On Mon, Sep 15, 2025 at 04:01:21PM +0300, Mykyta Kozlov wrote:
> Following example converts cartesian coordinates in the LKS94 coordinate
> system, which has EPSG (SRID) code 3346 to lat-long over WG84, which has
> 4326 EPSG code,
> with precision up to 8 decimal digits (~1.1 mm accurate).
>
> cs2cs +init=epsg:3346 +to +init=epsg:4326 -f "%.8f" coords_file_lks94
> > coords_file_wgs84
Whether it's actually *accurate* to about 1mm depends on whether the
coordinate reprojection can be done that accurately.
You can check this with projinfo:
$ projinfo --summary -s EPSG:3346 -t EPSG:4326
Candidate operations found: 1
unknown id, Inverse of Lithuania 1994 + LKS94 to WGS 84 (1), 1 m, Lithuania
- onshore and offshore.
The "1 m" part is telling you this transformation is only accurate to
1 *metre* (which is not a problem for many uses e.g. plotting on a
map or if you want to find an entrance using GPS).
If you run without `--summary` you can see why this is the case here (amongst
much other output):
REMARK["LKS94 is a national realization of ETRS89 and coincident to WGS 84
within 1 metre. This transformation has an accuracy equal to the coincidence
figure."]]],
Some transformations are more accurate:
$ projinfo --summary -s EPSG:3857 -t EPSG:4326
Candidate operations found: 1
INVERSE(EPSG):3856, Inverse of Popular Visualisation Pseudo-Mercator, 0 m,
World.
Some less:
$ projinfo --summary -s EPSG:26922 -t EPSG:4326
Candidate operations found: 1
unknown id, Inverse of UTM zone 22N + NAD83 to WGS 84 (1), 4 m, North
America - onshore and offshore: Canada - Alberta; British Columbia; Manitoba;
New Brunswick; Newfoundland and Labrador; Northwest Territories; Nova Scotia;
Nunavut; Ontario; Prince Edward Island; Quebec; Saskatchewan; Yukon. United
States (USA) - Alabama; Alaska (mainland); Arizona; Arkansas; California;
Colorado; Connecticut; Delaware; Florida; Georgia; Idaho; Illinois; Indiana;
Iowa; Kansas; Kentucky; Louisiana; Maine; Maryland; Massachusetts; Michigan;
Minnesota; Mississippi; Missouri; Montana; Nebraska; Nevada; New Hampshire; New
Jersey; New Mexico; New York; North Carolina; North Dakota; Ohio; Oklahoma;
Oregon; Pennsylvania; Rhode Island; South Carolina; South Dakota; Tennessee;
Texas; Utah; Vermont; Virginia; Washington; West Virginia; Wisconsin; Wyoming.
And some unknown:
$ projinfo --summary -s EPSG:9712 -t EPSG:4326
Candidate operations found: 1
unknown id, Inverse of UTM zone 24N + Ballpark geographic offset from NAD83
to WGS 84, unknown accuracy, World, has ballpark transformation
Cheers,
Olly
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