# Jord - Geographical Position Calculations

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> __Jord__ [_Swedish_] is __Earth__ [_English_]

## What is this?

Jord is a [Haskell](https://www.haskell.org) library that implements various geographical position calculations using the algorithms described in [Gade, K. (2010). A Non-singular Horizontal Position Representation](http://www.navlab.net/Publications/A_Nonsingular_Horizontal_Position_Representation.pdf).

- Transformation between ECEF (earth-centred, earth-fixed), Latitude/Longitude and N-Vector positions for spherical and ellipsoidal earth model
- Transformation between Latitude/Longitude and N-Vector positions
- Local, Body and North, East, Down Frames: delta between positions, target position from reference position and delta
- surface distance, initial & final bearing, interpolated position, great circle intersections, cross track distance, ...

## How do I build it?

If you have [Stack](https://docs.haskellstack.org/en/stable/README/),
then:
```sh
$ stack build --test
```

## How do I use it?

[See documentation on Hackage](http://hackage.haskell.org/package/jord/docs/Data-Geo-Jord.html)

```haskell
import Data.Geo.Jord

-- Delta between positions in frameL
let p1 = decimalLatLongHeight 1 2 (metres (-3))
let p2 = decimalLatLongHeight 4 5 (metres (-6))
let w = decimalDegrees 5 -- wander azimuth
deltaBetween p1 p2 (frameL w) wgs84 -- = deltaMetres 359490.579 302818.523 17404.272

-- destination position from 531914N0014347W having travelled 500Nm on a heading of 96.0217°
-- using mean earth radius derived from the WG84 ellipsoid
destination (readLatLong "531914N0014347W") (decimalDegrees 96.0217) (nauticalMiles 500) r84

-- surface distance between 54°N,154°E and its antipodal position
-- using mean earth radius derived from the WG84 ellipsoid
let p = decimalLatLong 54 154
surfaceDistance p (antipode p) r84
```

Jord comes with a REPL (built with [haskeline](https://github.com/judah/haskeline)):

```sh
$ jord-exe
jord> finalBearing (destination (antipode 54°N,154°E) 54° 1000m) 54°N,154°E
jord> angle: 126°0'0.0" (126.0)
```