坐标混淆st_crop
Coordinate confusion with st_crop
我想裁剪 sf 对象。当我在 ggplot 中绘制对象时,我估计了我希望裁剪的区域。但是,当我使用 st_crop
执行裁剪时,tibble 有零行。这是为什么?
从 here 下载 alberta_border.RDS
library("sf")
library("ggplot2")
alberta <- readRDS("alberta_border.RDS")
ggplot() +
geom_sf(data = alberta) +
coord_sf()
alberta_crop <- st_crop(alberta, c(xmin = -118, xmax = -112, ymin = 50, ymax = 56))
alberta_crop
看来你打错了crs
。你可以告诉alberta shapefile的crs:
st_crs(alberta)
#Coordinate Reference System:
#EPSG: 26911
#proj4string: "+proj=utm +zone=11 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs"
您的输入文件使用的是 EPSG 26911
或 UTM zone 11N,而您输入的坐标 (c(xmin = -118, xmax = -112, ymin = 50, ymax = 56)
) 看起来是 lat/lng 或 EPSG 4326
.
因此我们应该在裁剪之前将原始数据集转换为lat/lng:
library(dplyr)
library(sf)
library(ggplot2)
alberta <- alberta %>%
st_transform(4326)
alberta_crop <- st_crop(alberta, c(xmin = -118, xmax = -112, ymin = 50, ymax = 56))
ggplot() +
geom_sf(data = alberta, aes(fill = 'alberta')) +
geom_sf(data = alberta_crop, aes(fill = 'cropped')) +
theme_minimal()
我想裁剪 sf 对象。当我在 ggplot 中绘制对象时,我估计了我希望裁剪的区域。但是,当我使用 st_crop
执行裁剪时,tibble 有零行。这是为什么?
从 here 下载 alberta_border.RDS
library("sf")
library("ggplot2")
alberta <- readRDS("alberta_border.RDS")
ggplot() +
geom_sf(data = alberta) +
coord_sf()
alberta_crop <- st_crop(alberta, c(xmin = -118, xmax = -112, ymin = 50, ymax = 56))
alberta_crop
看来你打错了crs
。你可以告诉alberta shapefile的crs:
st_crs(alberta)
#Coordinate Reference System:
#EPSG: 26911
#proj4string: "+proj=utm +zone=11 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs"
您的输入文件使用的是 EPSG 26911
或 UTM zone 11N,而您输入的坐标 (c(xmin = -118, xmax = -112, ymin = 50, ymax = 56)
) 看起来是 lat/lng 或 EPSG 4326
.
因此我们应该在裁剪之前将原始数据集转换为lat/lng:
library(dplyr)
library(sf)
library(ggplot2)
alberta <- alberta %>%
st_transform(4326)
alberta_crop <- st_crop(alberta, c(xmin = -118, xmax = -112, ymin = 50, ymax = 56))
ggplot() +
geom_sf(data = alberta, aes(fill = 'alberta')) +
geom_sf(data = alberta_crop, aes(fill = 'cropped')) +
theme_minimal()