S-JTSK (Ferro) / Krovak to KML & KMZ

Good to know

• Coordinates in this system count positive to the west and south. Enter the westing (Y) in the easting field and the southing (X) in the northing field.
• Datum: Treated as WGS 84, no shift (the datums agree to about a metre or better).

Convert a whole spreadsheet

For now, convert points in this system one at a time with the converter above. Whole-sheet conversion for grids that count to the west and south is being added to the web and Windows apps.

Common mistakes with S-JTSK (Ferro) / Krovak

• Feet entered as metres. S-JTSK (Ferro) / Krovak is in metres. Coordinates copied from a drawing in feet must be converted first, or every point moves outwards from the grid's origin.
• Forgetting the datum. S-JTSK (Ferro) / Krovak is not on WGS 84: treated as WGS 84, no shift (the datums agree to about a metre or better). Picking a WGS 84 grid with the same projection instead leaves the points off by that amount.
• Signs of the coordinates. S-JTSK (Ferro) / Krovak counts its axes west and south. Keep the signs exactly as the survey gives them; flipping them moves points across the origin.
• Points outside the grid's area. S-JTSK (Ferro) / Krovak is meant for Czechia; Slovakia. Points well outside that area convert with growing error; the converter flags them so you can choose the right grid.
• A local site grid. If every point is off by the same distance and direction, the drawing may be on a local site grid. Calibrate on three or more known control points instead.

New to this? Read how to convert easting and northing to latitude and longitude.