2地点間の標高

Google APIを利用して、2地点間を結ぶ直線の標高を取得

library(rjson)
library(RCurl)

## Loading required package: bitops

住所ベクトルからを緯度経度を取得する関数

get.coords <- function(addresses) {
    # Google APIで住所からJSONを取得
    get.url <- function(address) {
        address <- curlEscape(iconv(address, to = "UTF-8"))
        url <- paste("http://maps.googleapis.com/maps/api/geocode/json?address=", 
            address, "&sensor=false&region=JP&language=ja", sep = "")
        getURL(url)
    }
    # JSONから緯度経度を抽出
    get.coord <- function(json) {
        lat = fromJSON(json)$results[[1]]$geometry$location$lat
        lon = fromJSON(json)$results[[1]]$geometry$location$lng
        c(latitude = lat, longitude = lon)
    }
    # 上の2つの関数を住所ベクトルに適用
    jsons <- sapply(addresses, get.url)
    t(sapply(jsons, get.coord))
}

住所ベクトルから緯度経度を取得

addresses <- c("広島県広島市南区宇品東1-1-71", "広島県東広島市鏡山1-3-1")
coords <- get.coords(addresses)
coords

##                              latitude longitude
## 広島県広島市南区宇品東1-1-71    34.37     132.5
## 広島県東広島市鏡山1-3-1         34.40     132.7

2地点を結ぶ直線の標高を取得

n.sample <- 10
path <- paste(paste(coords[1, ], collapse = ","), paste(coords[2, ], collapse = ","), 
    sep = "|")

url <- paste("http://maps.googleapis.com/maps/api/elevation/json?", "path=", 
    path, "&samples=", n.sample, "&sensor=false", sep = "")

rjson <- fromJSON(getURL(url))

ext.path <- function(x) {
    ele = rjson$results[[x]]$elevation
    lat = rjson$results[[x]]$location$lat
    lon = rjson$results[[x]]$location$lng
    c(elevation = ele, latitude = lat, longitude = lon)
}

coords <- t(sapply(1:n.sample, ext.path))
coords

##       elevation latitude longitude
##  [1,]     2.774    34.37     132.5
##  [2,]    19.552    34.37     132.5
##  [3,]     7.001    34.37     132.5
##  [4,]    11.973    34.38     132.6
##  [5,]   347.773    34.38     132.6
##  [6,]   490.916    34.39     132.6
##  [7,]   319.536    34.39     132.6
##  [8,]   276.481    34.40     132.7
##  [9,]   230.736    34.40     132.7
## [10,]   231.137    34.40     132.7