使用 sf 和 sp 在 R 中的投影差异

Question

我有一个已从 GeoTIFF 转换为 shapefile 的网格。我想将 shapefile 转换并导出为 GeoPackage 并更改投影，以便它在 GIS 中打开时使用英国国家网格作为地理坐标系。然而，这似乎只适用于 sp 而不是 sf （它似乎没有保留像数据这样的方面）。

这是一个问题，因为我想导出包含多个图层的 GeoPackage，您目前只能在 sf 而不是 sp 中执行。我做错了什么吗？

library(rgdal)
library(sf)

download.file("https://drive.google.com/uc?id=1URbux7Sw25KFTySqRFKXk53DV2UK4lsA&export=download" , destfile="Grid_Shapefile.zip")
unzip("Grid_Shapefile.zip")
Grid_sp <- readOGR(".", "Grid_Shapefile")
Grid_sf <- st_as_sf(Grid_sp)

BNG_Grid_sp <- spTransform(Grid_sp, CRS("+init=epsg:27700"))
BNG_Grid_sf_v1 <- st_transform(Grid_sf, crs=27700)
BNG_Grid_sf_v2 <- st_transform(Grid_sf, crs="+init=epsg:27700 +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +datum=OSGB36 +units=m +no_defs +ellps=airy +towgs84=446.448,-125.157,542.060,0.1502,0.2470,0.8421,-20.4894")

BNG_Grid_sf_v1_geom <- st_geometry(BNG_Grid_sf_v1)
BNG_Grid_sf_v2_geom <- st_geometry(BNG_Grid_sf_v2)

proj4string(BNG_Grid_sp)
attributes(BNG_Grid_sf_v1_geom)
attributes(BNG_Grid_sf_v2_geom)

writeOGR(BNG_Grid_sp, dsn = "BNG_Grid_sp.gpkg", layer = "Grid_sp", driver = "GPKG")
st_write(BNG_Grid_sf_v1, "BNG_Grid_sf_v1.gpkg", "Grid_sf_v1")
st_write(BNG_Grid_sf_v2, "BNG_Grid_sf_v2.gpkg", "Grid_sf_v2")

Answer 1

使用ogrinfo，特别是命令

ogrinfo BNG*v1.gpkg Grid_sf_v1 > info1
ogrinfo BNG*v2.gpkg Grid_sf_v1 > info2

两个 info[1|2] 文件之间的差异，除了明显的 _v1 _v2 命名之外，还有：

13c13
<             TOWGS84[446.448,-125.157,542.06,0.15,0.247,0.842,-20.489]],
---
>             TOWGS84[446.448,-125.157,542.06,0.1502,0.247,0.8421,-20.4894]],

_v2 中的额外数字是否导致您在 ArcGIS 中遇到问题？

Answer 2

请在 https://github.com/r-spatial/sf/issues/810 上跟进，而不是在这里。

Answer 3

这个问题的解决方案（感谢 Roger posted here）是使用 lwgeom 包来完成 transformation.The post Roger on the sf GitHub 提供了更多细节。

library(rgdal)
library(sf)

download.file("https://drive.google.com/uc?id=1URbux7Sw25KFTySqRFKXk53DV2UK4lsA&export=download" , destfile="Grid_Shapefile.zip")
unzip("Grid_Shapefile.zip")
Grid_sp <- readOGR(".", "Grid_Shapefile")
Grid_sf <- st_as_sf(Grid_sp)

library(lwgeom)
BNG_Grid_sf_v4 <- st_transform_proj(Grid_sf, crs="+init=epsg:27700 +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +datum=OSGB36 +units=m +no_defs +ellps=airy +towgs84=446.448,-125.157,542.060,0.1502,0.2470,0.8421,-20.4894")
st_crs(BNG_Grid_sf_v4)
st_write(BNG_Grid_sf_v4, "BNG_Grid_sf_v4.gpkg", "Grid_sf_v4")

使用 sf 和 sp 在 R 中的投影差异

Projection differences in R using sf and sp

r

projection

coordinate-systems

sp

sf