[Tagging] Bridges and layers

[Nathan Edgars II]

On Mon, Jul 26, 2010 at 7:59 PM, Dave F. <davefox at madasafish.com> wrote:
>  On 27/07/2010 00:28, Nathan Edgars II wrote:
>>
>> On Mon, Jul 26, 2010 at 8:45 AM, Dave F.<davefox at madasafish.com>  wrote:
>>>
>>>  On 26/07/2010 13:35, Nathan Edgars II wrote:
>>>>
>>>> On Mon, Jul 26, 2010 at 8:28 AM, Dave F.<davefox at madasafish.com>
>>>> wrote:
>>>>>
>>>>> Layer is used purely as an aid to the renderer to distinguish where two
>>>>> or
>>>>> more ways *cross* each other:
>>>>
>>>> Not quite purely - it gives nonredundant spatial information when a
>>>> bridge goes over another. Not that this has anything to do with the
>>>> layer_change proposal.
>>>
>>> "nonredundant spatial information"
>>>
>>> What's that when it's at home?
>>
>> Information about the relationship of two physical objects to each
>> other that isn't otherwise in the data.
>>
>> In other words, if you have two bridge=yes ways crossing without an
>> intersection node, that tells you nothing about which one is the
>> higher bridge. layer=* adds that information.
>
> That's what I meant. Maybe I should have said 'crosses over'

But it's not solely an aid to the renderer. Which bridge is higher is
a useful bit of data.