ggplot2和地图：geom_point和annotation_raster位置不匹配

今天是个好日子，

使用下面的代码我可以使用以下命令成功地从 Google 检索栅格ggmap，绘制一个annotation_raster using ggplot2，并将站点位置绘制为栅格图层顶部的红点。在绘图上，位置不太匹配（它们应该沿着海岸线）。我知道我的网站的位置是正确的，因为当我将数据作为 KML 文件上传到 Google 地球时，它们会绘制出它们应该在的位置。

建议将不胜感激。

该代码将按原样运行...请注意，您需要一个开发版本ggplot2，可在 github 上找到。安装：

# install.packages("devtools")
library(devtools)
install_github("ggplot2")

对于代码：

library(ggplot2)
library(ggmap)
library(grDevices)
theme_set(theme_bw())

# Some coordinates of points to plot:
siteLat = c(-22.94414, -22.67119, -29.25241, -30.31181, -32.80670, -33.01054, -32.75833, -        33.36068, -31.81708, -32.09185, -32.31667, -34.13667, -34.05016, -33.91847, -34.13525, -34.12811, -34.10399, -34.16342, -34.41459, -34.58786, -34.83353, -34.37150, -34.40278, -34.17091, -34.08565, -34.04896, -33.98066, -34.02448, -34.20667, -34.05889, -33.97362, -33.99125, -33.28611, -33.02407, -33.01798, -32.99316, -31.09704, -31.05000, -30.91622, -30.70735, -30.28722, -30.27389, -29.86476, -29.54501, -29.49660, -29.28056, -28.80467, -27.42472)
siteLon = c(14.50175, 14.52134, 16.86710, 17.26951, 17.88522, 17.95063, 18.02778, 18.15731, 18.23065, 18.30262, 18.32222, 18.32674, 18.34971, 18.38217, 18.43592, 18.45077, 18.48364, 18.85908, 19.25493, 19.33971, 20.00439, 21.43518, 21.73972, 22.12749, 23.05532, 23.37925, 23.64567, 23.89933, 24.77944, 25.58889, 25.64724, 25.67788, 27.48889, 27.91626, 27.92182, 27.95036, 30.18395, 30.21666, 30.32982, 30.48474, 30.76026, 30.83556, 31.04479, 31.21662, 31.24665, 31.44403, 32.07567, 32.73333)
siteName = c(seq(1:length(siteLon)))
sites <- as.data.frame(cbind(siteLat, siteLon, siteName))

# specify raster's approximate coordinates:
lats = c(-35, -20)
lons = c(10, 35)

SAMap <- GetMap.bbox(lons, lats, maptype = "satellite")

# extract "real" coords of raster:
lonr <- c(SAMap$BBOX$ll[2], SAMap$BBOX$ur[2])
latr <- c(SAMap$BBOX$ll[1], SAMap$BBOX$ur[1])

# extract raster fill data:
h_raster <- as.raster(SAMap$myTile)

# plot using annotation_raster:
g <- ggplot(sites, aes(siteLon, siteLat))
g + annotation_raster(h_raster, lonr[1], lonr[2], latr[1], latr[2]) +
  geom_point(aes(x = siteLon, y = siteLat), colour = "red", data = sites) +
  scale_x_continuous(limits = lonr) +
  scale_y_continuous(limits = latr)

（抱歉，我无法发布图片，因为我是新来的）。

好的，多亏了 David Kahle，问题已经解决了。参见这篇文章：

AJ