wroge/wgs84

A zero-dependency Go package for coordinate transformations.

WGS84 - Coordinate Transformations

github.com/wroge/wgs84/v2

I am currently in the process of rewriting the package. Some things will change and some new features will be added. One of these features is the support of NTv2 grid transformations and other projections, such as Krovak. If you would like to help or have any comments, please report them in the issues.

Web Mercator

package main

import (
	"fmt"

	"github.com/wroge/wgs84/v2"
)

func main() {
	transform := wgs84.Transform(wgs84.EPSG(4326), wgs84.EPSG(3857)).Round(3)

	east, north, _ := transform(10, 50, 0)

	fmt.Println(east, north)
	// 1.113194908e+06 6.446275841e+06

	// echo 10 50 | cs2cs +init=epsg:4326 +to +init=epsg:3857 -d 3
	// 1113194.908     6446275.841
}

OSGB

package main

import (
	"fmt"

	"github.com/wroge/wgs84/v2"
)

func main() {
	transform := wgs84.Transform(wgs84.EPSG(4326), wgs84.EPSG(27700)).Round(3)

	east, north, h := transform(-2.25, 52.25, 0)

	fmt.Println(east, north, h)
	// 383029.296 261341.615 0

	// echo -2.25 52.25 | cs2cs +init=epsg:4326 +to +init=epsg:27700 -d 3
	// 383029.296 261341.615 0.000
}

wgs84's Issues

Could you add support for https://epsg.io/5514?

The title says it, I want to convert https://epsg.io/5514 to WGS84 and this library seemed promising, but it looks like it doesnt support it

transform result accuracy

Here's my code

type spheroid struct {
	a, fi float64
}

func (s spheroid) A() float64 {
	return s.a
}

func (s spheroid) Fi() float64 {
	return s.fi
}

func main() {
	test := wgs84.Datum{
		Spheroid: spheroid{
			a:  6378137,
			fi: 298.257222101,
		},
		Area: wgs84.AreaFunc(func(lon, lat float64) bool {
			if lon < 118.5 || lon > 121.5 || lat < 24.43 || lat > 53.33 {
				return false
			}
			return true
		}),
	}

	proj := test.TransverseMercator(120, 0, 1, 500000, 0)

	epsg := wgs84.EPSG()
	epsg.Add(4549, proj)

	transform := wgs84.Transform(epsg.Code(4549), wgs84.LonLat())
	f1, f2, f3 := transform(478077, 4025869, 0)
	fmt.Println(f1, f2, f3)

}

wkt for epsg:4549

PROJCS["CGCS2000 / 3-degree Gauss-Kruger CM 120E",
    GEOGCS["China Geodetic Coordinate System 2000",
        DATUM["China_2000",
            SPHEROID["CGCS2000",6378137,298.257222101,
                AUTHORITY["EPSG","1024"]],
            AUTHORITY["EPSG","1043"]],
        PRIMEM["Greenwich",0,
            AUTHORITY["EPSG","8901"]],
        UNIT["degree",0.0174532925199433,
            AUTHORITY["EPSG","9122"]],
        AUTHORITY["EPSG","4490"]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",0],
    PARAMETER["central_meridian",120],
    PARAMETER["scale_factor",1],
    PARAMETER["false_easting",500000],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]],
    AUTHORITY["EPSG","4549"]]

With my code I got result is [119.75572865201768, 36.36317346481494, -3.6767683923244476e-05]
But What I got form epsg.io was [119.7557287, 36.3631738], and from gdaltransform was [119.755728654111, 36.3631737608256, 0]

So I am wandering what makes these differences? Is there any problems?

Support for LV95/CH1903+/EPSG:2056

Hello

is there a way to add Hotine Oblique Mercator Azimuth Center projection?
It's used in Switzerland: https://epsg.io/2056

Here is a valid transformation example: https://epsg.io/transform#s_srs=2056&t_srs=4326&ops=1676&x=2717134.0000000&y=1261162.0000000

Thanks!
Alex

generating factories out of WKT v1 (geotools epsg.properties)

hi,

i'm toying with the idea of tapping into geotools wkt epsg.properties and script/generate transformation factories for each definition. or simply parse wkt1, not decided yet.

perhaps parameterize MGI -> helmert with parameters from TOWGS84 definitions.
and then instrument transverseMercator with PROPERTY values.

how do you see it, would it be working approach en mass? what would "area" function be then?

WIP v2

I would like to change the API a little. So this is my first draft for v2: https://github.com/wroge/wgs84/tree/v2

Anyone who is interested can take a look at it. I am open to criticism.

• no predefined CRS anymore, instead all CRS are available via EPSG code ( wgs84.EPSG(code) )
• removed safe functions (Unknown EPSG codes return ErrCodeNotFound)
• removed area interface (not really used by anyone!?)
• cleaned up the projections so that the variables have the same name as in the guidance notes: https://drive.tiny.cloud/1/4m326iu12oa8re9cjiadxonharclteqb4mumfxj71zsttwkx/d6ce146d-81c5-423b-8cdb-1b66e801e167
• added the Krovak projection and I will gradually add more projections from the guidence notes

go get github.com/wroge/wgs84/v2

geometric altitude to wgs84 altitude

Hi, I am very new to gis, but if I have lat, long, and a geometric altitude (above mean sea level), can I use this package to convert the geometric altitude to the wgs84 altitude?