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https://github.com/paulmach/orb
Types and utilities for working with 2d geometry in Golang
https://github.com/paulmach/orb
2d geo geojson geospatial gis mapbox-vector-tile wkb wkt
Last synced: about 14 hours ago
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Types and utilities for working with 2d geometry in Golang
- Host: GitHub
- URL: https://github.com/paulmach/orb
- Owner: paulmach
- License: mit
- Created: 2016-03-28T01:19:01.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2024-08-07T15:43:29.000Z (4 months ago)
- Last Synced: 2024-11-27T18:06:37.281Z (15 days ago)
- Topics: 2d, geo, geojson, geospatial, gis, mapbox-vector-tile, wkb, wkt
- Language: Go
- Homepage:
- Size: 1.44 MB
- Stars: 913
- Watchers: 21
- Forks: 104
- Open Issues: 17
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE.md
Awesome Lists containing this project
- awesome-go - orb - 2D geometry types with clipping, GeoJSON and Mapbox Vector Tile support. (Science and Data Analysis / HTTP Clients)
- zero-alloc-awesome-go - orb - 2D geometry types with clipping, GeoJSON and Mapbox Vector Tile support. (Science and Data Analysis / HTTP Clients)
- awesome-vector-tiles - orb - A Go geometry library with mvt <-> geojson support. (Parsers & Generators)
- awesome-go-extra - orb - 03-28T01:19:01Z|2022-05-16T17:39:19Z| (Science and Data Analysis / HTTP Clients)
- awesome-go-zh - orb
- awesome-go - orb - Types and utilities for working with 2d geometry in Golang - ★ 61 (Science and Data Analysis)
README
# orb [](https://github.com/paulmach/orb/actions?query=workflow%3ACI+event%3Apush) [](https://codecov.io/gh/paulmach/orb) [](https://goreportcard.com/report/github.com/paulmach/orb) [](https://pkg.go.dev/github.com/paulmach/orb)
Package `orb` defines a set of types for working with 2d geo and planar/projected geometric data in Golang.
There are a set of sub-packages that use these types to do interesting things.
They each provide their own README with extra info.
## Interesting features
- **Simple types** - allow for natural operations using the `make`, `append`, `len`, `[s:e]` builtins.
- **GeoJSON** - support as part of the [`geojson`](geojson) sub-package.
- **Mapbox Vector Tile** - encoding and decoding as part of the [`encoding/mvt`](encoding/mvt) sub-package.
- **Direct to type from DB query results** - by scanning WKB data directly into types.
- **Rich set of sub-packages** - including [`clipping`](clip), [`simplifing`](simplify), [`quadtree`](quadtree) and more.
## Type definitions
```go
type Point [2]float64
type MultiPoint []Point
type LineString []Point
type MultiLineString []LineString
type Ring LineString
type Polygon []Ring
type MultiPolygon []Polygon
type Collection []Geometry
type Bound struct { Min, Max Point }
```
Defining the types as slices allows them to be accessed in an idiomatic way
using Go's built-in functions such at `make`, `append`, `len`
and with slice notation like `[s:e]`. For example:
```go
ls := make(orb.LineString, 0, 100)
ls = append(ls, orb.Point{1, 1})
point := ls[0]
```
### Shared `Geometry` interface
All of the base types implement the `orb.Geometry` interface defined as:
```go
type Geometry interface {
GeoJSONType() string
Dimensions() int // e.g. 0d, 1d, 2d
Bound() Bound
}
```
This interface is accepted by functions in the sub-packages which then act on the
base types correctly. For example:
```go
l := clip.Geometry(bound, geom)
```
will use the appropriate clipping algorithm depending on if the input is 1d or 2d,
e.g. a `orb.LineString` or a `orb.Polygon`.
Only a few methods are defined directly on these type, for example `Clone`, `Equal`, `GeoJSONType`.
Other operation that depend on geo vs. planar contexts are defined in the respective sub-package.
For example:
- Computing the geo distance between two point:
```go
p1 := orb.Point{-72.796408, -45.407131}
p2 := orb.Point{-72.688541, -45.384987}
geo.Distance(p1, p2)
```
- Compute the planar area and centroid of a polygon:
```go
poly := orb.Polygon{...}
centroid, area := planar.CentroidArea(poly)
```
## GeoJSON
The [geojson](geojson) sub-package implements Marshalling and Unmarshalling of GeoJSON data.
Features are defined as:
```go
type Feature struct {
ID interface{} `json:"id,omitempty"`
Type string `json:"type"`
Geometry orb.Geometry `json:"geometry"`
Properties Properties `json:"properties"`
}
```
Defining the geometry as an `orb.Geometry` interface along with sub-package functions
accepting geometries allows them to work together to create easy to follow code.
For example, clipping all the geometries in a collection:
```go
fc, err := geojson.UnmarshalFeatureCollection(data)
for _, f := range fc {
f.Geometry = clip.Geometry(bound, f.Geometry)
}
```
The library supports third party "encoding/json" replacements
such [github.com/json-iterator/go](https://github.com/json-iterator/go).
See the [geojson](geojson) readme for more details.
The types also support BSON so they can be used directly when working with MongoDB.
## Mapbox Vector Tiles
The [encoding/mvt](encoding/mvt) sub-package implements Marshalling and
Unmarshalling [MVT](https://www.mapbox.com/vector-tiles/) data.
This package uses sets of `geojson.FeatureCollection` to define the layers,
keyed by the layer name. For example:
```go
collections := map[string]*geojson.FeatureCollection{}
// Convert to a layers object and project to tile coordinates.
layers := mvt.NewLayers(collections)
layers.ProjectToTile(maptile.New(x, y, z))
// In order to be used as source for MapboxGL geometries need to be clipped
// to max allowed extent. (uncomment next line)
// layers.Clip(mvt.MapboxGLDefaultExtentBound)
// Simplify the geometry now that it's in tile coordinate space.
layers.Simplify(simplify.DouglasPeucker(1.0))
// Depending on use-case remove empty geometry, those too small to be
// represented in this tile space.
// In this case lines shorter than 1, and areas smaller than 2.
layers.RemoveEmpty(1.0, 2.0)
// encoding using the Mapbox Vector Tile protobuf encoding.
data, err := mvt.Marshal(layers) // this data is NOT gzipped.
// Sometimes MVT data is stored and transfered gzip compressed. In that case:
data, err := mvt.MarshalGzipped(layers)
```
## Decoding WKB/EWKB from a database query
Geometries are usually returned from databases in WKB or EWKB format. The [encoding/ewkb](encoding/ewkb)
sub-package offers helpers to "scan" the data into the base types directly.
For example:
```go
db.Exec(
"INSERT INTO postgis_table (point_column) VALUES (ST_GeomFromEWKB(?))",
ewkb.Value(orb.Point{1, 2}, 4326),
)
row := db.QueryRow("SELECT ST_AsBinary(point_column) FROM postgis_table")
var p orb.Point
err := row.Scan(ewkb.Scanner(&p))
```
For more information see the readme in the [encoding/ewkb](encoding/ewkb) package.
## List of sub-package utilities
- [`clip`](clip) - clipping geometry to a bounding box
- [`encoding/mvt`](encoding/mvt) - encoded and decoding from [Mapbox Vector Tiles](https://www.mapbox.com/vector-tiles/)
- [`encoding/wkb`](encoding/wkb) - well-known binary as well as helpers to decode from the database queries
- [`encoding/ewkb`](encoding/ewkb) - extended well-known binary format that includes the SRID
- [`encoding/wkt`](encoding/wkt) - well-known text encoding
- [`geojson`](geojson) - working with geojson and the types in this package
- [`maptile`](maptile) - working with mercator map tiles and quadkeys
- [`project`](project) - project geometries between geo and planar contexts
- [`quadtree`](quadtree) - quadtree implementation using the types in this package
- [`resample`](resample) - resample points in a line string geometry
- [`simplify`](simplify) - linear geometry simplifications like Douglas-Peucker