Line layer in Map, why did I end up with this weird format?

[daturpin]

Let me start by saying, I, via trial and error, answered my own question. Basically, I have a map in QlikSense Enterprise which shows the positions of ships on the ocean, and the positions of those ships are calculated by interpolation from a table with name, lat, long, and time, where each ship might have 1 or 1000 waypoints, and the calculated position comes from a slider.

Now, it took a lot of trial and error to get this to work in QlikSense, being that QlikSense doesn't natively do macros... Basically I got it to work using Vizlib and the ability of Vizlib to run script and conduct partial app reloads.

And, I thought, since I have that data, wouldn't it also be nice to show a line layer which draws out the paths of the ships over the entire timeline? So I did, but there is weirdness here that I can't quite explain.

So, in the Map, you can create a line layer, and the positional data can be either two fields, or one field with line geometry (or multi-line geometry) using a JSON standard. Sort of. By trial and error, I found this to be a simplified standard, where you format your line geometry as [[lat,lon],[lat,lon],[lat,lon]]. To build this format, I iteratively built the string by concatenating (&) the bits of this during runtime and writing to my table.

Weirdness #1: For some reason, the open square bracket works fine, but to create a close square bracket, I needed to use ']]' for each closed bracket. Why? Dunno, but basically it means the string I need to write is actually:

'[[lat,lon]],[lat,lon]],[lat,lon]]]]'

Weirdness #2: This is also a problem with Google Earth, where if you have a line cross the IDL it instead DRAWS A LINE COMPLETELY AROUND THE OTHER SIDE OF THE EARTH. Which is annoying. But by experimenting, I found that the solution is the same as Google Earth: If your longitude is negative, add 360. So -179 becomes 181, -1 becomes 359, etc. It works. Following are the before and after for a moving vessel:

In conclusion, this isn't a question per se, but if anyone can explain why the format of square brackets was so weird, I'd appreciate it. Otherwise I think it's helpful info for anyone making world maps with point and line layers. (fellow wargamers?)