SAP HANA, is CET time zone in the middle of Europe?

[Vitaliy-R]

The autumn is in the full swing here in Wrocław. Cold and rainy. But let me bring us back to one hot (like +34°C hot) summer day in Croatia. With my family we visited the Pag island that day. Going off the beaten path is my second nature, so I turned my car into some small gravel road.

A few kilometers later along the road there was one monument that caught my attention.



Upon closer inspection I found it was a monument marking 15° East meridian.

"What is so special about that meridian?" I though. The Wikipedia page gave me the answer: "[This] meridian is the central axis of Central European Time." And reading further that wiki: there are more marks like this one in Pag. Seems like every country on the path of that meridian has their own monument 🙂

Maybe you have read my previous blog SAP HANA, tell me where the center of Europe is and remember that Europe's midpoint is somewhere in Belarus. That finding was based on some open source maps data I used in SAP HANA to calculate a centroid of a shape of European continent.

So, how central is the "central axis of the Central European time"? This time I decided to measure a middle point between Europe's most West and most East points. Let's use the same SAP HANA data as the previous time. We have geospatial functions ST_Xmin() and ST_XMax() to get those values and to calculate the middle point.

SELECT CONTINENT, 

	(SHAPE.ST_XMax() + SHAPE.ST_XMin()) / 2 AS MidPointLongitude

FROM "TESTGEO"."continent"

WHERE CONTINENT = 'Europe'

Indeed, much closer to the 15° meridian, than the longitude of the centroid calculated in the previous blog.

So, what did SAP HANA assumed as the westernmost point of Europe? Ireland? Island? No. Azores Islands. Not that obvious (at least it was not to me).

Geologically speaking Azores are located on two tectonic plates. Monchique Islet (31° 16′ 30″ W) sits on the North American Plate, and Faial Island, (28° 50′ 00″ W) is the westernmost point of the Eurasian Plate above sea level. Which one did SAP HANA pick?

Well, SHAPE.ST_XMin() for CONTINENT = 'Europe'returns -31.289030075073242, or 31°17' 20.5"W. It returned the point even further West, but that's just the quality of the open data I downloaded and used for calculations.

Still, roughly we can calculate the Europe's middle point using this approach.

SELECT CONTINENT,

	(SHAPE.ST_XMax() + SHAPE.ST_XMin()) / 2 AS MidPointLongitude,

	(SHAPE.ST_YMax() + SHAPE.ST_YMin()) / 2 AS MidPointLatitude

FROM "TESTGEO"."continent"

WHERE CONTINENT = 'Europe'

Where is it on the map?



Are we the very first ones to discover the brand new middle point of Europe continent? Or are there some claimed midpoints nearby? You bet! There is a little village Mõnnuste at the Estonian island of Saaremaa claiming to be that midpoint as well: https://www.facebook.com/pg/visitsaaremaa/photos/?tab=album&album_id=1452096204813951

It is 3 degrees east from the point we just calculated. But then we just have found that the open data map we used was not that precise. So, maybe it is indeed Mõnnuste after all? You may need to visit it yourself to find it out. There is only one problem. It is not in the Central European time zone anymore 😛

Bonus content

Thank you for reading through this post all the way till this point. As a bonus let me show you how to use the same ST_Centroid() geospatial function from the previous blog to get the same point as above.

SELECT CONTINENT,

	SHAPE.ST_Envelope().ST_Centroid().ST_asWKT() as MidPointLonLat

FROM "TESTGEO"."continent"

WHERE CONTINENT = 'Europe'

How possible? Check the tutorials group Introduction to SAP HANA Spatial engine to find a hint.

---

And welcome to Central Europe!

-Vitaliy, aka @Sygyzmundovych