我有一些“道路”作为 sp 对象:
class : SpatialLinesDataFrame
features : 17360
extent : 490176.4, 567680.9, 148639.1, 212821 (xmin, xmax, ymin, ymax)
coord. ref. : +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
variables : 4
names : osm_id, lanes, type, width
min values : 73, 2, motorway, 6.3
max values : 587969162, 6, trunk, 18.9
我将它们转换为 sf 对象，如下所示:
roads <- st_as_sf(roads, crs = 27700)
转换后，SRID 为空，proj4string(可能)看起来不正确。为什么是这样？我可以修吗？
Simple feature collection with 17360 features and 4 fields
geometry type: LINESTRING
dimension: XY
bbox: xmin: 490176.4 ymin: 148639.1 xmax: 567680.9 ymax: 212821
epsg (SRID): NA
proj4string: +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717 +x_0=400000 +y_0=-100000 +ellps=airy +towgs84=446.448,-125.157,542.06,0.1502,0.247,0.8421,-20.4894 +units=m +no_defs
First 10 features:
osm_id lanes type width geometry
73 73 2 primary 6.3 LINESTRING (526256 191950, ...
74 74 2 primary 6.3 LINESTRING (525236.4 190755...
75 75 2 primary 6.3 LINESTRING (526324.4 192518...
79 79 2 primary 6.3 LINESTRING (524912.4 190235...
482 482 2 primary 6.3 LINESTRING (527283.9 198571...
546 546 2 primary 6.3 LINESTRING (506089.1 205091...
1210 1210 2 primary 6.3 LINESTRING (526023.9 195013...
1213 1213 2 primary 6.3 LINESTRING (524861.1 196243...
1214 1214 2 primary 6.3 LINESTRING (524482.3 196798...
1698 1698 2 primary 6.3 LINESTRING (527335.3 195524...
我想我需要解决这个问题，因为然后我想将我的数据 st_transform() 转换为与栅格相同的 CRS，我必须提取一些值。
crs(raster)
CRS arguments:
+proj=laea +lat_0=52 +lon_0=10 +x_0=4321000 +y_0=3210000 +ellps=GRS80 +units=m +no_defs
我想我可以通过做这样的事情将我的“道路”转换为正确的 CRS？但它不起作用。我得到....
roads <- st_transform(roads, crs(raster))
'Error: cannot create a crs from an object of class CRS
帮助表示赞赏。谢谢你。
最佳答案
你必须适应 st_transform 像这样的论点:
roads <- st_transform(roads, crs = 4326)
或者
roads <- st_transform(roads, crs = proj4string(raster))
或者正如@TimSalabim所说:
roads <- st_transform(roads, crs = crs(raster)@projargs)
或者正如@R'n'E 指出的那样:
roads <- st_transform(roads, crs = st_crs(raster))
关于r - 更改 SF 对象的 CRS，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/50372533/