```r
str(gps)
```

```
## Classes 'sf' and 'data.frame':	35 obs. of  5 variables:
##  $ name    : Factor w/ 11 levels "001","002","003",..: 1 2 3 4 5 6 7 8 9 1 ...
##  $ time    : POSIXct, format: "2019-10-30 11:35:43" "2019-10-30 11:55:18" ...
##  $ group   : Factor w/ 4 levels "A","B","C","D": 4 4 4 4 4 4 4 4 4 1 ...
##  $ geometry:sfc_POINT of length 35; first list element:  'XY' num  -2.04 50.69
##  $ site    : Factor w/ 2 levels "1","2": 1 1 1 1 1 1 2 2 2 1 ...
##  - attr(*, "sf_column")= chr "geometry"
##  - attr(*, "agr")= Factor w/ 3 levels "constant","aggregate",..: NA NA NA NA
##   ..- attr(*, "names")= chr  "name" "time" "group" "site"
```