line-interpolate-points

line interpolate points

A Node module that interpolates the coordinates of any number of equidistant points along a line composed of one or more line segments, at an optional offset. It's particularly useful for GIS applications, and is analogous to the PostGIS ST_LineInterpolatePoint() and Python Shapely's shapely.geometry.LineString.interpolate(). Here's an example of points interpolated over different multi-segment lines (the second group has been offset):

the api

The module exports a single function, interpolateLineRange( ctrlPoints, number, offsetDist ).

• ctrlPoints is an array of 2D point arrays, like [ [ 5, 10 ], [ 7, 10 ], [ 14, 13 ] ]
• number is the number of points to interpolate (the endpoints included)
• offsetDist is an optional distance to move each interpolated point from its container line segment.
• minGap is an optional minimum distance to maintain between subsequent interpolated points (offsetDist is not taken into account here, as spacing between points is measured along the LineString). May decrease number if the gap between neighbors with that number of points would be lower than minGap.

> var interpolateLineRange = require( 'line-interpolate-points' )
> interpolateLineRange( [ [ 3, 10 ], [ 4, 10 ] ], 2 )
[ [ 3, 10 ], [ 4, 10 ] ]
> interpolateLineRange( [ [ 3, 10 ], [ 4, 10 ] ], 4 )
[ [ 3, 10 ],
  [ 3.3333333333333335, 10 ],
  [ 3.666666666666667, 10 ],
  [ 4, 10 ] ]
> interpolateLineRange( [ [ 4, 4 ], [ 4, 10 ], [ 7, 17 ] ], 6, 1 )
[ [ 3, 4 ],
  [ 3, 6.723154621172782 ],
  [ 3, 9.446309242345563 ],
  [ 3.9354486533919397, 12.387971226535829 ],
  [ 5.008151811686941, 14.890945262557498 ],
  [ 6.080854969981942, 17.393919298579167 ] ]

Install Dev Dependencies

$ npm install

Contributing

Please fork and pull request against upstream master on a feature branch. Please provide unit tests and script fixtures in the test directory.

Running Unit Tests

$ npm test

Continuous Integration

Travis tests every release against node version 0.10