Add sphere with radius equal to the semi-major axis of the WGS84 ellipsoid
Add the normal sphere
Add ol.Projection.getPointResolution
Implement getPointResolution for EPSG:3587
Implement getPointResolution for EPSG:4326
Estimate point resolution for Proj4js projections
Merge pull request #252 from twpayne/point-resolution

Point resolution
Add ScaleLine control
Add scale line control options to map options
Add scale line to examples