[Therion] 3D model height

Balambér Hakapesz holl.balazs63 at gmail.com
Fri Feb 19 12:06:08 CET 2021 

The error only occurs when using the EOV (EPSG: 23700) coordinate system.

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On Fri, Feb 19, 2021 at 11:59 AM Balambér Hakapesz <holl.balazs63 at gmail.com>
wrote:

> # 2021.02.08 created by TopoDroid v 5.0.79
>
> #source "../th/kml.th"
> source "kml.th"
>
> layout topodroid
>   legend on
>   symbol-hide group centerline
>   symbol-show point station
>   debug station-names
> endlayout
>
> export map -layout topodroid -o kml-p.pdf -proj plan
>
> export map -layout topodroid -o kml-s.pdf -proj extended
>
> # export model -fomat survex -o kmlth.3d
>
> export model -output kmlo.3d
> export model -output kmlo.lox
> export model -output kmlo.dxf
> export model -output kmlo.kml
>
>
>
> # 2021.02.08 created by TopoDroid v 5.0.79
>
> survey kml -title "kml"
>
>   centerline
>     #cs long-lat
>     #fix 0 19.009617 47.526453 262
>     cs EPSG:23700               #ez felel meg az EOV-nek
>     fix 0 647151 242509 262
>     date 2021.02.08
>     # declination 5.0000 degrees
>     units length meters
>     units compass clino degrees
>     data normal from to length compass clino
>     extend right
>     0 1 10.00 180.0 -90.0
>     1 2 10.00 0.0 0.0
>     2 3 10.00 90.0 0.0
>     units left right up down meters
>     data dimensions station left right up down
>   endcenterline
>
> endsurvey
>
>
>
>
>
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>
> On Fri, Feb 19, 2021 at 11:49 AM Benedikt Hallinger <beni at hallinger.org>
> wrote:
>
>> What does the survex/aven file give you, is the error there also
>> apparent?
>>
>> What is your full thconfig file for generating the kml and aven .3d?
>>
>> Dies the problem also exists when specifying this:
>>    cs EPSG:4326
>>    fix 0 19.009617 47.526453 262
>>
>>
>>
>> Am 2021-02-19 11:25, schrieb Balambér Hakapesz:
>> > If I were to enter the ellisoid height, the error of Proj4 would still
>> > remain on the EOV projection.
>> > I could work in a UTM coordinate system, but it would be much simpler
>> > if Therion didn’t recalculate anything. (There is no height issue
>> > between UTM and WGS84 because there is no conversion)
>> > This error is only present in the national projections where Proj4
>> > performs approximate calculations for the advantage of horizontal
>> > coordinates and the disadvantage of height.
>> >
>> > On Fri, Feb 19, 2021 at 11:25 AM Balambér Hakapesz
>> > <holl.balazs63 at gmail.com> wrote:
>> >
>> >> thconfig:
>> >> #cs long-lat
>> >> #fix 0 19.009617 47.526453 262
>> >> cs EPSG:23700               # Hungarian EOV
>> >> fix 0 647151 242509 262
>> >>
>> >> kml:
>> >> <LineString><coordinates>
>> >> 19.00961011626948,47.52649337576407,291.08568208889801
>> >>
>> >> 291-262 = 29 m = 44m geoid height - 15m Proj4 error
>> >>
>> >> [2]
>> >> Mentes a vírusoktól. www.avg.com [2]
>> >>
>> >> On Fri, Feb 19, 2021 at 11:06 AM Benedikt Hallinger
>> >> <beni at hallinger.org> wrote:
>> >>
>> >>> Isn't EGM84 the reference ellipsoid currently used by WGS84?
>> >>> What you get with GPS is *not* sea level, but the altitude above
>> >>> that
>> >>> reference geoid (which takes into account gravital anonalys).
>> >>>
>> >>> If you calibrate your barometric altimeter to the hieght given by
>> >>> a
>> >>> height coordinate of WGS84 (like read from your car's navi at the
>> >>> parking lot, or from a map calibrated to WGS84) then you should
>> >>> get
>> >>> about the same altitude.
>> >>> If you take the cave location from GPS and enter that coordinates
>> >>> into
>> >>> the therion dataset wirh correct "cs" marking, the conversion
>> >>> should
>> >>> yield the correct result.
>> >>> If you take the altitude from a map (or an altimeter calibrated to
>> >>> that
>> >>> map) in another coordinate system, you have to either apply an
>> >>> offset
>> >>> manually, add an instrument correction factor in therion, or
>> >>> supply the
>> >>> correct coordinate system (which then probalby demands conversion
>> >>> of the
>> >>> lat/lon coordinates).
>> >>>
>> >>> If generating 3D surfce meshes, you also need to supply matching
>> >>> coordinate systems data and/or specify the correct "cs" parameter.
>> >>>
>> >>> I think your problem comes from mixing coordinate systems in
>> >>> respect to
>> >>> the height model, either at data input or when using the height
>> >>> mesh.
>> >>>
>> >>> Am 2021-02-19 9:49, schrieb Balambér Hakapesz:
>> >>>> Very rarely can anyone work at ellipsoidal heights. In local
>> >>>> coordinate systems, it only makes sense for upper geodetic
>> >>>> calculations. Only for GPS measurements we get an ellipsoidal
>> >>>> altitude, even there the devices can immediately calculate the
>> >>>> altitude of the EGM96 model with an altitude above sea level
>> >>> (with a
>> >>>> few meters error which is not significant compared to the 15m
>> >>> altitude
>> >>>> error of handheld GPS).
>> >>>> Proj4 calculates the horizontal coordinates well, but there is a
>> >>>> serious error in the height coordinates (for special national
>> >>>> projections
>> >>>>
>> >>>
>> >>
>> > (http://www.agt.bme.hu/gis/workshop4/eloadasok/proj_poszter_3d.pdf)),
>> >>>> so it would be better if not we would count on it but leave the
>> >>>> altitude unchanged.
>> >>>> Could it be an option not to change the height with Therion?
>> >>>>
>> >>>> [2]
>> >>>> Mentes a vírusoktól. www.avg.com [1] [2]
>> >>>>
>> >>>> On Fri, Feb 19, 2021 at 9:18 AM Benedikt Hallinger
>> >>>> <beni at hallinger.org> wrote:
>> >>>>
>> >>>>> Hi there,
>> >>>>> if you measure the altitude with a barometric device, you do
>> >>> not get
>> >>>>> the
>> >>>>> altitude above the ellipsoid. You have to account for that at
>> >>> the
>> >>>>> input
>> >>>>> of your data.
>> >>>>>
>> >>>>> With the "cs" command you define your input data to be in a
>> >>> specific
>> >>>>>
>> >>>>> coordinate system, and also your altitude has to be given in
>> >>> that
>> >>>>> system. If you just put the barometric altitude there (which
>> >>> you
>> >>>>> usually
>> >>>>> did calibrate to a map, didn't you?) you have to transform the
>> >>>>> altitude
>> >>>>> manually if the reference altitude differs.
>> >>>>>
>> >>>>> Am 2021-02-19 8:44, schrieb Balambér Hakapesz:
>> >>>>>> Hi!
>> >>>>>>
>> >>>>>> When generating 3D models, Proj4 transforms between different
>> >>>>>> coordinate systems.
>> >>>>>> This also transforms the ellipsoidal altitude, but the data
>> >>> always
>> >>>>>> refer to altitude above sea level and should not be changed.
>> >>>>>> The finished models do not fit the topography, you have to
>> >>> cheat
>> >>>>> with
>> >>>>>> the height to be good.
>> >>>>>>
>> >>>>>> Balázs Holl.
>> >>>>>>
>> >>>>>> [1]
>> >>>>>> Mentes a vírusoktól. www.avg.com [1] [1] [1]
>> >>>>>>
>> >>>>>>
>> >>>>>>
>> >>>>>> Links:
>> >>>>>> ------
>> >>>>>> [1]
>> >>>>>>
>> >>>>>
>> >>>>
>> >>>
>> >>
>> >
>> http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail
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>> >>>>> Therion mailing list
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>> >>>>> https://mailman.speleo.sk/listinfo/therion
>> >>>>
>> >>>>
>> >>>> Links:
>> >>>> ------
>> >>>> [1] http://www.avg.com
>> >>>> [2]
>> >>>>
>> >>>
>> >>
>> >
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>> >>
>> >> [2]
>> >> Mentes a vírusoktól. www.avg.com [2]
>> >
>> >
>> > Links:
>> > ------
>> > [1] http://www.avg.com
>> > [2]
>> >
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