PROJCRS["Monte Mario / Italy zone 1",
    BASEGEODCRS["Monte Mario",
        DATUM["Monte Mario",
            ELLIPSOID["International 1924",6378388,297,
                LENGTHUNIT["metre",1]]],
        PRIMEM["Greenwich",0,
            ANGLEUNIT["degree",0.0174532925199433]]],
    CONVERSION["Italy zone 1",
        METHOD["Transverse Mercator",
            ID["EPSG",9807]],
        PARAMETER["Latitude of natural origin",0,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8801]],
        PARAMETER["Longitude of natural origin",9,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8802]],
        PARAMETER["Scale factor at natural origin",0.9996,
            SCALEUNIT["unity",1],
            ID["EPSG",8805]],
        PARAMETER["False easting",1500000,
            LENGTHUNIT["metre",1],
            ID["EPSG",8806]],
        PARAMETER["False northing",0,
            LENGTHUNIT["metre",1],
            ID["EPSG",8807]]],
    CS[Cartesian,2],
        AXIS["easting (X)",east,
            ORDER[1],
            LENGTHUNIT["metre",1]],
        AXIS["northing (Y)",north,
            ORDER[2],<br>
            LENGTHUNIT["metre",1]],
    AREA["Italy - west of 12°E"],
    BBOX[36.53,5.94,47.04,12],
    ID["EPSG",3003]]

GEODCRS["WGS 84",
    DATUM["World Geodetic System 1984",
        ELLIPSOID["WGS 84",6378137,298.257223563,
            LENGTHUNIT["metre",1]]],
    PRIMEM["Greenwich",0,
        ANGLEUNIT["degree",0.0174532925199433]],
    CS[ellipsoidal,2],
        AXIS["geodetic latitude (Lat)",north,
            ORDER[1],
            ANGLEUNIT["degree",0.0174532925199433]],
        AXIS["geodetic longitude (Lon)",east,
            ORDER[2],
            ANGLEUNIT["degree",0.0174532925199433]],
    AREA["World"],
    BBOX[-90,-180,90,180],
    ID["EPSG",4326]]

PROJCRS["WGS 84 / UTM zone 32N",
    BASEGEODCRS["WGS 84",
        DATUM["World Geodetic System 1984",
            ELLIPSOID["WGS 84",6378137,298.257223563,
                LENGTHUNIT["metre",1]]],
        PRIMEM["Greenwich",0,
            ANGLEUNIT["degree",0.0174532925199433]]],
    CONVERSION["UTM zone 32N",
        METHOD["Transverse Mercator",
            ID["EPSG",9807]],
        PARAMETER["Latitude of natural origin",0,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8801]],
        PARAMETER["Longitude of natural origin",9,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8802]],
        PARAMETER["Scale factor at natural origin",0.9996,
            SCALEUNIT["unity",1],
            ID["EPSG",8805]],
        PARAMETER["False easting",500000,
            LENGTHUNIT["metre",1],
            ID["EPSG",8806]],
        PARAMETER["False northing",0,
            LENGTHUNIT["metre",1],
            ID["EPSG",8807]]],
    CS[Cartesian,2],
        AXIS["(E)",east,
            ORDER[1],
            LENGTHUNIT["metre",1]],
        AXIS["(N)",north,
            ORDER[2],
            LENGTHUNIT["metre",1]],
    AREA["World - N hemisphere - 6°E to 12°E - by country"],
    BBOX[0,6,84,12],
    ID["EPSG",32632]]

1. ESRI WKT: a dialect widely adopted by ESRI proprietary software.
2. GDAL WKT1: a dialect historically supported by the open source GDAL library.
3. WKT2:2015: as defined by ISO 19162:2015 standard specification (now superseded).
4. WKT2:2018: as defined by the more recent ISO 19162:2018 standard specification .

• The two main areas correspond to EPSG:3003 Monte Mario / Italy zone 1 and EPSG:3004 Monte Mario / Italy zone 2.
• The smallest areas correspond to the more specific areas of use now supported by PROJ.6

Concepts to keep well in mind

• forget the old proj-strings; they are no longer the best way for taking full profit from PROJ.6
• the best way to make the most of PROJ.6 capabilities is by leaving the library fully free to choose the best possible transformation from the origin and the destination CRSes.
  but this strictly requires that the library will be backed up by its own private database.

Additional concept

• srid, auth_name, auth_srid and ref_sys_name columns are still required in order to define all supported CRSes and to support relations based on Primary and Foreign Keys.
• but columns proj4text and srtext are now practically useless, because PROJ.6 is now capable to fully define any CRS by directly querying its own private database.
• Future Forecasts: both proj4text and srtext will be probably removed in some future version of SpatiaLite.
  For now they continue to be supported mainly to the benefit of previous versions of SpatiaLite being based on the now superseded PROJ.4

projinfo -s EPSG:4326 -t EPSG:32632 -o proj

• the optional argument area may be NULL (default setting).
  Otherwise it's expected to contain a valid Geometry in SRID=4326 (long/lat). When an area of use is explicitly supplied, then PROJ.6 may eventually use the corresponding BBOX for finely tuning the more accurate transformation.
• both the optional arguments proj_string_from and proj_string_to may be NULL (default setting).
  Otherwise they are expected to contain a valid string to be used for identifying the corresponding CRS.
  PROJ.6 accepts the following CRS strings:
  • traditional proj-strings used by all previous versions of PROJ, as e.g.
    • +proj=merc +a=6378137 +b=6378137 +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +k=1 +units=m +nadgrids=@null +wktext +no_defs
    • +proj=utm +zone=32 +south +ellps=WGS72 +towgs84=0,0,4.5,0,0,0.554,0.2263 +units=m +no_defs
    • +proj=utm +zone=32 +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m +no_defs
• any WKT expression defining a CRS.
• a CRS name as e.g.
  • WGS 84
  • WGS 84 / UTM zone 32N
  • IGM95 / UTM zone 33N
• any canonical CRS reference as e.g.
  • EPSG:4326
  • urn:ogc:def:crs:EPSG::3003

• Special case: if proj_string_to is NULL whilst proj_string_from is explicitly set, then it will interpreted as an user defined transformation string (possibly, as a transformation pipeline) as e.g.
  • +proj=pipeline
    +step +proj=axisswap +order=2,1
    +step +proj=unitconvert +xy_in=deg +xy_out=rad
    +step +proj=push +v_3
    +step +proj=cart +ellps=WGS84
    +step +inv +proj=helmert +x=-104.1 +y=-49.1 +z=-9.9 +rx=0.971 +ry=-2.917 +rz=0.714 +s=-11.68 +convention=position_vector
    +step +inv +proj=cart +ellps=intl
    +step +proj=pop +v_3
    +step +proj=tmerc +lat_0=0 +lon_0=9 +k=0.9996 +x_0=1500000 +y_0=0 +ellps=intl

Notes

• SpatiaLite does not constraints you in any way and fully respects users freedom carefully avoiding auto-magical assumptions.
  • The new extended signatures supported by ST_Transform closely mimic the most recent PROJ.6 API, so you are free to define your coordinates transformations in several different ways.
  • The default behavior of SpatiaLite when using PROJ.6 is to completely ignore the CRS definitions stored within the internal table spatial_ref_sys
    Any required CRS definition will be always retrieved from PROJ.6 itself that will simply receive a request in the form from EPSG:32632 to EPSG:3003.
  • If you have any good reason suggesting to do such a thing, you are anyway free to use any kind of proj-strings, WKT definitions or CRS names supported by PROJ.6.
    But this is under your full responsibility, and you must be well self-conscious of what are you doing.
• SpatiaLite encourages and promotes the most creative uses of PROJ.6, this including using your own customized transformation pipelines.
  Correctly using custom transformations isn't necessarily simple and easy, but it's a big opportunity for all skilled and talented power users.

Tech Note: using projinfo for discovering pipelines and areas of use

projinfo -s EPSG:4326 -t EPSG:3003 -o proj --spatial-test intersect
Candidate operations found: 3
-------------------------------------
Operation n°1:

unknown id, Inverse of Monte Mario to WGS 84 (4) + Italy zone 1, 4 m, Italy - mainland

PROJ string:
+proj=pipeline 
+step +proj=axisswap +order=2,1 
+step +proj=unitconvert +xy_in=deg +xy_out=rad 
+step +proj=push +v_3 
+step +proj=cart +ellps=WGS84 
+step +inv +proj=helmert +x=-104.1 +y=-49.1 +z=-9.9 +rx=0.971 +ry=-2.917 +rz=0.714 +s=-11.68 +convention=position_vector 
+step +inv +proj=cart +ellps=intl 
+step +proj=pop +v_3 
+step +proj=tmerc +lat_0=0 +lon_0=9 +k=0.9996 +x_0=1500000 +y_0=0 +ellps=intl

-------------------------------------
Operation n°2:

unknown id, Inverse of Monte Mario to WGS 84 (2) + Italy zone 1, 4 m, Italy - Sardinia onshore

PROJ string:
+proj=pipeline 
+step +proj=axisswap +order=2,1 
+step +proj=unitconvert +xy_in=deg +xy_out=rad 
+step +proj=push +v_3 
+step +proj=cart +ellps=WGS84 
+step +inv +proj=helmert +x=-168.6 +y=-34 +z=38.6 +rx=-0.374 +ry=-0.679 +rz=-1.379 +s=-9.48 +convention=position_vector 
+step +inv +proj=cart +ellps=intl 
+step +proj=pop +v_3 
+step +proj=tmerc +lat_0=0 +lon_0=9 +k=0.9996 +x_0=1500000 +y_0=0 +ellps=intl

-------------------------------------
Operation n°3:

unknown id, Inverse of Monte Mario to WGS 84 (11) + Italy zone 1, 10 m, Italy - Sicily Strait west of 13°E

PROJ string:
+proj=pipeline 
+step +proj=axisswap +order=2,1 
+step +proj=unitconvert +xy_in=deg +xy_out=rad 
+step +proj=push +v_3 
+step +proj=cart +ellps=WGS84 
+step +proj=helmert +x=230.47 +y=56.08 +z=-22.43 
+step +inv +proj=cart +ellps=intl 
+step +proj=pop +v_3 
+step +proj=tmerc +lat_0=0 +lon_0=9 +k=0.9996 +x_0=1500000 +y_0=0 +ellps=intl

• The best mode for taking full profit from PROJ.6 is by ignoring all CRS definitions contained into spatial_ref_sys, thus leaving PROJ free to choose the best possible approach. (and this is the default setting).
  This way you'll be absolutely sure that the most recent and fully detailed definitions will be always retrieved from the PROJ.6 own private database.
  This will be ensured even when processing some legacy DB being created by earlier versions and thus potentially containing an outdated spatial_ref_sys table.
• SpatiaLite fully respects users freedom avoiding any imposed constraint.
  If you think that using other different CRS definitions is a good idea, you are free to use traditional proj-strings, WKT definitions, CRS names and whatever else that may be deemed appropriate.
• SpatiaLite encourages and promotes the most creative uses of PROJ.6: using your own custom transformation pipelines isn't necessarily simple and easy, but is a big opportunity for all skilled and talented power users.

• new_path: a relative or absolute pathname leading to a valid PROJ's SQLite database.

• auth_name and auth_srid identify the intended CRS.
  auth_name can be NULL, and in this case EPSG will be assumed.

• auth_name and auth_srid identify the intended CRS.
  auth_name can be NULL, and in this case EPSG will be assumed.
• the optional argument style determines which specific WKT format should be adopted, and must be one between GDAL, ESRI, ISO-2015 or ISO-2018 (this latter being the default setting).
• the optional argument indented if set to TRUE will nicely format a multiline WKT expression, otherwise a single monolithic line lacking any white-space or new-line will be printed (the default is TRUE).
• the optional argument indentation determines how many white-spaces are to be used for indenting (only meaningful if indented=TRUE; the default values is 4).

• wkt_expr: the WKT expression to be evaluated.

• filename: the absolute or relative path leading to some Shapefile.
  Note: exactly as required by ImportSHP() filename must omit any .shp, .shx, .dbf or .prj suffix.

• Short conclusion: installing the software alone is not enough.
  The PROJ.6 private database proj.db must be properly installed as well, in order to ensure that anything runs smoothly.

1. the first place where proj.db will be searched is the same folder form where the EXE binary was initially loaded.
   Example: assuming that you are currently executing C:\myprogs\spatialite\bin\spatialite.exe
   • then an attempt will be made to connect C:\myprogs\spatialite\bin\proj.db
2. a second attempt will be made on behalf of the Public folder.
   Example: an attempt will be made to connect C:\Users\Public\spatialite\proj\proj.db
3. a third (and last) attempt will be made on behalf of the User folder.
   Example: an attempt will be made to connect C:\Users\sandro\spatialite\proj\proj.db

An useful diagnostic check

SELECT PROJ_GetDatabasePath();

• if NULL is returned, then PROJ.6 is definitely unable to connect to its own private SQLite database proj.db
  You have to carefully verify that it's really installed on one of the expected standard locations.
• otherwise the path leading to the currently connected proj.db will be returned.

• export "PROJ_LIB=/home/sandro/proj"
  echo $PROJ_LIB
  spatialite

• SET PROJ_LIB=C:\Users\sandro\proj
  echo %PROJ_LIB%
  spatialite_gui