flightconflicts

commit 02dba5e675237d39b97c3f1697996b35615cfee1
parent 3d131a37c0cfdeec57f7d209208059c5d5ee33f3
Author: eamoncaddigan <eamon.caddigan@gmail.com>
Date:   Fri, 20 May 2016 11:47:24 -0400

First pass at flat-Earth code

Diffstat:
A
R/lonlatToXY.R
 | 
28
++++++++++++++++++++++++++++
A
man/lonlatToXY.Rd
 | 
27
+++++++++++++++++++++++++++

2 files changed, 55 insertions(+), 0 deletions(-)
diff --git a/R/lonlatToXY.R b/R/lonlatToXY.R
@@ -0,0 +1,28 @@
+#' Convert lon/lat coordinates to north/east coordinates (in feet) using a 
+#' flat-Earth approximation.
+#' 
+#' @param longitude A numeric vector.
+#' @param latitude A numeric vector.
+#' @param originLongintude The logntidue for which x = 0 feet.
+#' @param originLatitude The latitude for which x = 0 feet.
+#' @return A n x 2 matrix giving the x and y distance (respectively), in feet,
+#'   of each longitude/latitude pair from the origin longitude/latitude.
+lonlatToXY <- function(longitude, latitude, originLongitude, originLatitude) {
+  # This implementation is based on code from:
+  # http://williams.best.vwh.net/avform.htm#flat
+  dlon <- longitude - originLongitude
+  dlat <- latitude - originLatitude
+  
+  # Radius in feet and flattening based on WGS84
+  a <- 20925646
+  f <- 1/298.257223563
+  e2 <- f*(2-f)
+  
+  R1 <- a*(1-e2)/(1-e2*(sin(originLatitude))^2)^(3/2)
+  R2 <- a/sqrt(1-e2*(sin(originLatitude))^2)
+  
+  xDistance <- R2 * cos(originLatitude) * dlon
+  yDistance <- R1 * dlat
+  
+  return(cbind(xDistance, yDistance))
+}
diff --git a/man/lonlatToXY.Rd b/man/lonlatToXY.Rd
@@ -0,0 +1,27 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/lonlatToXY.R
+\name{lonlatToXY}
+\alias{lonlatToXY}
+\title{Convert lon/lat coordinates to north/east coordinates (in feet) using a 
+flat-Earth approximation.}
+\usage{
+lonlatToXY(longitude, latitude, originLongitude, originLatitude)
+}
+\arguments{
+\item{longitude}{A numeric vector.}
+
+\item{latitude}{A numeric vector.}
+
+\item{originLatitude}{The latitude for which x = 0 feet.}
+
+\item{originLongintude}{The logntidue for which x = 0 feet.}
+}
+\value{
+A n x 2 matrix giving the x and y distance (respectively), in feet,
+  of each longitude/latitude pair from the origin longitude/latitude.
+}
+\description{
+Convert lon/lat coordinates to north/east coordinates (in feet) using a 
+flat-Earth approximation.
+}
+