[mkgmap-dev] Level and Resolution

Sun Jul 17 03:01:07 BST 2011

Roger Calvert <roger at rogercalvert.me.uk> writes:

> I have mapped 'barrier=gate' to an unused Garmin code using the instruction
>
> barrier=gate {add name = 'gate'} [0x1600 level 2]
>
> in the 'points' style file, with a corresponding entry defining a
> graphic in the TYP file.

Two separate points to understand:

  1) There is a list of about 6 zoomlevels in a style file, and really
  the format only stores those 6, so using levels not in the level list
  just truncates (or rather the next smaller number, I think.  This is
  probably not your problem.

> This works, except that it appears at all magnifications in MapSource,
> but only at very high resolution (scale = 120ft) in the GPS. Changing
> the 'level' or using 'resolution' instead seems to make no difference.
>
> I have a very similar problem with 'railway=rail'. Whatever the
> resolution in the 'lines' file, it appears all the time in MapSource,
> but only below 0.3 miles resolution in the GPS. But other lines -
> e.g. 'highway=track' appear much earlier, even when they have the same
> resolution or level.

  2) I'm very fuzzy on this, but it seems that for some objects garmin
  devices or programs will impose their own notion of smallest scale to
  display them, separately from what's specified.  I have heard of this
  with rail, not being rendered below the '300m' level (meaning at
  scales named by '500m' and larger distances).  I would not be
  surprised if a) gate were like rail and b) behavior is not consistent
  from model to model and receiver to mapsource.

So: you're not crazy; this really is a mess.
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