[mkgmap-dev] address index question

Thu Nov 29 11:57:44 GMT 2012

Hi

> There's something else that I think is highly non-obvious to new people:
> there are a ton of options (no surprise), but the defaults are not
> really useful.  The norm among mkgmap users is to give a large number of
> options, but for some reason (perhaps trying to keep behavior
> consistent) these options are not default.   In the --remove-short-arcs
> case, I don't understand why anyone wouldn't want it.

I do agree that there are far too many options and I did start work
on dealing with this a while back. But I suspect that while everyone
might say that things are confusing there is not all that much
consensus on actually removing any option.

But I will try again, this time working in smaller chunks.

The very first thing is to implement (and it is done or mostly
done already) is to have --no-option versions of any option,
because without that we can't really change any defaults.

To start we should classify every option according to why it exists.
I'll suggest the following list of reasons to start with.

1. options that are basically --make-it-work (and 1b --make-it-fail!)
2. workarounds because the automatic algorithm fails in some cases.
3. matters of taste and style.
4. add information to the map (eg --family-id)
5. select what is created
6. control operations with a large performance impact (time or memory)
7. control warnings about the input osm file
8. modify the map (eg make cycleways)
9. obsolete options
10. supports some random thing that someone wanted to do once
11. selecting input files

The I think every option should have two questions asked of it:
- Why and when would you want to set this
- Why and when would you not want to set this
Then remove it or change the default as appropriate.

For several options I have no idea what the answers are.

> Another point is that you probably want --route in addition to --index.

Yes I agree.

> FWIW, here are the options I use that I suspect everyone should use (or
> mine are off from the consensus and I should change):

OK I will classify these by way of example and do the whole list in
the next few days.

>      --tdbfile \
Reason 5. I think it should be the default and option removed.

>      --reduce-point-density=4 \
>      --reduce-point-density-polygon=8 \
Reason 3. Although if 4 is really the recommended value it should be
the default value. Likewise 8 for polygons.

>      --merge-lines \
I think this is 1 and 2, (perhaps some of 6?). We should always merge
lines if we can without breaking anything, but I think the current way
isn't ideal doesn't always work? (not sure).

>      --route \
Probably should be default now.

>      --check-roundabouts \
R 1 (and 7?) just do it and remove option.

>      --check-roundabout-flares \
R-7?

>      --remove-short-arcs=6 \
Already defaulted and should be removed.

>      --adjust-turn-headings \
R 1 its just part of making routing work well?

>      --report-similar-arcs \
>      --report-dead-ends=2 \
R 7 should just be one warnings/report flag: 
--warnings=similar-arcs,dead-ends,etc

>      --add-pois-to-areas \
R 8. But could be considered to be just making it work in the Garmin
format. Are there any downsides?

>      --index \
5 and 6. I'd be inclined not to make it the default

..Steve