[OSM-dev] Coastline generalization tool and data

[Sandor Seres]

There is an explicate invitation to comment the tool and the results in
the paper so, I take the liberty to do so and post some of the many
potential comments.

-That some thin, or small, area objects/portions spontaneously disappear
when zooming out (scaling down) is natural and as a rule a quality
requirement in digital mapping. If there is a readability problem that
means that the display/rendering is using a wrong zoom level or the zoom
levels are not properly created. Whether we draw the area borders or not
is here irrelevant.

-Moving objects or parts of objects from their exact/correct geo-locations
is inacceptable in cartography. Even if this action provides "better
readability" it lifts out the corresponding map from cartography and moves
it to the illustrations area. Besides the fact that moving border segments
inwards (more inside) in some neighboring areas provides better visibility
of tiny water stripes, on tiny land stripes it has a contra effect. The
action brakes, or even removes these thin land stripes.

-The spline approximation of sharp turns/fine details in a raster-area
contour results in noticeably larger area fractions. This fact is known
from the times when raster-to-vector (parametric) presentation
transformation was a topic issue

-The data maintenance procedure might be tedious (if possible at all) for
low scale factor values (or higher zoom levels in the OSM semantics, like
level 9, 10 . 16 and so on). The planet_land raster images for these scale
factors, even with some bad/low resolution, might be extraordinary large.
For example the size of a 1:250 000 scale 512 dpi raster map of Norway (in
a conic projection) is 81 000 pixels * 101 000 pixels (the corresponding
Real World  resolution is around 30m). 

-For the same data size other models may provide radically richer content,
better edge quality and precision.

In my opinion, it is hard to believe that this tool/technology may compete
with other similar technologies for creating zoom-levels in digital
cartography. Yet, it may be of certain value in the field of illustrations
among many other options.

For more details and examples please visit

https://docs.google.com/file/d/0B6qGm3k2qWHqTEhfN2k2QldIQWs/edit?usp=shari
ng

Sandor.   

 

 

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