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Maplat Tin library

JavaScript library which performs homeomorphic conversion mutually between the coordinate systems of two planes based on the control points.
This is part of Maplat project.

Installation

node.js

The easiest way to install maplat_tin is with npm.

npm install @maplat/tin

Browser

Use maplat_tin.js

<script type="text/javascript" src="maplat_tin.js"></script>

How to use (node.js case)

var Tin = require('maplat_tin');

var tin = new Tin({
    wh: [500, 500],
    yaxisMode: Tin.YAXIS_FOLLOW
});

tin.setPoints([
  [[100,100], [200, 200]],
  [[200,200], [400, 400]],
  [[150,150], [320, 350]],
  [[200,100], [420, 220]]
]);
tin.updateTinAsync().then(function() {
  if (tin.strict_status == Tin.STATUS_STRICT) {
    console.log('Topology OK: In this case, roundtrip transform is guaranteed');
  } else if (tin.strict_status == Tin.STATUS_LOOSE) {
    console.log('Topology error: In this case, roundtrip transform is not guaranteed');
  } else {
    console.log('Something wrong');
  }

  //Forward transform
  var ord = tin.transform([160, 160], false);
  console.log(ord);
  //ord => [336.0769755832048, 360.048109739503]

  //Backward transform
  var rev = tin.transform(ord, true);
  console.log(rev);
  //rev => [160, 160]

  //Solving triangulated irregular network from many points by scrach takes too many time.
  //So, there are object-serialization method to store solved instance.

  var compiled = tin.getCompiled();

  var tin2 = new Tin();
  tin2.setCompiled(compiled);
  // Compiled triangulated irregular network was set. no "updateTinAsync" call is need.

  var ord2 = tin.transform([160, 160], false);
  console.log(ord2);
  var rev2 = tin.transform(ord2, true);
  console.log(rev2);
  //Same results with ord, rev
}).catch(function(e) {
  if (e == 'TOO LINEAR1' || e == 'TOO LINEAR2') {
    console.log('Given GCP points are too linear, fail to create triangulated irregular network.');
  } else {
    console.log('Something wrong');
  }
});

Options

wh (method: setWh)

Set width and height of the first coordinate system.
NOTE: If setWh was called, TIN network is reset. So need to call updateTinAsync() again.

yaxisMode

Set Tin.YAXIS_FOLLOW if the y coordinate of the first coordinate system is the same as the direction of the y axis of the second coordinate system, and set Tin.YAXIS_INVERT if it is in the opposite direction.
Default value is Tin.YAXIS_INVERT.

points (method: setPoints)

A set of corresponding points in the first coordinate system and the second coordinate system is specified as an array. Minimum 3 points required. Also, if the alignment of points is too linear, TIN can not be calculated at updateTinAsync and an error occurs.
NOTE: If setPoints was called, TIN network is reset. So need to call updateTinAsync() again.

Methods

updateTinAsync()

Return value is Promise. Calcurate TIN asynchronously. Before calling transform, this method needs to be completed.

transform(xy, inverse)

Convert the coordinates. If the value of inverse is false, the direction of conversion is from the first coordinate system to the second one, if it is true, the direction of conversion is reverse direction.

Properties

strict_status

Confirm after completion of updateTinAsync(). When the value is Tin.STATUS_STRICT, bijection conversion is guaranteed. In the case of Tin.STATUS_LOOSE it is not guaranteed.