我正在尝试将与蝙蝠位置(空间点数据帧)相关的数据叠加到科罗拉多州(空间多边形数据帧)。两个对象的 CRS 是不同的:
crs(colorado)
#CRS arguments:
# +proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0
crs(BatRange_data)
#CRS arguments:
# +proj=utm +zone=13 +datum=NAD83 +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0
当我重新投影蝙蝠数据时,CRS 确实发生了变化,但程度不受影响。
以前:
BatRange_data
#class : SpatialPointsDataFrame
#features : 2456
#extent : 139996.3, 748812, 4094998, 4535103 (xmin, xmax, ymin, ymax)
#coord. ref. : +proj=utm +zone=13 +datum=NAD83 +units=m +no_defs +ellps=GRS80 +towgs84=0,0,0
#variables : 17
后:
geo_proj = "+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"
crs(BatRange_data) = geo_proj
BatRange_trnsfrmd = spTransform(BatRange_data,geo_proj)
BatRange_trnsfrmd
#class : SpatialPointsDataFrame
#features : 2456
#extent : 139996.3, 748812, 4094998, 4535103 (xmin, xmax, ymin, ymax)
#coord. ref. : +proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0
#variables : 17
我无法在多边形上绘制点,因为我的多边形对象的范围与点对象的范围不同:
colorado
#class : SpatialPolygonsDataFrame
#features : 1
#extent : -109.0608, -102.042, 36.99223, 41.00561 (xmin, xmax, ymin, ymax)
#coord. ref. : +proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0
#variables : 13
为什么空间点数据帧的范围在重新投影和转换时没有变化?
可重现的示例(我自己测试了这个,并将其发送给朋友;它可以通过提供的内容重现):
#Libraries
x = c('raster','sp','rgdal')
# If you don't know if you've installed the packages for some of these
# libraries, run this:
# install.packages(x)
lapply(x, library, character.only=TRUE)
rm(x)
# Read in and format data -------------------------------------------------
BatRange_data = new("SpatialPoints", coords = structure(c(179935.719907205, 179935.938979813, 179935.938979813, 176598.335967664, 176598.335967664, 4499963.43180688, 4499963.30060606, 4499963.30060606, 4489332.4211975, 4489332.4211975), .Dim = c(5L, 2L), .Dimnames = list(NULL, c("coords.x1", "coords.x2"))), bbox = structure(c(176598.335967664, 4489332.4211975, 179935.938979813, 4499963.43180688), .Dim = c(2L, 2L), .Dimnames = list(c("coords.x1", "coords.x2"), c("min", "max"))) , proj4string = new("CRS" , projargs = NA_character_))
#Use state bounds from gadm website:
us = getData("GADM", country="USA", level=1)
#Extract states (need to uppercase everything)
co = "Colorado"
colorado = us[match(toupper(co),toupper(us$NAME_1)),]
#Re-project bat data to 'longlat'
geo_proj =
"+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"
crs(BatRange_data) = geo_proj
BatRange_trnsfrmd =
spTransform(BatRange_data,geo_proj)
plot(BatRange_trnsfrmd)
plot(colorado,add=TRUE)
在你的代码中:
geo_proj = "+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"
crs(BatRange_data) = geo_proj
BatRange_trnsfrmd = spTransform(BatRange_data,geo_proj)
BatRange_trnsfrmd
在尝试重新投影之前,您正在覆盖BatRange_data
到纬度/经度的原始投影。 因此,spTransform
什么都不做,因为它试图从 epsg:4326 重新投影到 epsg:4326。这就是您的范围没有改变的原因。
因此,您可能应该删除此行:
crs(BatRange_data) = geo_proj
一切都应该工作。
呵呵。