Paikkatietoikkuna's coordinate transformation service can be used to transform or convert coordinates between two different geodetic coordinate reference systems, or CRS (Input CRS -> Output CRS). Coordinate operations can be performed between CRSs that are based on the same datum (coordinate conversion) or between CRSs that are based on different datums (coordinate transformation). The coordinate transformation service supports the geodetic datums KKJ and EUREF-FIN and the vertical coordinate reference systems N43, N60 and N2000.

Coordinate transformations between KKJ and EUREF-FIN use a TIN-based (triangulated irregular network) affine transformation that considers deformations in KKJ. Coordinate transformations between the vertical coordinate reference systems N43, N60 and N2000 use a TIN-based linear interpolation from transfer corrections at vertices of triangles. Coordinate transformations between EUREF-FIN ellipsoidal heights and N60 or N2000 are performed using geoid models FIN2000 and FIN2005N00, respectively.

## Using the coordinate transformation Service

### Selecting geodetic coordinate reference systems

First, select the input and output coordinate reference systems. You can select the systems directly using the drop-down menus for each geodetic coordinate reference system. If heights are transformed at the same time, the input data contains vertical coordinates and you also need to select the input and output vertical coordinate reference systems.

If you wish to limit the list of selectable geodetic coordinate reference systems, you can first select the datum in the drop-down menu 'Geodetic datum'. You can also limit the list by selecting the coordinate system in the menu 'Coordinate system'. If you select 'Cartesian 2D', a new menu, 'System of map projections', will appear. In all drop-down menus, you can cancel a selection by clicking the 'x' to the right of the selected value.

You can also select the geodetic coordinate reference systems using the EPSG code by selecting 'Filter coordinate reference systems: With EPSG code' at the top of the window. When you select the input and output coordinate reference systems, the coordinate tables and their headers at the bottom of the page are updated to match the selected system.

### Selecting the coordinate information source

You can set input coordinates in three ways; by using the keyboard and typing the coordinates in the input coordinate table, by importing from a file or by selecting locations on the map. Under the heading 'Coordinate information source', you can select how input coordinates are set. If you selected 'Using keyboard', you can type the coordinates directly into the table. The table can hold a maximum of 100 coordinate points.

Another alternative is to import the input coordinates from a file. The maximum file size is 50 MB. When you select this alternative, a new window will appear where you can select options for the input file. You can select a file by dragging it onto the rectangular area at the top of the 'Input properties' window or from the file list ('select by browsing'). The name of the selected file will appear inside the rectangle. In the selection window you can also select the following options:

- Number of header rows: the number of header rows above the coordinate rows in the file
- Angle pattern: this selection only appears if the coordinates in the reference system are shown as angle values
- Decimal separator: the decimal separator used in coordinate values
- Coordinate separator: the separator used between coordinate values in the file
- Coordinates contain identifiers: by selecting this option, you announce that there is a coordinate identifier at the start of each row in the file
- Coordinates reversed: by selecting this option, you announce that the coordinates in the file are in reverse order in comparison with the system definition

The first 100 rows in the file are shown in the input coordinates table. If there are more rows in the file, they will be uploaded to the service, but not shown in the table. The purpose of the table is to act as a preview to ensure that coordinates have been read correctly from the file.

The third option for setting input coordinates is to select the coordinate points on the map. If you select this option, the input coordinate system must always be ETRS-TM35FIN, because Paikkatietoikkuna's map uses this system. If another input coordinate system has been selected, the user is shown a warning and ETRS-TM35FIN will be selected automatically as the input system.

### Transforming coordinates

When you have selected the input and output coordinate systems and set the coordinates to be transformed, you can start the coordinate transformation function. There are two ways of doing this. When you click the 'Transform' button, the input coordinates will be read from the table on the left and the output coordinates shown in the table on the right. If the input file contains more than 100 coordinates to be transformed, the table will function as a preview so that you can ensure that the output coordinates look sensible.

It is also possible to export the output coordinates into a file using the 'Transform into file' button. This is essential, if there are more than 100 coordinate points to be transformed. The transformation of a large number of points can last several minutes. When you transform into a file, a new window opens where you can give additional instructions for the export into file as follows:

- File name
- Decimal precision: the decimal precision for output coordinates can be selected as a numeric value in the interval 1 m–0.1 mm.
- Decimal separator: decimal separator used in coordinate values
- Coordinate separator: separator character used between coordinate values in the output file
- Line separator: end-of-line character used in one of the operating systems Windows/DOS, Unix or MacOS
- Add identifiers: identifiers are created for coordinate points in a numerical sequence (if the input file contains point identifiers and these were included when the file was read into the system, these identfiers are used)
- Coordinates reversed: coordinates are written into the file in reverse order as compared to the system definition
- Write header row into file: the coordinate system will be shown in the header row and if the input file contains header rows, these are included in the output
- Include end-of-row markers in output: any extra characters in the input file following the coordinates in each row are included in the output file
- Use cardinals (N, E, W, S): cardinals are shown with latitudes and longitudes, that is whether the latitude is North or South and the longitude East or West.

### Other functions

Use the function 'Empty tables' to empty both the input and output coordinates tables.

Use the function 'Show locations on the map' to show the locations of points to be transformed on the map. The input coordinates of each point will be shown next to the point they refer to.