Question 1

How to convert latitude/longitude to UTM using PROJ command line?

Accepted Answer

Use the cs2cs utility with CRS strings. For example, to convert WGS84 to UTM zone 33N: echo '12.34 56.78' | cs2cs +proj=latlong +datum=WGS84 +to +proj=utm +zone=33 +north. This outputs transformed coordinates directly.

Question 2

PROJ vs GDAL: which one is better for coordinate transformations?

Accepted Answer

GDAL often uses PROJ internally for transformations. Choose PROJ for fine-grained control over coordinate operations, but GDAL for higher-level raster/vector data processing that bundles transformations with other geospatial functions.

Question 3

Does PROJ support 3D coordinate transformations including height?

Accepted Answer

Yes, PROJ supports 3D transformations and vertical datums, but this requires specific data files (like geoid models) and proper configuration, which can add complexity to setups.

Question 4

How to install PROJ data files offline?

Accepted Answer

Download the proj-data package from the PROJ website, extract it to the PROJ_LIB directory, and disable network access in PROJ settings to rely solely on local files for transformations.

Question 5

What's the difference between the proj and cs2cs commands?

Accepted Answer

proj handles cartographic projections, while cs2cs transforms between any two coordinate reference systems, including datum shifts. cs2cs is more general and commonly used for CRS-to-CRS conversions.

Question 6

Can PROJ be used in Python for geospatial projects?

Accepted Answer

Yes, via bindings like pyproj, which wraps PROJ functionality for Python. However, it still requires PROJ and its data files installed, adding dependency management overhead.

PROJ

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