New module `@turf/shortest-path` #956

stebogit · 2017-09-21T08:16:40Z

/**
 * Returns the shortest {@link LineString|path} from {@link Point|start} to {@link Point|end} without colliding with
 * any {@link Feature} in {@link FeatureCollection<Polygon>| obstacles}
 *
 * @name shortestPath
 * @param {Geometry|Feature<Point>} start point
 * @param {Geometry|Feature<Point>} end point
 * @param {GeometryCollection|FeatureCollection<Polygon>} obstacles polygons
 * @param {Object} [options={}] optional parameters
 * @param {string} [options.units="kilometers"] can be degrees, radians, miles, kilometers, ...
 * @param {number} [options.resolution=100] distance between matrix points on which the path will be calculated
 * @returns {Feature<LineString>} shortest path between start and end
 * @example
 * var start = turf.point([-5, -6]);
 * var end = turf.point([9, -6]);
 * var obstacles = turf.featureCollection([turf.polygon([[0,-7],[5,-7],[5,-3],[0,-3],[0,-7]]));
 *
 * var path = shortestPath(start, end, obstacles);
 *
 * //addToMap
 * var addToMap = [start, end, obstacles, path];
 */
module.exports = function (start, end, obstacles, options) {

There is a lot of room for improvements, but what do you think of this first draft @DenisCarriere @rowanwins ? Any suggestion to improve speed and/or final result is more than welcome.

rowanwins · 2017-09-21T09:19:37Z

Hey @stebogit

There a bunch of known algorithms for this sort of thing. For example try googling "dijkstra's algorithm", I think this is a semi-famous one that might help. Might be easier and more robust to follow a known pattern.

DenisCarriere · 2017-09-22T03:08:43Z

👍 Love it! @stebogit 🎩 off to you for trying to implement this directly with only TurfJS modules.

@rowanwins There a bunch of known algorithms for this sort of thing.

Agreed, would be neat to have a comparable to see if @stebogit's implementation is faster & accurate to those other algorithms. I'm 👍 for any direction we decide to go to, as long as it's fast and accurate.

DenisCarriere · 2017-09-22T03:14:38Z

packages/turf-shortest-path/index.js

+    if (getType(start) !== 'Point') throw new Error('start must be Point');
+    if (!end) throw new Error('end point is required');
+    if (getType(end) !== 'Point') throw new Error('end must be Point');
+    if (!obstacles) throw new Error('obstacles collection is required');


Could we possibly have obstacles as an optional parameter? In case you want to use this module over an iterative process and maybe in some scenarios you would have 2 points with or without an obstacle, we could simply just return a lineString from both points (same as an empty featureCollection).

Yes! Great idea 👍

DenisCarriere · 2017-09-22T03:15:42Z

packages/turf-shortest-path/index.js

+    collection.features.push(start);
+    collection.features.push(end);
+
+    var box = bbox(scale(bboxPolygon(bbox(collection)), 1.15)); // extend 15%


Couldn't extend also be an optional parameter instead of hardcoded as 15%?

This in my mind was just to allow some space to allow the path around any object, like to avoid this (just a silly example):

I don't see any other use for this parameter.

Fair enough... that is a pretty silly scenario 😝

DenisCarriere · 2017-09-22T03:19:20Z

packages/turf-shortest-path/package-lock.json

@@ -0,0 +1,1981 @@
+{


I've recently just been removing/excluding the package-lock.json files, I'm not too sure if we should be having two lock files (yarn + npm).

I've added package-lock.json to the .gitignore, we could always add it back, but it seems like two lock files is a bit overkill (we only need to stick with one).

593cb91

DenisCarriere · 2017-09-22T03:20:49Z

packages/turf-shortest-path/package.json

+    "grid-to-matrix": "1.3.0",
+    "javascript-astar": "0.4.1",
+    "pathfinding": "0.4.18"
+  }


There's definitely missing some dependencies in the package.json, this is one of the reasons why the TravisCI tests will fail.

All this is absolutely "work-in-progress", I added the whole @turf/turf for convenience while developing.
Sorry, I should have titled this more clearly as "proposal" (like the label); I was just interested at this point in you suggestions and check with you if my approach was reasonably sound so far.

👍 Looks great to me so far! Was just trying to get the tests to pass

DenisCarriere

Really awesome! Looking forward to add more tests to this, overall this looks like a great library.

A few concerns I mentioned in the comments, but looks great to me! 👍

DenisCarriere · 2017-09-22T03:24:33Z

@stebogit Do you have an ESLint plugin installed in your current text editor?

TravisCI Error

/home/travis/build/Turfjs/turf/packages/turf-shortest-path/index.js
  116:37  error  'i' is defined but never used  no-unused-vars
✖ 1 problem (1 error, 0 warnings)

stebogit · 2017-09-22T04:11:21Z

@rowanwins thanks for the tip.
I did some quick research and it turns out A* is the best choice here, since it's faster and (as Dijkstra) is guaranteed to return the shortest path:
http://theory.stanford.edu/~amitp/GameProgramming/AStarComparison.html
Now, I'll try to compare the few implementations I found on npm to pick the best/fastest one.

Thanks guys!

rowanwins · 2017-09-22T04:21:08Z

good luck with it @stebogit ! I find it really hard reading some of those maths/computer science papers and interpreting what they're saying, but if we can follow them they should lead us to decent performant implementations, and I think they teach us some good skills in queues and sweeplines etc that we should be able to apply elsewhere.

DenisCarriere · 2017-09-23T04:26:29Z

A * looks like a great approach, @stebogit good luck in your npm quest to find one!

I like this image:

DenisCarriere · 2017-09-23T04:29:45Z

@stebogit Other possible module name would be @turf/least-cost-path, however I still prefer your original proposed name @turf/shortest-path.

bulutkartal · 2017-09-26T18:21:55Z

I don't know if you guys would consider but shortest sea routes may be killer, either with reverse altitude or based on depth colors on maps. here is an example based on color.

rowanwins · 2017-09-26T23:46:34Z

Hi @bulutkartal

Are you able to elaborate on your idea, are you saying that altitude or depth have a bearing on the path calculation? This module is for the actual calculation of the shortest path, it doesn't take into account how to visualise the result.

bulutkartal · 2017-09-27T00:00:31Z

I was trying to mean the reserve altitude can be used to calculate shortest sea routes(only water based), but using elevation services may be quite expensive and I don't think it is very suitable for turf. But instead of elevation services , map background colors can be used to calculate shortest sea routes. Lines will not pass through the land, only will stay in water colors. The link I sent above as an example works that way. It calculates the shortest distance between two ports and the line script creates stays in water. I saw the approach when I opened their bundled js. It was kinda cool what they did. This wouldn't be beneficial for land routes. I just saw the example was created at sea and idea just came out and found that link :)

rowanwins · 2017-09-27T02:02:03Z

Hi @bulutkartal

Using the proposed module you will be able to pass in your start and end point (presumably ports), as well as a bunch of polygons (which represent land borders), the output line will show you the route between the points avoiding the land. So it wont have anything to do with elevation. I hope that helps clear things up.

stebogit · 2017-09-27T07:04:48Z

Just a quick note, I'm not really sure this implementation is the best one, 'cause the path should not move only on a grid...
I believe the right output should look more like this (compared to the one above):

I'll keep looking for an alternative though, probably after we are done with v5.0.

bulutkartal · 2017-09-27T15:10:36Z

using elevation was just an another idea to prevent line going through land since elevation will be negative in water. Was just an idea, nothing more :) But using colors are easier and faster approach.

DenisCarriere · 2017-09-27T17:53:48Z

I believe the right output should look more like this

@stebogit Agreed, the 2nd map looks like it would be a better solution.

👍 to push this at the next minor release v5.1, big push for now would be to implement the ES Modules (we can add more modules afterwards).

DenisCarriere · 2017-10-25T20:58:38Z

🎉 Merged & Published @turf/shortest-path

stebogit added 4 commits September 18, 2017 01:36

initial commit

cadbc9a

completes implementation

237e2f3

implements first working solution; adds simple test

9da4abb

adds JSDoc example

63e3df5

stebogit added new-module proposal labels Sep 21, 2017

stebogit self-assigned this Sep 21, 2017

DenisCarriere reviewed Sep 22, 2017

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DenisCarriere approved these changes Sep 22, 2017

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stebogit changed the title ~~New module @turf/shortest-path~~ New module @turf/shortest-path (work-in-progress) Sep 22, 2017

stebogit added 2 commits September 24, 2017 23:35

simplified process => 3x faster;

4decbfb

adds alternative astar library, cleanes code

d1270ec

DenisCarriere changed the title ~~New module @turf/shortest-path (work-in-progress)~~ New module @turf/shortest-path (⚠️ Work in progress %80) Sep 25, 2017

DenisCarriere added 2 commits September 25, 2017 20:19

Merge branch 'master' into shortest-path

53fc5c7

Merge branch 'master' into shortest-path

1a0c147

DenisCarriere added this to the 5.1.0 milestone Sep 27, 2017

DenisCarriere added 8 commits October 25, 2017 10:28

Merge branch 'master' into shortest-path

59b9c22

Embed javascript-astar.js to repo

bc070d3

Update readme

a56decb

Add shortest-path to @Turf

d344607

Update distance with new options param

3eb32e8

Add shortestPath to index.js

813b726

Fix JSDoc example

670b957

Convert obstacles as optional parameters

439e9c2

DenisCarriere mentioned this pull request Oct 25, 2017

New module @turf/shortestPath #788

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DenisCarriere added 2 commits October 25, 2017 16:20

Add minDistance as optional parameters (NOT implemented yet)

c72d0c3

Add @turf/meta

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DenisCarriere changed the title ~~New module @turf/shortest-path (⚠️ Work in progress %80)~~ New module @turf/shortest-path Oct 25, 2017

DenisCarriere merged commit 74a30ab into master Oct 25, 2017

DenisCarriere deleted the shortest-path branch October 25, 2017 21:00

DenisCarriere modified the milestones: 5.1.0, 5.0.0 Oct 25, 2017

DenisCarriere mentioned this pull request Oct 25, 2017

@turf/shortest-path used for maritime industry #1040

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DenisCarriere mentioned this pull request Nov 9, 2017

New major release! Turf 5.0 🎉 #1082

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stebogit mentioned this pull request Jan 4, 2018

@turf/shortest-path is not giving the shortest path & minDistance option is not working #1211

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New module `@turf/shortest-path` #956

New module `@turf/shortest-path` #956

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New module @turf/shortest-path #956

New module @turf/shortest-path #956

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New module `@turf/shortest-path` #956

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