[Qgis-user] Creating Singleparts from Multiparts: Lines are being cut when self intersecting

[mvr at posteo.de]

Hello everyone,

for an analysis of bird movements, I need to count every line within a 
vector grid.

I have a line layer (with self-intersecting lines) and a vector grid. 
Now I want to count the lines in each raster. First I split the lines by 
intersecting the line layer with the vector grid.

Second, I need to do a multipart to singlepart for the lines because I 
want to count each line for each grid individually.

Now here is the problem: The lines are intersecting itself and at every 
intersection, the multipart-to-singlepart tool makes new parts of the 
lines. If I then count the lines within a grid, the result is too high 
because of the parts of the same line which were counted.

How can I avoid this, are there other workarounds?

(Question already at stackexchange.com : 
https://gis.stackexchange.com/questions/258004/qgis-lines-multipart-to-singlepart-without-splitting-at-self-intersection)

Thanks for help!

Martin