<div dir="ltr">Hi,<div><br></div><div>Proj 4 and 5 uses a different conversion than Proj 6+ resulting in the height difference.</div><div><br></div><div>Actually, the behaviour of Therion was inconsistent: when doing internal conversions it transformed only x and y coordinates, but when creating e.g. KML output it transformed all x, y and z coordinates. The latest commit (b6bcc92) unifies this to converting just x and y for all coordinate systems transformations.</div><div><br></div><div>If there is a real need for a switch between converting and not converting the heights, let us know.</div><div><br></div><div>Martin</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Feb 19, 2021 at 8:41 PM Balambér Hakapesz <<a href="mailto:holl.balazs63@gmail.com">holl.balazs63@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">therion 5.5.7+0df52bd+dev (2021-02-18)<br> - using Proj 5.1.0, compiled against 5.1.0<br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Feb 19, 2021 at 8:40 PM Balambér Hakapesz <<a href="mailto:holl.balazs63@gmail.com" target="_blank">holl.balazs63@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div>latest Therion 5.5.7 (now install):</div><div><br></div><LineString><coordinates><br> 19.00961011626948,47.52649337576408,<b>291</b>.08568208824045 19.00961011450532,47.52649337534078,281.08568208855468 19.00962225574169,47.52658294585592,281.08562306819113 19.00975449765885,47.52657472222689,281.08549506128293 <br></coordinates></LineString><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Feb 19, 2021 at 8:19 PM Martin Budaj <<a href="mailto:m.budaj@gmail.com" target="_blank">m.budaj@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr">Hi,<div><br></div><div>which version of Therion and Proj are you using? I get</div><div>19.00961002698361,47.52649340144701,262.00000000000000<br></div><div>in the kml export with the latest Therion and Proj 7.2.1</div><div><br></div><div>Best wishes</div><div>Martin</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Feb 19, 2021 at 11:25 AM Balambér Hakapesz <<a href="mailto:holl.balazs63@gmail.com" target="_blank">holl.balazs63@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">thconfig: <div>#cs long-lat<br> #fix 0 19.009617 47.526453 262<br> cs EPSG:23700 # Hungarian EOV<br> fix 0 647151 242509 262<div><br></div><div>kml:</div><div><LineString><coordinates><br> 19.00961011626948,47.52649337576407,291.08568208889801 <br><div><br></div><div>291-262 = 29 m = 44m geoid height - 15m Proj4 error</div></div></div><div><br></div></div><div id="gmail-m_1264032343771874480gmail-m_-3468513418640853693gmail-m_2109412960721514408gmail-m_-5536043658431662593DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br> <table style="border-top:1px solid rgb(211,212,222)">
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<a href="#m_1264032343771874480_m_-3468513418640853693_m_2109412960721514408_m_-5536043658431662593_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2" width="1" height="1"></a></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Feb 19, 2021 at 11:06 AM Benedikt Hallinger <<a href="mailto:beni@hallinger.org" target="_blank">beni@hallinger.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Isn't EGM84 the reference ellipsoid currently used by WGS84?<br>
What you get with GPS is *not* sea level, but the altitude above that <br>
reference geoid (which takes into account gravital anonalys).<br>
<br>
If you calibrate your barometric altimeter to the hieght given by a <br>
height coordinate of WGS84 (like read from your car's navi at the <br>
parking lot, or from a map calibrated to WGS84) then you should get <br>
about the same altitude.<br>
If you take the cave location from GPS and enter that coordinates into <br>
the therion dataset wirh correct "cs" marking, the conversion should <br>
yield the correct result.<br>
If you take the altitude from a map (or an altimeter calibrated to that <br>
map) in another coordinate system, you have to either apply an offset <br>
manually, add an instrument correction factor in therion, or supply the <br>
correct coordinate system (which then probalby demands conversion of the <br>
lat/lon coordinates).<br>
<br>
If generating 3D surfce meshes, you also need to supply matching <br>
coordinate systems data and/or specify the correct "cs" parameter.<br>
<br>
I think your problem comes from mixing coordinate systems in respect to <br>
the height model, either at data input or when using the height mesh.<br>
<br>
<br>
Am 2021-02-19 9:49, schrieb Balambér Hakapesz:<br>
> Very rarely can anyone work at ellipsoidal heights. In local<br>
> coordinate systems, it only makes sense for upper geodetic<br>
> calculations. Only for GPS measurements we get an ellipsoidal<br>
> altitude, even there the devices can immediately calculate the<br>
> altitude of the EGM96 model with an altitude above sea level (with a<br>
> few meters error which is not significant compared to the 15m altitude<br>
> error of handheld GPS).<br>
> Proj4 calculates the horizontal coordinates well, but there is a<br>
> serious error in the height coordinates (for special national<br>
> projections<br>
> (<a href="http://www.agt.bme.hu/gis/workshop4/eloadasok/proj_poszter_3d.pdf)" rel="noreferrer" target="_blank">http://www.agt.bme.hu/gis/workshop4/eloadasok/proj_poszter_3d.pdf)</a>),<br>
> so it would be better if not we would count on it but leave the<br>
> altitude unchanged.<br>
> Could it be an option not to change the height with Therion?<br>
> <br>
> [2]<br>
> Mentes a vírusoktól. <a href="http://www.avg.com" rel="noreferrer" target="_blank">www.avg.com</a> [2]<br>
> <br>
> On Fri, Feb 19, 2021 at 9:18 AM Benedikt Hallinger<br>
> <<a href="mailto:beni@hallinger.org" target="_blank">beni@hallinger.org</a>> wrote:<br>
> <br>
>> Hi there,<br>
>> if you measure the altitude with a barometric device, you do not get<br>
>> the<br>
>> altitude above the ellipsoid. You have to account for that at the<br>
>> input<br>
>> of your data.<br>
>> <br>
>> With the "cs" command you define your input data to be in a specific<br>
>> <br>
>> coordinate system, and also your altitude has to be given in that<br>
>> system. If you just put the barometric altitude there (which you<br>
>> usually<br>
>> did calibrate to a map, didn't you?) you have to transform the<br>
>> altitude<br>
>> manually if the reference altitude differs.<br>
>> <br>
>> Am 2021-02-19 8:44, schrieb Balambér Hakapesz:<br>
>>> Hi!<br>
>>> <br>
>>> When generating 3D models, Proj4 transforms between different<br>
>>> coordinate systems.<br>
>>> This also transforms the ellipsoidal altitude, but the data always<br>
>>> refer to altitude above sea level and should not be changed.<br>
>>> The finished models do not fit the topography, you have to cheat<br>
>> with<br>
>>> the height to be good.<br>
>>> <br>
>>> Balázs Holl.<br>
>>> <br>
>>> [1]<br>
>>> Mentes a vírusoktól. <a href="http://www.avg.com" rel="noreferrer" target="_blank">www.avg.com</a> [1] [1]<br>
>>> <br>
>>> <br>
>>> <br>
>>> Links:<br>
>>> ------<br>
>>> [1]<br>
>>> <br>
>> <br>
> <a href="http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail" rel="noreferrer" target="_blank">http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail</a><br>
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> <br>
> <br>
> Links:<br>
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> [1] <a href="http://www.avg.com" rel="noreferrer" target="_blank">http://www.avg.com</a><br>
> [2]<br>
> <a href="http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail" rel="noreferrer" target="_blank">http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail</a><br>
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