Reproject a Shapefile

Why reproject a shapefile

Data from a surveyor, a municipality or a colleague often comes in a coordinate system that does not match your project: a UTM zone when the web map needs WGS84, an old national grid when your other layers use ETRS89, or Web Mercator from an online export. Setting the project CRS in QGIS only changes how layers are drawn; to hand on a file in the right system, its coordinates must be transformed. This page does that with GDAL and PROJ, the libraries QGIS uses, in your browser: it reads the .prj, converts every vertex to the system you choose and writes a shapefile with a new .prj. If the shapefile has no .prj, you enter its system first. The map preview shows whether the data lands in the right place.

How to reproject a shapefile online

1. Drop the shapefile as a .zip, or select the .shp, .shx, .dbf and .prj files together.
2. Enter the target coordinate system as an EPSG code, or pick one from the list.
3. Click Reproject shapefile and download the zip with the new shapefile.

What to know about reprojecting

Reprojecting is not the same as assigning

Reprojecting changes every coordinate, for example from 556000, 6324000 in UTM zone 32N to 9.92, 57.06 in degrees, and writes a matching .prj. Assigning a system only replaces the .prj and leaves the numbers alone; that is only right when the .prj was missing or wrong. If your data lands in the wrong country or in the sea off Africa, the source system is usually wrong, not the target.

A missing .prj

Without a .prj, a shapefile does not say what system its numbers are in, and nothing can be transformed until you say it. The page asks for the source EPSG code when the .prj is missing; the size of the numbers is a hint: values between -180 and 180 are usually degrees, six- and seven-digit values are usually metres in UTM or a national grid.

Datum shifts and accuracy

Between systems on the same datum, such as UTM zones on ETRS89 or WGS84, the result is accurate to the millimetre. Changes of datum, such as OSGB36 for the British National Grid, NAD27, DHDN or other older national systems, are most exact with a grid file from the national mapping agency. Those grid files are not available in the browser, so PROJ uses the published average parameters, which can be off by one to a few metres. For survey-grade work, use QGIS or ogr2ogr with the grid installed.

Text, field names and file names

All attributes and field names are kept. Text is written as UTF-8 with a .cpg file, which QGIS and ArcGIS read correctly; an old program that ignores .cpg files may show letters such as ø or é wrongly. Date-time fields are kept as text, since a .dbf cannot store a time. Each shapefile keeps its name, and several shapefiles in one zip are reprojected together.

Lines are not bent

Only the vertices are transformed; a straight segment between two vertices stays straight. Over short distances that is invisible, but a long line with few vertices, such as a grid line or a country border drawn with two points, may be slightly off its true path in the new system.