[mkgmap-dev] Documentation for the new Douglas-Peucker options in low-res-opt branch

Mon Jun 14 21:32:39 BST 2021

Hi Gerd,

I think the original documentation for --reduce-point-density and
--reduce-point-density-polygon could do with some improvement. It also seems
bizarre to have a recommended value that is not the default. Is 2.6 the
default if --reduce-point-density is specified without a value, or is it
also the default if the option is not specified? Are the units metres? Is
the distance the same no matter what resolution is used, or does the
distance increase at lower resolution? If the former, wouldn't it be better
to increase by a factor of 1.414 at successive resolutions? Would this be
sufficient to not need to be able to specify individual values for
resolutions?

I'm not keen on having two very differently named options that basically
achieve the same aim and suggest that it would be better to simply extend
the existing --reduce-point-density options with
--reduce-point-density=value|resolution:value[,...] or even better
--reduce-point-density=value[,...] where the first value applies to the
first used resolution and so on, with the last value being scaled for any
further resolutions that have not had a value specified. 

Is there a reason why polygons need different values than lines? Shouldn't
reduce-point-density-polygon default to the reduce-point-density value?

I note that although the documentation belongs to the low-res-branch, it is
showing up on the mkgmap command line web page.

Regards,
Mike

-----Original Message-----
From: Gerd Petermann [mailto:GPetermann_muenchen at hotmail.com] 
Sent: 14 June 2021 07:43
To: mkgmap-dev at lists.mkgmap.org.uk
Subject: [mkgmap-dev] Documentation for the new Douglas-Peucker options in
low-res-opt branch

Hi all,

I've now added documentation for these new options, see:
https://www.mkgmap.org.uk/websvn/diff.php?repname=mkgmap&path=%2Fbranches%2F
low-res-opt%2Fresources%2Fhelp%2Fen%2Foptions&rev=4775&peg=4775

Is it clear enough?
I think the recommend value --reduce-point-density-polygon=8 is far too high
at low resolutions. Should this be changed?

Together with the new --improve-overview option this branch version can
produce much better results for the lower resolutions.

Gerd