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Comment by AlotOfReading | Hacker News Reader

GPS coordinates actually account for the motion of the Earth's tectonic plates. The problem is that it's a highly approximate model that doesn't accurately reflect areas like Australia very well.

There's a great visualizer of the coordinate velocity from the Earthscope team:

https://www.unavco.org/software/visualization/GPS-Velocity-V...

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GPS coordinates do not account for tectonic motion. It is a synthetic spheroidal model that is not fixed to any point on Earth. The meridians are derived from the average motion of many objects, some of which are not on the planetary surface.

The motion of tectonic plates can be calculated relative to this spatial reference system but they are not part of the spatial reference system and would kind of defeat the purpose if they were.

The corrections are incorporated into the datum. WGS84 is updated every 6 months to follow ITRF by changing the tracking station locations as the plates move around.

That's about correcting the ground stations' coordinates. It doesn't help keeping your house's GPS coordinates fixed. If the tectonic plate your house is built on moves a meter over the course of a decade, then your house's GPS coords will change in the lower decimals, and eventually your government's land registry will need to update those values.

Hopefully there are still governments that don’t keep such in detail land registries, or any land registries at all, for that matter. Some of us don’t want the State to see everything, at almost every moment in time.

And have endless disputes over who owns what exactly? Allow companies to kick people off their land because they can't do anything about it?

IMO having a good land ownership registry is one of the most important things to count as a developed country.

If you want to keep your land then you need to keep it in such detail in some registry.

Else it's trivial for someone to claim it or parts of it. Before such registries tons of people lost their land, lost part of their land, went bankrupt trying to save it, or murdered each other over their plots of land border dispute.

There are lots of records a state shouldn't have. Something fixed and stationary that needs protection from encroaching, like land limits, doesn't seem it should be one of them.

You made the very wrong assumption that land possession is mostly an individual thing, and second, that the State would be happy to award “common” ownership to communities big and small, and as such that it would allow said communities (in many cases much older than the State itself) to decide who gets to use what land inside of said communities. And the main reason is that the State doesn’t like, nor want, any sort of competition in this domain.

>You made the very wrong assumption that land possession is mostly an individual thing, and second, that the State would be happy to award “common” ownership to communities big and small, and as such that it would allow said communities (in many cases much older than the State itself) to decide who gets to use what land inside of said communities.

I made neither assumption, and both arguments are irrelevant to my point.

Take the current rights of anyone to one or more plots of land they own. As those are today, and also as they change while some are sold and bought etc.

To protect those rights of those onwers (of citizens and businesses and municipalities and so on) a registry or plots and their boundaries is very useful.

>to decide who gets to use what land inside of said communities

That's a totally irrelevant point, one that I didn't bring up.

I never said the state will happily "award “common” ownership to communities big and small, and as such that it would allow said communities (in many cases much older than the State itself) to decide who gets to use what land inside of said communities". In fact, for the purposes of my argument, whether the state will do that doesn't concern me at all.

Just that the state keeping a registry of plots and their boundaries helps keep track of ownership. Not transfer it to communities, to give it to someone else to administer: to keep track.

If the state doesn't know that you own a piece of land, then you don't own that piece of land. Simple as.

You simply do not own any peice of land at all. The state owns all the land. You simply lease it.

Well, in some countries this might be true.

It's true in all countries to the extent that it's true in any countries, but it's only partially true to begin with. The reality is that ownership doesn't exist. What actually exists is a credible threat to use violence if certain conditions are violated. In a civilized society this comes from the state. In a failed state it comes from somewhere else.

If WGS84 was correcting for tectonic drift it would imply that the coordinates of the terrestrial fixed points used to compute the reference meridian never change under WGS84. Rebasing the coordinates of terrestrial fixed points prior to calculation disregards tectonic drift in the reference meridian calculation, it doesn’t correct it. It is a noise reduction exercise to minimize the influence of plate tectonics on meridian drift. The meridian uses non-terrestrial fixed points too that don’t have a concept of tectonic drift (but may introduce their own idiosyncratic sources of noise).

Basically, these are corrections to their “fixed points” to make them behave more like actual fixed points in the reference meridian model. It doesn’t eliminate tectonic drift effects when using coordinates in that spatial reference system.

I'm pretty positive that is showing the reverse, i.e. how much a given "location" is moving using gps coordinates. Not adjusting the gps coordinates to refer to a constant "location".

>GPS coordinates actually account for the motion of the Earth's tectonic plates.

What?

accounts for (something), phrasal verb meaning "considers; incorporates; takes on board" as opposed to the more obvious "gives rise to; is responsible for". I had to read twice too

Yeah, I know what "accounts for" means.

I just can't comprehend how GPS coordinates could account for the tectonic plates' motion. Never heard of such a thing, and can't see how it would work on a conceptual, mathematical level.

They don't, and you're right it wouldn't make sense.

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