如何将X和Y坐标转换为纬度和经度？

Question

以下是我拥有的数据框的示例，该数据框是从可公开获取的圣路易斯犯罪数据集中获得的。与数据相关的文档指出Xcoord和Ycoord位于[State Plane North America Datum 1983（NAD83）格式

   CodedMonth                                    Description   XCoord    YCoord
1:    2019-09        AUTO THEFT-PERM RETNT/UNRECOV OVER 48HR 908297.3 1018623.0
2:    2019-09        ASSLT-AGGRAV-OTH-WPN-2ND-CHILD-DOMESTIC 903995.7 1014255.0
3:    2019-09 FORGERY-ISSUING FALSE INSTRUMENT OR CERTIFICAT      0.0       0.0
4:    2019-09           STLG BY DECEIT/IDENTITY THEFT REPORT 890704.7 1010659.0
5:    2019-09          STALKING (HARASSMENT ONLY, NO THREAT) 881105.8 1008297.0
6:    2019-09               LARCENY-MTR VEH PARTS UNDER $500 882929.6  992941.3

如何将它们转换为Xcoord和Ycoord列为lon和lat格式，以便可以使用ggmap进行绘制

我找到了几个答案Convert latitude/longitude to state plane coordinates

但是我似乎无法使其用于我的数据

Answer 1

您可以使用sf库将其转换为简单的要素地理。为了使它起作用，您需要知道使用的坐标系，并根据提供的描述（国家平面NAD83，位于圣路易斯附近），我猜EPSG 26996（NAD83 /密苏里州东部USFT）是一个很好的起点。您可以在spatialreference.org处查找投影。更改为crs = ESRI：102696，因为第一个猜测无效。

library(sf)
# assuming your data is an object called my_df
my_sf_df <- st_as_sf(my_df, coords = c("XCoord", "YCoord"), crs = 102696) # 26996 didn't plot right

这会将x和y设置为空间坐标。您需要重新投影到WGS84这样的地理系统中，才能转换为纬度，您可以使用st_transform

my_latlon_df <- st_transform(my_sf_df, crs = 4326 ) %>%
      mutate( lat= st_coordinates(my_latlon_df)[,1],
              lon = st_coordinates(my_latlon_df)[,2])
my_latlon_df

# Simple feature collection with 6 features and 5 fields
# geometry type:  POINT
# dimension:      XY
# bbox:           xmin: -93.26566 ymin: 35.80151 xmax: -90.19163 ymax: 38.63065
# epsg (SRID):    4326
# proj4string:    +proj=longlat +datum=WGS84 +no_defs
# # A tibble: 6 x 6
# X1    CodedMonth Description                                                geometry   lat   lon
# * <chr> <chr>      <chr>                                                   <POINT [°]> <dbl> <dbl>
#       1 1:    2019-09    AUTO THEFT-PERM RETNT/UNRECOV OVER 48HR        (-90.19163 38.63065) -82.2  44.7
# 2 2:    2019-09    ASSLT-AGGRAV-OTH-WPN-2ND-CHILD-DOMESTIC         (-90.20674 38.6187) -82.3  44.7
# 3 3:    2019-09    FORGERY-ISSUING FALSE INSTRUMENT OR CERTIFICAT (-93.26566 35.80151) -93.3  35.8
# 4 4:    2019-09    STLG BY DECEIT/IDENTITY THEFT REPORT           (-90.25329 38.60893) -82.4  44.6
# 5 5:    2019-09    STALKING (HARASSMENT ONLY, NO THREAT)           (-90.2869 38.60251) -82.5  44.6
# 6 6:    2019-09    LARCENY-MTR VEH PARTS UNDER $500               (-90.28065 38.56034) -82.5  44.5

box <- st_bbox(my_latlon_df)
names(box) <- NULL 
base_map <- get_map(location = box, zoom = 7)

ggmap(base_map)+
      geom_sf(data = my_latlon_df,
              aes(color = CodedMonth)
              )

似乎没有坐标的点引起了问题，您需要确定如何处理。也想绕点]

# let's exclude point 3 for now

my_latlon_df <- my_latlon_df[c(1:2, 4:6),]
box <- st_bbox(my_latlon_df) # bounding box
names(box) <- NULL # removing non-complient labels
box2 <- box + c(-.2, -.2, .2, .2) # buffering
base_map <- get_map(location = box2, source = "osm")  # getting base map

ggmap(base_map)+
      geom_sf(data = my_latlon_df,
              aes(color = CodedMonth)
              )+
      scale_x_continuous(limits = c(-90.3, -90.1))+
      scale_y_continuous(limits = c(38.5, 38.7))