r-在给定纬度和经度的情况下，如何提取海平面以上的海拔高度

Question

我正试图在数据中提取一组给定纬度和经度的海拔数据。我试着查找一些旧的答案(9-10年前(。。但是许多方法已经过时或者功能不起作用。有什么新的建议吗？

lat <- c(45.08323,40.08323)
long <- c(-82.46797,-81.46797)
df <- data.frame(lat, long)

我尝试了以下建议：

1. 使用geonames包，并从srtm3数字高程模型中获取值

我遇到错误，上面写着：Error in url(url, open = "r") : cannot open the connection to 'http://api.geonames.org/srtm3JSON?lat=NA&lng=NA&

2. 我试着按照链接答案中的建议使用googleway和Elevater pacakages

对于最新的R>4.0版本。

I get an error that says   Configuration failed because libudunits2.so was not found. Try installing:
* deb: libudunits2-dev (Debian, Ubuntu, ...)
* rpm: udunits2-devel (Fedora, EPEL, ...)
* brew: udunits (OSX)
If udunits2 is already installed in a non-standard location, use:
--configure-args='--with-udunits2-lib=/usr/local/lib'
if the library was not found, and/or:
--configure-args='--with-udunits2-include=/usr/include/udunits2'
if the header was not found, replacing paths with appropriate values.
You can alternatively set UDUNITS2_INCLUDE and UDUNITS2_LIBS manually. 

当我尝试安装所需的软件包时：

"包"libudunits2"不可用于此版本的R"；

###编辑：什么有效？

library(geonames)
readLines(url("http://api.geonames.org/",open="r"))
options(geonamesUsername= "MyUsername") #Note you have to create a username one the website AND enable webservices on your geonames user account at https://www.geonames.org/manageaccount. 
GNsrtm3(54.481084,-3.220625)

Answer 1

这样可以获得第二个点，但不能获得第一个点。

library(elevatr)
library(rgdal)
lat <- c(45.08323,40.08323)
long <- c(-82.46797,-81.46797)
df <- data.frame(long, lat)
get_elev_point(df, prj="EPSG:4326")
# Note: Elevation units are in &units=Meters 
# Note:. The coordinate reference system is:
#  GEOGCRS["WGS 84 (with axis order normalized for visualization)",
#     DATUM["World Geodetic System 1984",
#         ELLIPSOID["WGS 84",6378137,298.257223563,
#             LENGTHUNIT["metre",1]]],
#     PRIMEM["Greenwich",0,
#         ANGLEUNIT["degree",0.0174532925199433]],
#     CS[ellipsoidal,2],
#         AXIS["geodetic longitude (Lon)",east,
#             ORDER[1],
#             ANGLEUNIT["degree",0.0174532925199433,
#                 ID["EPSG",9122]]],
#         AXIS["geodetic latitude (Lat)",north,
#             ORDER[2],
#             ANGLEUNIT["degree",0.0174532925199433,
#                 ID["EPSG",9122]]]]
#             coordinates elevation elev_units
# 1 (-82.46797, 45.08323)        NA     meters
# 2 (-81.46797, 40.08323)    271.82     meters

Answer 2

需要创建用户名并在https://www.geonames.org/manageaccount

library(geonames)
readLines(url("http://api.geonames.org/",open="r"))
options(geonamesUsername= "MyUsername") #Note you have to create a username one the website AND enable webservices on your geonames user account at https://www.geonames.org/manageaccount. 

GNsrtm3(54.481084,-3.220625)