The file was undesirably large (about 32 MB) which seemed to stem from the precision of the coordinates being up to 17 decimal places.
Fortunately, the simple yet powerful Notepad++ could help – by using the regex find and replace we can reduce the precision of the coordinates.
To do this,
- open the Replace dialogue (Ctrl + H)
- under ‘Search mode’ select ‘Regular expression’
- in ‘Find what’ enter the following
- leave ‘Replace with’ empty
This will reduce the precision down to 5 decimal places – change the 5 in step 4 for alternatives.
For me, this reduced the file from 32 MB to 15 MB – a massive saving that will result in a faster loading map.