Record distance: Zuidertoren, Tour du Midi in Brussels seen from Waterfront   13427
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1 Cuesta of Waasmunster 32 m (B), 28-29 km
2 Top of dome Koekelberg Basilica, 100 m (+- 160 m TAW), Ganshoren Brussels, 62.3 km
3 Village Axel (NL), 9.5 km
4 Zuidertoren, Tour du Midi, 148 m (-+ 170 m TAW), Brussels, 65.8 km
5 Water tower Axel (NL), 10.2 km
6 Kartelobos, 72 m TAW, 52.1 km
7 Hospital Zorgsaam, Terneuzen, 3.7 km
8 Heights around Asse, 50 km
9 Kravaalbos/Terrenberg, 72.5 m TAW, 50.5 km
10 St Laurentius church Lokeren (B), 28 km


Location: Terneuzen, Waterfront (66 m)      by: Mentor Depret
Area: Netherlands      Date: 2018 09 07 8:04 PM st
Some time ago, I discovered the northern hills of the Flemish Ardennes (hilly region south of Ghent), at a distance of 45-48 km, are clearly visible from Waterfront (pano 23565). Additional work revealed that even the highest hill: Pottelberg, 157 m (TAW) on the border between Flanders and Wallonia (between La Houppe and Flobecq) sometimes is visible. This hill is at a distance of 64-64.5 km. I never discussed this but I will show on a next pano. So I thought, if this hill is visible, maybe some towers in Brussels, at 62 km to 67 km, are visible too. I didn’t find any data suggesting this was seen before, nor by the residents on the higher floors of Waterfront, equipped with 50x scopes.

Now the problem is that the northeastern half of Brussels, with many of the higher towers, is behind the relatively nearby Waasmunster cuesta, visible at left on this pano (left of 147°). This cuesta, only 28-29 km from here, has an elevation of 32 m TAW but is mostly covered with 10 m-20 m high trees resulting in a height of about 40 m to 50 m. So heights (terrain+building) of at least 190-200 m at 65 km, are required to stick out above the trees and they are not there.

However something of the southwestern half should be visible because that part of the city is located just right of the steep edge of the cuesta where terrain+tree heights drop to about 5+20=25 m TAW. In particular, the highest building in Belgium: Tour du Midi or Zuidertoren, 148 m (without antenna), at 65.8 km, should be visible, even taking into account that it is located in the lower parts (20-25 m TAW) of the city, giving a total height between 168-173 m TAW.

So I took a lot of photos on clear, low turbulence days in that direction but mostly found nothing or sporadically something very blurred and difficult to identify. In addition the position on my photographs differed a quarter degree with the Zuidertoren on Google maps. So I wasn’t sure. But I found additional clues because I could recognize something that looked like the top of the green dome of the Koekelberg Basilica, which is one of the biggest churches in the world. I could recognize the upper part of the main dome and the smaller dome on top of it. That church in the Brussels suburb Ganshoren, at 62.3 km, is 100 m high but on a 55 m – 60 m hill, giving a total height of 155 m to 160 m TAW. I found the angle with the possible (blurred) Zuidertoren on my photograph exactly matched with Google Maps, although the position once again was a quarter degree wrong compared to nearby objects. This top is only very faintly visible on this pano but one will have a better look on my coming ‘discovery’ pano.

But it are the photographs of this panorama, recorded on September 7, 2018 that allowed me to identify the ‘Zuidertoren’ with absolute certainty. I was able to capture the reflection of direct orange sunlight on the northwestern glass wall, which horizontally, only happens minutes before sunset. This means one has to be in the right direction at the right time. This condition happens during two short periods per year. Given my position in relation to the Zuidertoren, April 13-15 and August 28-29 are optimal. But I didn't know a few weeks ago. So it was a bit of a coincidence I caught the reflection on Sept 7 which was still quite intense because I could even see it with naked eyes.
So by determining the angle of reflection and comparing the apparent angle of the reflective surface (the northwestern wall) I obtained an absolute proof.

Conclusion: the Zuidertoren, Tour du Midi, the highest tower in Brussels (and in Belgium), at 65.8 km, is the farthest object seen from Waterfront so far. I don’t expect to find something at a greater distance until two 200 m+ towers in Rotterdam are finished.

Right of the green Water tower of Axel, a few 70 m hills in Flemish Brabant are visible too such as Kravaalbos/Terrenberg and Kartelobos at distances of about 50 to 52 km.

My sorry for deleting the riddle, which I think would remain unsolved. Jörg Nitz suggested correctly a building in Brussels.
But I copied the comments.

Canon Eos M6 with EF-M 18-150 mm, 3 p RAW, 150 mm (240 mm KB), iso 100, f 8, 1/50 s, PTGuiPro, 10580x3665 156.3 MB TIFF, crop h=1815, downsized>1000>500 TIFF>sharpening>2930x500 977KB JPEG


I realize that Netherlands, with its average altitude, is not the ideal country to take panos ;-)
But, seriously, I really appreciate your attempts.
2018/09/13 20:47 , Giuseppe Marzulli
Dear Giuseppe, maybe you would feel annoyed in flat NL and B. One of the big problems is that long distance shots low to the surface often are heavily blurred.
2018/09/13 21:25 , Mentor Depret
I think it is necessary to understand the difficulty of making certain panos and evaluating them accordingly.
2018/09/13 21:40 , Giuseppe Marzulli
@Mentor, your more accurate and consequential report on the discovery of the visibility of Zuidertoren has captivated me from the beginning to the end. Together with the rarely successful images of the panorama, this should be the proof of visibility.
But the influence of the curvature of the earth should still be considered and the refraction must be estimated.
2018/09/13 23:21 , Heinz Höra
@Heinz, I haven't done these corrections and I should first study how to calculate. Do you think the tower isn't visible in a straight line?
2018/09/13 23:50 , Mentor Depret
@Mentor, I have checked it out and found that the curvature does not affect the visibility of the high buildings of Brussels. The view radius of waterfront is only 31 km, but that of Zuidertoren is 51 km. So together they are larger than 66 km. This theoretical value only says that the highest point of Zuidertoren should be visible if there are no surveys in between.
2018/09/14 11:16 , Heinz Höra
@Heinz, yes that is the theoretical maximal distance. To have an idea how much height of the Zuidertoren we can see, I did following calculation. I estimate the height of the horizon at about 25 m TAW (5 m terrain + 20 m trees). I lowered the height of my camera (66 m NAP=68 m TAW) and Zuidertoren with 25 m to 43 m and 145 m respectively. This results into a theoretical distance of 66.4 km or almost exactly the distance between the two. So this means we see about 25 m of the top.
2018/09/14 12:14 , Mentor Depret
@Heinz, I found an interesting pano from the highest globe of the Atomium (I estimate 143 m TAW, maybe 152 m if really from the top platform), showing the southwestern half of Brussels. At left one sees the Zuidertoren and a bit left of the middle, the green dome of the Koekelberg basilica. They are clearly the two highest objects which I can see.
2018/09/14 17:32 , Mentor Depret
Respect for your extensive investigation and this interesting documentation.
I am also often looking for far distant views from low location.
2018/09/14 17:48 , Friedemann Dittrich
@Mentor, I can not understand your calculation for the first time.
But I have calculated the elevation angle for Zuidertoren and the Koekelberg Basilica. These are respectively - 0.16 ° in normal refraction. BUT the elevation of Waasmunster cuestas with 32 m TAW + 20 m tall trees at 29 km distance is only - 0.14 °. However, this mean that the range of hills with such tall trees covered the two buildings!
If I do the refraction coefficient greater than 25% (normal value is 13.5%) the elevation angles of the buildings and of the wooded hill are approximately equal size (about -0.13°).
These are only approximate calculations, but they show that exceptionally good visibility conditions must prevail, so that you can see the two buildings in Brussels from your waterfront building.
2018/09/14 18:29 , Heinz Höra
@Heinz, but for the Basilica and Zuidertoren, you have not to take the cuesta into account because it ends at about 147°. The horizon in front of the Basilica and Zuidertoren is 5 m terrain plus 15-20 m trees, so 20 to 25 m TAW.

Concerning my calculation, I increased the zero level of the globe to +25 m to compensate for the horizon and then calculated the theoretical max distance. If this equals the real distance - which it does - the height seen should be 25 m.
2018/09/14 19:11 , Mentor Depret
thx Friedemann, very much appreciated and Heinz for your interesting insights and abundant comments.
2018/09/15 15:08 , Mentor Depret
I appreciate your efforts since I did the same in my area.
2018/09/16 13:37 , Steffen Minack

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