[OSM-newbies] Boundaries and Roads

Sun Apr 8 20:51:36 BST 2012

Well,
 from a GIS-persons point of view, you alway should avoid gaps in your map  
( = in your data).
Cartographic work is always generalizing the world, and only because you  
COULD go into detail in the sub-meter sphere technically with the digital  
means nowadays, you should should ask yourself: what is it good for?

So, what would be the information you provide, leaving a blank space  
between a field and a road?
Actually none, cause you do not specify what this gap is, although its  
quite clear that it's something between the road and the field.
But when its already obvious that there are strips of surface which do not  
belong neither to roads nor fields, you could right away leave them out  
and align the border of the field directly to the road.

In digitizing you normally decide about the map scale of the end product.  
With OSM-maps, thats a little bit difficult, cause there is no common  
sense about the usage, and therefor also about the production-scale.

The planned scale is important, cause it decides about the precision you  
need to get a satisfying result.
E.g. when you want to have a map in 1:5000, you normally digitize your  
features at a scale of 1:2500 or 1:2000.
The human eye can not distinguish features smaller than half a millimeter  
on a screen or on paper.

With a map in 1:5000, 1/2mm on screen is 2,5 meters in reality. Thats the  
planned "error" you are "allowed" to produce, cause on the planned scale,  
you can't even see it.

So the question should always be: what is the planned usage and what is  
the benefit from increasing the accuracy?

A field border outside a village is much less interesting than borders and  
features in a town center.
When the mapped part is mostly relevant for navigating, so as a real  
street map, you could easily set your planned scale to 1:25000 or even  
higher (with the resulting need for generalization), as normal users will  
watch it in that scale anyway to get the overview they need.
If it's a feature of high interest, you could set your planned scale to  
1:1000 or lower, with a resulting need of higher accuracy.

Hope that helped a bit.
Bernd

(please be aware: this opinion might be in conflict with some holy  
OSM-rules set up by some OSM-priests i do not know and do not care about.  
This is just cartographic common sense)

Am 08.04.2012, 13:00 Uhr, schrieb <newbies-request at openstreetmap.org>:

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> 1. Re: Boundaries and Roads (Dudley Ibbett)
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 7 Apr 2012 18:24:26 +0000
> From: Dudley Ibbett <dudleyibbett at hotmail.com>
> To: <newbies at openstreetmap.org>
> Subject: Re: [OSM-newbies] Boundaries and Roads
> Message-ID: <DUB112-W12202309E750B82C5746631C6310 at phx.gbl>
> Content-Type: text/plain; charset="iso-8859-1"
>
>
> Hi
>
> I could do with some advice on joining field boundaries to roads. Ihave  
> been doing this as the mapping style I am use to never has thefield  
> boundary running along the side the road. If the field boundaryalong the  
> road is well set back then I would consider drawing it howeverin most  
> cases it is within a few meters of the road and sometimes thereis not  
> gap at all. I believe the OSM application can in theory go downto 3m.  
> Drawing a field boundary along a road where the gap is less than3 meters  
> between the boundary (wall,fence) and the end of the road wouldtherefore  
> seem unrealistic.
>
> Should I try and draw the field boundary along the road in allsituations  
> or only do this when there is a large gap > 3m?
>
> If I don't draw the field boundary along the road should I link to the 
> road or should I stop the boundary just short of the road?
>
> Some guidance would be appreciated as I don't want to link boundaries to 
> roads if this could cause problems.
>
> Many thanks in advance.
>
> Regards
>
> Dudley
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