Wednesday, November 10, 2010

Duplicate OSM Features in UD Campus Map

I noticed a couple places where we have two polygons on top of each other (particularly for parking polygons) in the UD Campus Map. I just wanted to note, if you're trying to modify an existing polygon on the map, make sure that you're changing the existing shape, rather than adding a new one (otherwise we're loosing attributes on the exisiting shape).

Here are two screenshots to demonstrate what I'm talking about (note that only the second polygon retains attribute information/properties as listed in the right-hand sidebar), though it appears the first polygon was intended to replace the second.

I've fixed this problem by adding nodes to the second polygon (the original one that has attributes/properties) and dragging them to match the footprint of the first (new, intended to replace the first), and deleting that one.

Tuesday, November 9, 2010

Zoom to extent of new vector layer in OL

Zooming to the maximum extent of all features in a vector layer does not work unless all features have been loaded. Therefore it is necessary to register an event handler, as demonstrated below ('layer' is any object of class OpenLayers.Layer.Vector):'featuresadded', map,function(){this.zoomToExtent(layer.getDataExtent())});