flightconflicts

commit 67059fc085cc432d0485dcbc3b3aca1208ab5fd8
parent 4ee3b6c94a29f814d2095fb5cd11667b2278cdd9
Author: eamoncaddigan <eamon.caddigan@gmail.com>
Date:   Fri, 20 May 2016 13:46:35 -0400

Fixed and passing tests.

Diffstat:
M
R/lonlatToXY.R
 | 
18
+++++++++++-------
A
tests/testthat/test_lonlatToXY.R
 | 
17
+++++++++++++++++

2 files changed, 28 insertions(+), 7 deletions(-)
diff --git a/R/lonlatToXY.R b/R/lonlatToXY.R
@@ -10,19 +10,23 @@
 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
+  lon0 <- originLongitude * pi / 180.0
+  lat0 <- originLatitude * pi / 180.0
+  
+  dlon <- longitude * pi / 180.0 - lon0
+  dlat <- latitude * pi / 180.0 - lat0
   
   # Radius in feet and flattening based on WGS84
   a <- 20925646
+  #a <- 6378137
   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)
+  R1 <- a*(1-e2)/(1-e2*(sin(lat0))^2)^(3/2)
+  R2 <- a/sqrt(1-e2*(sin(lat0))^2)
   
-  xDistance <- R2 * cos(originLatitude) * dlon
-  yDistance <- R1 * dlat
+  xyFeet <- cbind(R2 * cos(lat0) * dlon, 
+                  R1 * dlat)
   
-  return(cbind(xDistance, yDistance))
+  return(xyFeet)
 }
diff --git a/tests/testthat/test_lonlatToXY.R b/tests/testthat/test_lonlatToXY.R
@@ -0,0 +1,17 @@
+library(flightconflicts)
+context("lonlatToXY")
+
+test_that("Returns sensible values", {
+  kacyLon <- -74.5771667
+  kacyLat <- 39.4575833
+  # Find points 500 feet (152.4 m) from the origin
+  compassPoints <- geosphere::destPoint(c(kacyLon, kacyLat),
+                                        b = seq(0, 359, by = 45),
+                                        d = 152.4)
+  
+  xyFeet <- lonlatToXY(compassPoints[, 1], compassPoints[, 2], kacyLon, kacyLat)
+  
+  expect_equal(xyFeet[1, ], c(0, 500), tolerance = 1e-4)
+  expect_equal(xyFeet[3, ], c(500, 0), tolerance = 1e-4)
+  expect_equal(sqrt(apply(xyFeet^2, 1, sum)), rep(500, 8), tolerance = 1e-4)
+})