Wednesday, December 12, 2007

New Buffer Styles in JTS 1.9

JTS allows specifying styling parameters to control the appearance of generated buffer polygons.

End Cap styles have been available for a while. End caps can be Round (the default), Flat, or Square. For Round caps, the Quadrant Segments parameter controls the degree of approximation to a true circular arc.

End Cap Styles: Round, Flat, Square

JTS 1.9 adds the ability to specify the Join Style. The Join style controls how the offset curves for consecutive line segments are joined together. The Join type can be Round (the default), Mitre, or Bevel. If Mitre is specified, a further Mitre Limit parameter is provided to control how long mitred joins can be before they are beveled off. The maximum length of a mitred corner is equal to the Mitre Limit multiplied by the buffer distance.

Join Styles: Mitre (limit = 10), Mitre (limit = 1), Bevel

The JTS TestBuilder has been enhanced to allow specifying all of these parameters, so it can be used to experiment with the visual effects of the various styles.

Thursday, December 6, 2007

Hey What's That - Terrain Panoramas Mashup

Here's a nifty mashup using Google Maps. It computes a skyline terrain panorama from a given location.



The computed skyline isn't bad, although a bit optimistic (I'm pretty sure you can't see the Olympics from downtown Vancouver!). I think this particular query is ignoring earth curvature (although apparently you can choose to take it into account.)

The site uses it's own SRTM dataset. The gazetteer is impressive - not sure how they get that information.

Monday, December 3, 2007

Cross-Border issues with Google Maps terrain

So GM now has terrain - yay! But they seem to have short-changed half the continent. Check this screenshot from the border just south of Chilliwack. Notice the American Border Peak - but where's the Canadian one? And what's with that crazy-looking border swathe?


I assure US viewers that Canada isn't normally this blurry. And no, it isn't proof that we really do have a year-round 4 ft snowpack!

Ok, I know - never satisfied. Really, this is a very nice feature. I just hope Google gets their north-of-the-border vision lasered real soon...