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    Do programmers actually believe these falsehoods? They seem specific enough that anybody working in the domain would know these.

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      Geodesy and mapping are both quite complicated and there’s a lot of stuff to keep in mind. When I started a few years ago I definitely was not aware of all the complexities I know about now, and I’m sure I remain ignorant of yet more.

      An example might be that data in Open Street Map usually doesn’t have an associated reference frame, it’s just presented as WGS84 lat/lon, but anything with sub-meter accuracy must be relatable to a reference frame, usually one of the ITRF frames, or you can’t meaningfully interpret it.

      Another example that I suspect most people doing data-science with geospatial data are ignorant of is that heights are preserved very badly in much of the world by the WGS84 geoid (tho with the EGM96 it is better). But the fit is good across North America, so it would be easy for yanks to miss. This can have practical effects (as I recall sea level in Cornwall is about 100m wrong in WGS84, so you need to adjust for that). The locally poor height fit of WGS84 is why the UK used to use its own geoid (we still sort of do, but it’s defined in relation to a version of ITRF now) and is probably part of why China and Russia still use their own.

      Lots of these issues can bite you hard, but often don’t, which is why they are easy to miss. You can get away with using an inappropriate UTM grid; or calculating distances naively with euclid and lat/lon; or ignoring the issues with high-precision data. Things will mostly work.

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        “programmers” don’t think about these, so they likely have some/most of these assumptions. When I was working in a field which involved mapping these were said in the onboarding to the project, thus likely the prior experience was most programmers don’t know these, so it is better to tell them upfront. (I did have prior knowledge on the topic from astronomy though)

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          No, but it still seems like a good list.

          I’ve tangentially worked with map data in the last few years and half of those were new to me, because they didn’t exactly apply to our problems.

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            I worked in geospatial stuff for a while. You run into this stuff, these vocabulary terms, constantly, but they complex enough that in a sufficiently large team you will still constantly see mistakes. What’s worse is some fraction of the time the mistakes lead only to very subtle data errors. You end up with a class of geospatial professionals who are implicitly qualified enough to review all geospatial code and check up on subtle data distortion.

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            I’m pretty sure most programmers who are new to GIS etc. will make an effort to study the intricacies involved. Unlike previous popular “falsehoods programmers believe”, namely names and dates, map coordinates simply don’t have the ingrained assumptions people have with the previous areas.

            Edit to expand, what I’m trying to say is that it’s vastly more common for developers to deal with names and dates than it is to deal with coordinate systems - especially for mission critical applications such as surveying.

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              While that’s true, the inherent complexity of geospatial issues feels a bit higher. In practice, there are geospatial experts who do this all the time and know the ins and outs, geospatial tourists who just need to touch some well-behaved corner of this, and then the mixed teams where the experts have to deal carefully with the tourists learning their way through the minefield.

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                It seemed a very strange list. I don’t think I believed any of them. Some were things I knew were obviously wrong (e.g. one degree is a fixed distance), some of the others were things that I didn’t believe because I didn’t know enough about GIS to get to the basic level of misunderstanding (e.g. I have never heard of web mercator, though I did know non-mercator projections were important). It seems like you have to go down a particularly odd learning path to get to these beliefs: you need a lot of domain-specific knowledge with no context.

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                  I realize the author wanted to riff off the famous “Falsehoods programmers believe…” about names and dates, but a better title would have been “here are eight surprising facts about map coordinates you probably didn’t know”.

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                  With GPS and Google Maps being ubiquitous I think many people don’t think about these topic, but take the patterns saw there for granted.

                  People don’t know about the intricacies of timekeeping and calendaring, because watches (now phones) are everywhere. I have learnt quite a bit about them, so I don’t assume anything being simple about them. I think the situation is similar with navigation/mapping.

                  Btw. developers deal with GIS quite often in business applications/logistics. Coordinate systems often not considered in those cases, until they pop out from a hidden corner, and then are used incorrectly :)