transform MULTILINESTRINGs to curves in cartodb

Question

I have a table with a column that contains MULTILINESTRINGs, where every string contains the longitude and latitude of a starting- and an end point, e.g.:

MULTILINESTRING((97.0253024 4.3685491,8.5618685 47.4524688))

Now I want to add geometry to those lines and make them curved so that I get an "arc" between the starting- and end point when I map them. What I have tried is the following:

UPDATE table_name SET the_geom = ST_Transform(ST_GeomFromText(column_with_multilinestrings, 4326), 953027)

Shouldn't this change the reference system from 4326 to 953027? It somehow doesn't work for me, I only get the following error:

Geometry SRID (953027) does not match column SRID (4326).

I already checked this post and the links in it. I also had a look at the cartodb tutorial for making curved lines, but everything I have seen so far concentrates on making curved lines/arcs from a centre point to other points (i.e. A -> B, A -> C, A -> D, etc.). The problem I have, is that I don't know how to draw those arcs from A -> B, C -> D, E -> F, etc.

What am I doing wrong? How can I transform these multilines to curved lines (i.e. arcs)?

John's comment on what ST_Segmentize actually does (and that everything gets converted back to 4326), led to the following SQL statement working to convert the MULTILINESTRINGs (in the_geom) to curved lines:

UPDATE table_name SET the_geom = (SELECT ST_Transform( ST_Segmentize( ST_Transform(table_name.the_geom, 953027),100000),4326))

Answer 1

In CartoDB, when you upload data, it must be in lat/lon, 4326, and this gets stored in a column called the_geom. An invisible column (in the GUI, at least) is also created called the_geom_webmercator, 3857, and this is what is actually used to display data, as all of the in-built wmts backdrops are in this projection.

In the CartoDB tutorial you reference, you will note that there is an outer call to ST_Transform that sets the resulting geometry back to 4326 that is used for the update, while the spatial reference 953207, which I believe is in meters -- actually I can find no reference to it in http://spatialreference.org/ -- is used inside the query as part of ST_Segmentize, which is the function that actually does the work of creating your nice curved (Multi)Linestrings, by breaking up the line into equal segment lengths (in the input SRID), which then appear curved when plotted on Web Mercator.