wingkwong / geodesy

A Dart library for geodesic and trigonometric calculations working with points and paths

Geodesy

About

A Dart library for implementing geodesic and trigonometric calculations based on a spherical Earth model for working with points and paths such as distances, bearings and destinations.

How to Use Geodesy

Commands

For Dart

dart pub add geodesy

For Flutter

flutter pub add geodesy

Import Geodesy

import 'package:geodesy/geodesy.dart';

Class

The Geodesy class provides a collection of methods for performing various geodetic calculations, including distance calculations, point intersections, and more. This class is designed to work with geographical coordinates in the form of latitude and longitude.

Please see the Usage and Example.

Static Methods

Static methods are available without using Geodesy instance.

Please see the Usage and Example.

License

This project is licensed under MIT.

Contributors

Thank you for your contributions! We appreciate all the contributions from the community.

geodesy's Issues

Calculate the bounding box coordinates around a geo point (latitude and longitude)?

Hello,

Given a position on map (latitude and longitude) can this lib calculate a bounding box per distance? Eg give me a bounding box whose corners are a km away from the central position?

PS So we can avoid relying on Google Maps for bbox https://developers.google.com/android/reference/com/google/android/gms/maps/model/VisibleRegion

Enrich Class descriptions

add the missing descriptions for classes.

ref: https://pub.dev/documentation/geodesy/latest/geodesy/geodesy-library.html

Polygon envelope

Yet another feature request: I would like to be able to get a rectangular polygon that contains a given polygon: similar to the envelope method of GeoPandas.

This is to fit a map boundaries around a polygon, to center on a polygon. Code could be something like:

List<LatLng> rectangleBounds = geoEnvelope(<LatLng>[
  // coords
]);

error in calculatePolygonArea unit

In my cartographic app I have a tool to measure a distance and a surface with user selected points.
I've used Geoportail to check if measurment is correct (just measuring the same thing in my app and the website).
While distance using distanceBetweenTwoGeoPoints seems correct, area using calculatePolygonArea looks quite wrong.
When Geoportail says 0.116km², distanceBetweenTwoGeoPoints returns 0.00001370770505371155 m², which is not at all the same.
After a quick look at the code, maybe there is a unit mismatch ? You are summing & multiplying lat & lng values directly, which are not meters, and returning directly that value in supposely m².
Something looks wrong ?

EDIT : when looking at some other algo, they look very different, using more advanced math trigonometry ?
https://github.com/dartclub/turf_dart/blob/bbccfb3cebb532a2e8341294f30590ae8a541b5d/lib/src/area.dart#L74
https://github.com/divvitco/geodart/blob/be4016f1b74baf5dcf54fef7ce5e3ed00028ba0b/lib/src/featureTypes/geometries/linear_ring.dart#L43
https://github.com/kb0/maps_toolkit/blob/540da77cf12d2a1dfceb12183776fb4969020750/lib/src/spherical_util.dart#L186

EDIT: I've compared using computeArea of maps_toolkit, it work as expected.

Geopoint in polygon

Hi. I have seen there is a isGeoPointInBoudingBox function. I'm looking for a way to tell if a geopoint is in a given polygon.

Would a isGeoPointInPolygon function be doable?

Geofence geopoints located in a distance radius from a given geopoint

Hi. I am looking for a way to get a circular line around a geopoint calculated from a distance. Would it be doable?

[Edit]: more precisely what is needed is to find the geopoints located in a radius from a given geopoint, passing a list of geopoints to check

Polygon with hole

How to construct polygon with hole?

Polygons intersection

Any idea howa to get the intesection between the blue polygon and the grey one ? Thanks

Use the LatLong package?

Hi, would it be possible to use the LatLong(https://pub.dartlang.org/packages/latlong) package for standard coordinates data structure? It looks pretty solid (it enforces 90/-90 degrees constrains for latitude and longitude for example) and standard (it is used in great packages like Flutter map).

It could reduce duplicated maintenance work. Your module covers a much more broader scope it could makes sense to use it. And also to provide a standard data format across packages: example: I have a list of these coordinates and want to pass it to isGeoPointInPolygon: for now I have to convert it to use your class, which has an unpleasant cost.

Polygon centroid

Hi, I'm looking for a way to find the centroid of a polygon. I've seen the midPointBetweenTwoGeoPoints function. It would be useful to have a polygonCentroid function to have the center between multiple points.

{Edit]: rephrased for clarity

isGeoPointInBoundingBox

Hi there, thank you for the library. Here are few issues with isGeoPointInBoudingBox:

1. There is a mistake: missing n in isGeoPointInBou_n_dingBox.
2. It doesn't work: https://github.com/wingkwong/geodesy/blob/master/lib/src/geodesy.dart#L176-L184

You require topLeft and bottomRight points, but actually expect bottomLeft and topRight.

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Detected dependencies

pub

pubspec.yaml

• latlong2 ^0.9.0
• lints ^4.0.0
• test ^1.16.8
• dart >=3.0.0 <4.0.0

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Null Safety Upgrade

upgrade to be null safe. Switch from deprecated LatLong to LatLong2 package which is a forked null safe version that is not deprecated. Run dart migrate, update tests