maths

Documentation

Overview

Package math contins generic math functions that we need for doing transforms. this package will augment the go math library.

Index

• Constants
• func AreaOfPolygon(p tegola.Polygon) (area float64)
• func AreaOfPolygonLineString(line tegola.LineString) (area float64)
• func DegToRad(deg float64) float64
• func DistOfLine(l tegola.LineString) (dist float64)
• func RadToDeg(rad float64) float64
• type Line
  • func (l Line) Clamp(pt Pt) (p Pt)
  • func (l Line) DistanceFromPoint(pt Pt) float64
  • func (l Line) ExInBetween(pt Pt) bool
  • func (l Line) InBetween(pt Pt) bool
  • func (l Line) SlopeIntercept() (m, b float64, defined bool)
• type Pointer
• type Pt
  • func DouglasPeucker(points []Pt, tolerence float64) []Pt
  • func Intersect(l1, l2 Line) (pt Pt, ok bool)
  • func (pt Pt) Coords() []float64
  • func (pt Pt) Delta(pt2 Pt) (d Pt)
  • func (pt *Pt) GoString() string
  • func (pt Pt) IsEqual(pt2 Pt) bool
  • func (pt Pt) String() string
  • func (pt Pt) Truncate() Pt
  • func (pt Pt) XCoord() float64
  • func (pt Pt) YCoord() float64
• type WindingOrder
  • func WindingOrderOf(sub []float64) WindingOrder
  • func WindingOrderOfLine(l tegola.LineString) WindingOrder
  • func (w WindingOrder) IsClockwise() bool
  • func (w WindingOrder) IsCounterClockwise() bool
  • func (w WindingOrder) Not() WindingOrder
  • func (w WindingOrder) String() string

Constants

const (
	WebMercator = tegola.WebMercator
	WGS84       = tegola.WGS84
	Deg2Rad     = math.Pi / 180
	Rad2Deg     = 180 / math.Pi
	PiDiv2      = math.Pi / 2.0
	PiDiv4      = math.Pi / 4.0
)

Functions

func AreaOfPolygon

func AreaOfPolygon(p tegola.Polygon) (area float64)

AreaOfPolygon will calculate the Area of a polygon using the surveyor's formula (https://en.wikipedia.org/wiki/Shoelace_formula)

func AreaOfPolygonLineString

func AreaOfPolygonLineString(line tegola.LineString) (area float64)

func DegToRad

func DegToRad(deg float64) float64

func DistOfLine

func DistOfLine(l tegola.LineString) (dist float64)

DistOfLine will calculate the Manhattan distance of a line.

func RadToDeg

func RadToDeg(rad float64) float64

Types

type Line

type Line [2]Pt

func (Line) Clamp

func (l Line) Clamp(pt Pt) (p Pt)

Clamp will return a point that is on the line based on pt. It will do this by restricting each of the coordiantes to the line.

func (Line) DistanceFromPoint

func (l Line) DistanceFromPoint(pt Pt) float64

DistanceFromPoint will return the perpendicular distance from the point.

func (Line) ExInBetween

func (l Line) ExInBetween(pt Pt) bool

func (Line) InBetween

func (l Line) InBetween(pt Pt) bool

InBetween will check to see if the given point lies the line provided inbetween the endpoints.

func (Line) SlopeIntercept

func (l Line) SlopeIntercept() (m, b float64, defined bool)

SlopeIntercept will find the slop (if there is one) and the intercept of the two provided lines. If there isn't a slope because the lines are verticle, the slopeDefined will be false.

type Pointer

type Pointer interface {
	Point() Pt
}

type Pt

type Pt struct {
	X float64 `json:"x"`
	Y float64 `json:"y"`
}

Pt describes a 2d Point.

func DouglasPeucker

func DouglasPeucker(points []Pt, tolerence float64) []Pt

func Intersect

func Intersect(l1, l2 Line) (pt Pt, ok bool)

Intersect find the intersection point (x,y) between two lines if there is one. Ok will be true if it found an intersection point, and false if it did not.

func (Pt) Coords

func (pt Pt) Coords() []float64

func (Pt) Delta

func (pt Pt) Delta(pt2 Pt) (d Pt)

func (*Pt) GoString

func (pt *Pt) GoString() string

func (Pt) IsEqual

func (pt Pt) IsEqual(pt2 Pt) bool

func (Pt) String

func (pt Pt) String() string

func (Pt) Truncate

func (pt Pt) Truncate() Pt

func (Pt) XCoord

func (pt Pt) XCoord() float64

func (Pt) YCoord

func (pt Pt) YCoord() float64

type WindingOrder

type WindingOrder uint8

WindingOrder the direction the line strings.

const (
	Clockwise WindingOrder
	CounterClockwise
)

func WindingOrderOf

func WindingOrderOf(sub []float64) WindingOrder

func WindingOrderOfLine

func WindingOrderOfLine(l tegola.LineString) WindingOrder

func (WindingOrder) IsClockwise

func (w WindingOrder) IsClockwise() bool

func (WindingOrder) IsCounterClockwise

func (w WindingOrder) IsCounterClockwise() bool

func (WindingOrder) Not

func (w WindingOrder) Not() WindingOrder

func (WindingOrder) String

func (w WindingOrder) String() string