When retrieving a number of data-points, but the kind of coordinate reference system (CRS) is not provided/known (for any reason), the `inborutils::guess_crs`

function plots the data for different projections on a map to make comparison possible. The main function is `guess_crs`

which creates the map with different options. The `transform_coordinates`

function can be useful as well, as it supports conversion and transformation of coordinate columns in a `data.frame`

.

This function only tries a selection of CRS commonly used in Belgium. We refer the user to the `crsuggest`

package which has a function by the same name `crsuggest::guess_crs`

, but is more generally applicable.

The aim is to quickly check the coordinate system by plotting the coordinates on a leaflet map with a list of given coordinate systems.

In order to run the functionalities, some R packags need to be installed. The set of required libraries is handled by the `inborutils`

package itself.

Loading the functionality can be done by loading the `inborutils`

package:

The `guess_crs`

function requires as minimal inputs:

- a
`data.frame`

- the x (longitude) column name
- the y (latitude) column name.

For example:

```
# my_dataframe has the columns "longitude" and "latitude"
guess_crs(coordinate_example, "longitude", "latitude")
```

```
## Warning in transform_coordinates(df, col_x, col_y, st_crs(prj), st_crs(4326)):
## Input CRS equal to output CRS No transform performed.
```

Furthermore, the optional argument `belgium`

is a boolean value (TRUE/FALSE) defining if the data is expectd to be in Belgium. Finally, the `epsg`

codes of the corresponding coordinate systems to check can be customised.

By default, the following CRS-systems are tested:

`EPSG:4326`

`EPSG:31370`

`EPSG:28992`

`EPSG:32631`

`EPSG:3812`

`EPSG:3035`

Which can be overridden by adapting the `projections`

argument:

```
guess_crs(coordinate_example, "longitude", "latitude", belgium = TRUE,
crs_try = c("EPSG:2000", "EPSG:2805", "EPSG:4326"))
```

```
## Warning in transform_coordinates(df, col_x, col_y, st_crs(prj), st_crs(4326)):
## Input CRS equal to output CRS No transform performed.
```

Check the spatial reference for the available codes.