无法使“平面”endcapStyle对R中的st_buffer起作用

9bfwbjaz 于 2023-04-09 发布在其他

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我目前正在使用纬度/经度坐标创建一个sfc行字符串表，并绘制一个缓冲区。然而，我无法让endcapstyle =“FLAT”参数工作。我希望这能工作，因为我需要缓冲区不延伸超过行的端点。我错过了什么？

library(sf)
library(mapview)
library(tidyverse)

## random coordinates for example
df_tbl <- tibble::tribble(
  ~lat,   ~lon,   ~lat2,   ~lon2,
  39.977917887303626, -105.28350982984472, 40.026678120413961, -105.20312377997453,
  39.934422269952776, -105.25986687400055, 39.902061443935025, -105.28605599432022)

## create points
beg_t <- df_tbl %>% select(lon, lat) %>% st_as_sf(coords = c("lon", "lat"), crs = 4326)  
end_t <- df_tbl %>% select(lon2, lat2) %>% st_as_sf(coords = c("lon2", "lat2"), crs = 4326)  

# combine start and end geometries
cbind(beg_t,end_t) -> points_ready 

# create linestrings

line_segments <- points_ready %>% 
  mutate(
    path = st_sfc(purrr::map2(
      .x = geometry, 
      .y = geometry.1, 
      .f = ~{st_union(c(.x, .y)) %>% st_cast("LINESTRING")}
    ),
    crs = 4326)) 

## try to use the FLAT endCapStyles
line_segments$buffer <- st_buffer(line_segments$path, dist = 2000, endCapStyle = "FLAT")
mapview(line_segments$path) + mapview(line_segments$buffer)  ## the buffers are not flat at the ends

r

来源：https://stackoverflow.com/questions/75952876/unable-to-get-flat-endcapstyle-to-work-for-st-buffer-in-r

1条答案

按热度按时间

jgovgodb1#

endCapStyle将仅在GEOS设置中工作=它与{s2}世界的球形操作不兼容。您可以完全关闭{s2}处理，或重新投影到平面CRS。
在下面的代码中，我使用了第二种方法，即Web Mercator（EPSG 3857）。
另外，我选择创建缓冲线作为一个单独的对象，因为点和线在WGS 84中，我不太喜欢在单个对象中混合CRS（{sf}的活动/非活动几何特性应该处理它，但它感觉不对）。

library(sf)
library(mapview)
library(tidyverse)

## random coordinates for example
df_tbl <- tibble::tribble(
  ~lat,   ~lon,   ~lat2,   ~lon2,
  39.977917887303626, -105.28350982984472, 40.026678120413961, -105.20312377997453,
  39.934422269952776, -105.25986687400055, 39.902061443935025, -105.28605599432022)

## create points
beg_t <- df_tbl %>% select(lon, lat) %>% st_as_sf(coords = c("lon", "lat"), crs = 4326)  
end_t <- df_tbl %>% select(lon2, lat2) %>% st_as_sf(coords = c("lon2", "lat2"), crs = 4326)  

# combine start and end geometries
cbind(beg_t,end_t) -> points_ready 

# create linestrings

line_segments <- points_ready %>% 
  mutate(
    path = st_sfc(purrr::map2(
      .x = geometry, 
      .y = geometry.1, 
      .f = ~{st_union(c(.x, .y)) %>% st_cast("LINESTRING")}
    ),
    crs = 4326)) 

## try to use the FLAT endCapStyles
buffered_lines <- line_segments$path %>% 
  st_transform("EPSG:3857") %>% # to force GEOS processing
  st_buffer(endCapStyle = "FLAT",
            dist = 2000)

mapview(line_segments$path) + mapview(buffered_lines)

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无法使“平面”endcapStyle对R中的st_buffer起作用

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