[Therion] 3D model height

[Balambér Hakapesz]

67fffb0 installation does not work on Windows7

Balázs.

On Mon, Feb 22, 2021 at 10:28 PM Balambér Hakapesz <holl.balazs63 at gmail.com>
wrote:

> No, the issue is the difference between the altitudes of the mean sea
> level (geoid) and the ellipsoidal coordinates.
>
> Balázs.
>
> On Mon, Feb 22, 2021 at 10:22 PM Benedikt Hallinger <beni at hallinger.org>
> wrote:
>
>> As far as i understood, when you tag your data to be in a certain
>> coordinate system that should include all three data points when the
>> coordinate system defines them.
>> If you want an altitude offset, i would expect that we must manually
>> convert.
>>
>> As an example: i tag my data to be wsg89, which defines altitude pegged
>> to a certain reference.
>> Assume alt is 0.
>> When i now switch coordinate systems to something really (artifically)
>> weird, like the origin pegged to the peak of mt. Everest, i would expect
>> all three coordinates to be correctly transformed (making especially
>> altitude very negative).
>> If i now want to say that a point is at the same level as everests peak,
>> i would have to apply a manual transformation step.
>> But that’s not the fault of wgs89 mir the target cs, the reason was that
>> my initial calibration was never in wgs89!
>>
>> What do i get wrong in this thought process?
>>
>>
>> > Am 22.02.2021 um 21:37 schrieb Tarquin Wilton-Jones via Therion <
>> therion at speleo.sk>:
>> >
>> > 
>> >>
>> >> If there is a real need for a switch between converting and not
>> >> converting the heights, let us know.
>> >
>> > At least here in the UK, a lot of rough and ready surveys seem to use
>> > Garmin handheld GPS units like the 66sr. These use barometric altitude,
>> > which you calibrate to a local benchmark. That means you get local
>> > mapping heights that do not need to be converted, while the GPS
>> > coordinates would need to be converted.
>> >
>> > Anyone relying on this approach (which already is rather poor from an
>> > accuracy perspective) would indeed need you to perform conversion on x
>> > and y but not z, while anyone using a proper GPS unit which outputs
>> > ellipsoid heights would need you to convert x, y, and z. I therefore see
>> > a need for it to be controllable.
>> >
>> > Personally, I use real GPS ellipsoid heights, which I manually convert
>> > using continental drift calculations and the higher quality
>> > OSTN15+OSGM15 transformation (since these then remain correct in spite
>> > of continental drift). I do not rely on proj for that, and have built my
>> > own tool instead, since proj does not have access to the data required
>> > for it.
>> >
>> > Tarquin
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