[OSM-talk] How inaccurate was the mapnik distance/scale marker?
davefox at madasafish.com
Wed Feb 24 12:58:01 GMT 2010
Thanks for your replies
Egil Hjelmeland wrote:
> I assume you are referring to the OpenLayers based slippy map at
> openstreetmap.org? The Openlayers 2.8 ScaleLine class has the the
> problem that it does not handle that the map-scale is not constant
> accoss the map. The slippy map uses mercators projection, where the
> scale increases with 1/cos(lattiude). So the scaleline is correct at
> equator, but a over factor 2 off where I am at 62 north.
Excuse my ignorance, are you saying that it's 2x inaccurate at all zoom
> But it is trivial to make a mercator-specific variant of ScaleLine. I
> have made one here:
> http://www.egil-hjelmeland.no/kart/mercatorScaleLine.js. Anyone are free
> to use it. View it in action at my playground:
> http://www.egil-hjelmeland.no/kart/ .
So one of the mapnik guys could implement it quite easily then?
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