locate-m

locate-m(Line, Measure, Dimension_Name)

Locates a feature along a line by using measures (eg. timestamp) stored as an additional property ("dimension") of the line. The "dimension" must follow Mapbox's geojson-coordinateProperties proposal (https://github.com/mapbox/geojson-coordinate-properties). Similar to LocateFeaturesAlongRoutes in ArcGIS, but one measure at a time.

Use Cases

• Locating pictures along a GPX track (X, Y, Z, timestamp) using a "Date and Time" EXIF field.
• Locating incidents along a pipeline or road by using an arbitrary measure system.

Parameters

parameter	type	description
Line	LineString
Measure	Number	the measure at which to place the resulting feature
Dimension_Name	String	name of a property ("dimension") in properties/coordinateProperties

Example

  var locate_m = require('./');

  var line = {
      "type": "Feature",
      "geometry": {
          "type": "LineString",
          "coordinates": [
              [0, 0],
              [30, 0],
              [60, 30]
          ]
      },
      "properties": {
          "coordinateProperties": {
              // this is one dimension...
              "measures": [
                  0,
                  10,
                  20
              ]
          }
      }
  };

  var result = locate_m(line, 15, 'measures');

  // {
  //        type: 'Feature',
  //        geometry: {
  //            type: 'Point',
  //            coordinates: [ 45, 15 ]
  //        },
  //        properties: {
  //            locate_measure: 15
  //        }
  // }

Returns Feature.<Point>. Measure is also returned in Feature.properties.locate_measure.

Returns null if measure is smaller or larger than measures at start or end of line.

Throws an Exception if dimension is not present in coordinateProperties, or if measures are not increasing from vertex to vertex.

Tests

$ npm test