things today should be the same tomorrow". With plain old coordinates, my software would never care if the ISO added new country codes or what-have-you.
I see they intent this to be mainly for human consumption -- but is US-AK 81.J4W really any more memorable than 52.508957, 4.769173? I'd probably end up writing both down personally, which means the coordinates would suit me just fine.
It's much harder to hear "eight" and mistake it for another number, but "P" and "T" are commonly confused (presumably people would read it as "Papa" and "Tango" to avoid confusion). What about "O" and "0", "I", "l", "1", etc. Now we have ambiguities that may not be interpreted correctly, even with phonetics.
One could argue either way about fully-numeric versus alphanumeric codes. They're a bit harder to communicate but more than three times shorter, on average.
Edit: math is hard. One and a half times shorter, on average.
