For ST_3DDistance you have to have all dimensions in the same unit, or the answer will not make sense. So use ST_Transform to project your GPS points to a suitable meter based (if altitudes are in meters) projection for the area of the points.
In Moscow you can use UTM37, which is SRID 32637
So to transform your data use
Then you have to make the altitude the z-value of the geometries.
Since you have points it is easy. You can do something like:
-- If you have a table like this:
lat double precision,
lon double precision,
altitude double precision
-- First create a PostGIS geometry from lat, lon
--(I might be wrong about lat, lon, or lon, lat order, I never do this)
CREATE TABLE table_a AS
SELECT ST_SetSRID(ST_MakePoint(lat, lon), 4326) geom, altitude FROM the_table;
--Then transform (project) the data
CREATE TABLE table_b AS
SELECT ST_Transform(geom) geom, altitude FROM table_a;
-- And create a table with 3D points
CREATE TABLE points_3d
SELECT ST_MakePoint(ST_X(geom), ST_Y(geom), altitude) geom FROM table_b
Now you have PostGIS 3D geometries that you can use with ST_3DDistance.
You can of course put the queries above in one single query.