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Comment by londons_explore | Hacker News Reader

But now all the complex math is hidden away behind abstractions, and the extra computation to do everything in WGS-84 space is insignificant. Yet the benefits are huge in that every engineer who works on the design won't need all this extra knowledge of many custom coordinate systems and the way conversions and interactions between them work. Not to mention the huge possible costs when someone messes up and uses the wrong coordinate system for something and a beam ends up only half the thickness it should have been because the top was constrained by something in one coordinate system and the bottom by something in another...

I think a close parallel is the complexity of UTF-8 is now worth it over encoding things using codepages.

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> But now all the complex math is hidden away behind abstractions, and the extra computation to do everything in WGS-84 space is insignificant... UTF-8 is now worth it over encoding things using codepages.

There is a reason for having GIS professionals. WGS-84 is not nearly accurate enough for many purposes. Good enough to find your home, not good enough for precision surveys. In my country to get sub-metre (cm) precision using NZGT2000 is necessary.

WGS-84 also has no deformation component. The tectonic plates moves, in parts of my country movement is 5cm/year,and so a WGS-84 coordinate taken at one point in time won't precisely point to the save bit of dirt at a later time. Other geographic coordinate systems can take this into account.

Nobody would use UTF-8 if every 1000th character was lost.

With a dual band survey grade receiver, WGS84 coordinates can be derived to 2cm accuracy in the vertical [0] and even better in the horizontal.

WGS 84 is a time dependent datum - each addition to the ensemble is known as a realization. The software used to convert across time and reference frames is called HTDP [1]. This can also be done for the vertical using VDatum, which wraps HTDP.

The confusion around this issue usually has to do with how analysts actually handle coordinate information in software. For example ESRI, arguably the dominant GIS, does not have time dependent conversion capability. In the US there is also a false equivalence that NAD83 == WGS84. Looks like NZ has a similar issue [2].

Developers also have to deal with this issue, since web mercator and the tiling scheme were designed for convenience and not sub meter accuracy.

[0] https://www.ngs.noaa.gov/PUBS_LIB/NGS592008069FINAL2.pdf [1] https://www.ngs.noaa.gov/TOOLS/Htdp/Htdp.shtml [2] https://www.linz.govt.nz/data/geodetic-system/datums-project...

> With a dual band survey grade receiver, WGS84 coordinates can be derived to 2cm accuracy in the vertical [0] and even better in the horizontal.

Accuracy or precision? The issue is accuracy, not precision.

> Developers also have to deal with this issue, since web mercator and the tiling scheme were designed for convenience and not sub meter accuracy.

This is a projection problem. All projections are essentially wrong, and tradeoffs need to be made (eg. you can't flatten an orange on a desk without distorting some parts of it) . Unfortunately users don't understand this which is why people get excited when they discover America is smaller, and Africa larger, than they thought. Ideally when zooming into a country a more suitable projection would be used, but at the end of the day it doesn't matter much for consumers.

I think software developers don't give GIS developers enough credit. Software devs will endless debate and be critical of floating point issues, but also not consult with a GIS professional when doing spatial work. People don't know what they don't know.

> the extra computation to do everything in WGS-84 space is insignificant

There is still significant overhead involved in conversion - arbitrary trig functions, even optimised, are still really expensive compared to planar geometry. Remember these folks will be working at super high resolutions too.

Isn't another issue also that WGS-84 is fixed globally, which'd mean that due to continental drift, local coordinates would be constantly shifting? Whereas the current local grids are usually fixed with regards to the local continental plate, so coordinates remain relatively stable-ish because the whole local grid moves together with the continental plate.

I was thinking about mentioning that... yes! Construction on this project began 13 years ago so it needs to be taken into consideration. A similar project in Australia would've seen a drift of up to several metres in this time [0]. Europe has another angular CRS for this reason [1].

[0]: https://theconversation.com/australia-on-the-move-how-gps-ke...

[1]: https://www.killetsoft.de/t_1009_e.htm

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