Just a follow up,
I've added a sql file to the sql files that build the proj.db sqlite database
with these 2 lines:
-- NTFP+NGF-IGN69 height
INSERT INTO compound_crs VALUES('RDI','NTFP.IGN69','NTF geographiques Paris
(gr) + NGF-IGN69 height','','IGNF','NTFP','EPSG','5720',0);
INSERT INTO usage
VALUES('RDI','USAGE_COMPOUND_CRS_NTFP.IGN69','compound_crs','RDI','NTFP.IGN69','PROJ','EXTENT_UNKNOWN','PROJ','SCOPE_UNKNOWN');
and recompiled the library. It works perfectly.
echo 0 56.000000 0 | ./cs2cs -f "%.3f" --3d +from IGNF:NTFP +to IGNF:ETRS89LCC
--> 3474788.212 2655358.229 42.989
echo 0 56.000000 0 | ./cs2cs -f "%.3f" --3d +from RDI:NTFP.IGN69 +to
IGNF:ETRS89LC --> 3474789.997 2655359.291 43.644
I will see if someone in the Institute could clarify these codes and update
them in a future release of PROJ.
Thanks for your help,
N.
De: "Even Rouault" <[email protected]>
À: "Nicolas Bellaiche" <[email protected]>
Cc: "proj" <[email protected]>
Envoyé: Mardi 20 Février 2024 19:05:55
Objet: Re: [PROJ] Help needed for a cs2cs pipeline with shift grids
Le 20/02/2024 à 18:53, Nicolas Bellaiche a écrit :
Hi Even
Thanks for your kind and developed answer.
I've tried with the EPSG equivalents: ( [
https://www.sandre.eaufrance.fr/jeu-de-donnees/projection-des-coordonn%C3%A9es?lang=fr
|
https://www.sandre.eaufrance.fr/jeu-de-donnees/projection-des-coordonnées?lang=fr
] )
echo 0 56.000000 0 | ./cs2cs +from EPSG:4807 +to EPSG:3034
But the result doesn't make any sense:
-1640975.39 10099142.17 0.00
Is there something with the units that is not correct maybe?
No, just the usual axis order issue as EPSG geographic CRS are lat, long
ordered, whereas IGNF uses the opposition order. So:
$ echo 56 0 | cs2cs EPSG:4807 EPSG:3034
2655358.23 3474788.21 0.00
BQ_BEGIN
This works well:
echo 0 56.000000 0 | PROJ_NETWORK=ON ./cs2cs -d 3 "NTF geographiques Paris (gr)
+ NGF-IGN69 height" IGNF:ETRS89LCC --3d
and I have a few questions about it:
1) the result remains unchanged if I remove or put PROJ_NETWORK to OFF. What
does it do exactly?
BQ_END
If you have already all the grids in the PROJ_DATA directory, PROJ_NETWORK will
not do anything. This is just for people who don't have grids installed locally
BQ_BEGIN
2) Does the string " NTF geographiques Paris (gr) + NGF-IGN69 height"
correspond to an entry in the CRS database proj.db or is it interpreted as a
compounded system because PROJ parses the string?
BQ_END
Yes, there's logic in PROJ to split "A + B" into A and B, do simple CRS lookups
for A and B in the database, and create a compound CRS from that.
BQ_BEGIN
There is no simple code like EPSG or IGNF related to it? Can we create one
easily?
BQ_END
yes, cf [
https://github.com/OSGeo/PROJ/blob/master/data/sql/transformations_czechia_extra.sql#L86
|
https://github.com/OSGeo/PROJ/blob/master/data/sql/transformations_czechia_extra.sql#L86
] for a custom CompoundCRS
You can also get the potential SQL statements (that can be simplified and
improved) with:
$ bin/projinfo IGNF:NTFP+EPSG:5720 -o SQL --output-id SOME_AUTH:MY_COMPOUND_CRS
-q
INSERT INTO geodetic_crs VALUES('SOME_AUTH','COMPONENT_MY_COMPOUND_CRS_1','NTF
geographiques Paris (gr)','','geographic
2D','EPSG','6425','EPSG','6807',NULL,0);
INSERT INTO scope
VALUES('SOME_AUTH','SCOPE_geodetic_crs_COMPONENT_MY_COMPOUND_CRS_1','NATIONALE,
HISTORIQUE',0);
INSERT INTO extent
VALUES('SOME_AUTH','EXTENT_geodetic_crs_COMPONENT_MY_COMPOUND_CRS_1','FRANCE
METROPOLITAINE (CORSE COMPRISE)','FRANCE METROPOLITAINE (CORSE
COMPRISE)',41,52,-5.5,10,0);
INSERT INTO usage
VALUES('SOME_AUTH','USAGE_GEODETIC_CRS_COMPONENT_MY_COMPOUND_CRS_1','geodetic_crs','SOME_AUTH','COMPONENT_MY_COMPOUND_CRS_1','SOME_AUTH','EXTENT_geodetic_crs_COMPONENT_MY_COMPOUND_CRS_1','SOME_AUTH','SCOPE_geodetic_crs_COMPONENT_MY_COMPOUND_CRS_1');
INSERT INTO compound_crs VALUES('SOME_AUTH','MY_COMPOUND_CRS','NTF
geographiques Paris (gr) + NGF-IGN69
height','','SOME_AUTH','COMPONENT_MY_COMPOUND_CRS_1','EPSG','5720',0);
INSERT INTO usage
VALUES('SOME_AUTH','USAGE_COMPOUND_CRS_MY_COMPOUND_CRS','compound_crs','SOME_AUTH','MY_COMPOUND_CRS','PROJ','EXTENT_UNKNOWN','PROJ','SCOPE_UNKNOWN');
This could be simplified by just taking the last 2 statements and modify
'SOME_AUTH','COMPONENT_MY_COMPOUND_CRS_1' to 'IGNF', 'NTFP' (I believe this SQL
synthesis code only references EPSG objects, hence the redefinition of an
equivalent of IGNF:NTFP)
BQ_BEGIN
3) Where can I see where this crs"NTF geographiques Paris (gr) + NGF-IGN69
height" is defined in the sql commands used to build it?
BQ_END
well, if you want all the lineage, this is a cascade of INSERT statement. You
have to fetch the geographic and vertical CRS, their datum, coordinate systems,
axis, units in the relevant tables.
BQ_BEGIN
Nicolas Bellaiche
De: "Even Rouault" [ mailto:[email protected] |
<[email protected]> ]
À: "Nicolas Bellaiche" [ mailto:[email protected] |
<[email protected]> ] , "proj" [ mailto:[email protected] |
<[email protected]> ]
Envoyé: Dimanche 18 Février 2024 15:16:44
Objet: Re: [PROJ] Help needed for a cs2cs pipeline with shift grids
Nicolas,
I believe the Helmert transformation is used when using IGNF codes, because the
IGNF database has only recorded the use of the ntf_r93 grid for NTF to RGF93,
but not for NTF to ETRS89 (by the way, just reiterating that IGN is more than
welcome to take over on maintenance & updates of the IGNF part of the PROJ
database). And when transforming between 2 IGNF codes, PROJ by default will
only consider transformations in the IGNF domain. But if you use EPSG codes,
then ntf_r93 is available to transforme between NTF and ETRS89.
To get a vertical transformation, you also need to use 3D CRS.
For example
projinfo -s "NTF geographiques Paris (gr) + NGF-IGN69 height" -t IGNF:ETRS89LCC
--3d --spatial-test intersects
reports the following pipeline:
unknown id, axis order change (2D) + NTF (Paris) to NTF (1) + NTF to RGF93 v1
(1) + Inverse of RGF93 v1 to NGF-IGN69 height (1) + RGF93 v1 to ETRS89 (1) +
axis order change (geographic3D horizontal) + ETRS89 LAMBERT CONFORMAL CONIC,
1.6 m, France - mainland onshore., at least one grid missing
PROJ string:
+proj=pipeline
+step +proj=unitconvert +xy_in=grad +xy_out=rad
+step +inv +proj=longlat +ellps=clrk80ign +pm=paris
+step +proj=push +v_3
+step +proj=cart +ellps=clrk80ign
+step +proj=xyzgridshift +grids=fr_ign_gr3df97a.tif +grid_ref=output_crs
+ellps=GRS80
+step +inv +proj=cart +ellps=GRS80
+step +proj=pop +v_3
+step +proj=vgridshift +grids=fr_ign_RAF18.tif +multiplier=1
+step +proj=lcc +lat_0=52 +lon_0=10 +lat_1=35 +lat_2=65 +x_0=4000000
+y_0=2800000 +ellps=GRS80
Here, as there's a mix of objects from different authorities (IGNF and EPSG),
then EPSG transformations are considered, hence you get the gr3df97a grid.
$ echo 0 56.000000 0 | PROJ_NETWORK=ON bin/cs2cs -d 3 "NTF geographiques Paris
(gr) + NGF-IGN69 height" IGNF:ETRS89LCC --3d
3474789.997 2655359.291 43.644
which is the application of the above pipeline:
$ echo 0 56.000000 0 | PROJ_NETWORK=ON bin/cct -d 3 +proj=pipeline +step
+proj=unitconvert +xy_in=grad +xy_out=rad +step +inv +proj=longlat
+ellps=clrk80ign +pm=paris +step +proj=push +v_3 +step +proj=cart
+ellps=clrk80ign +step +proj=xyzgridshift +grids=fr_ign_gr3df97a.tif
+grid_ref=output_crs +ellps=GRS80 +step +inv +proj=cart +ellps=GRS80 +step
+proj=pop +v_3 +step +proj=vgridshift +grids=fr_ign_RAF18.tif +multiplier=1
+step +proj=lcc +lat_0=52 +lon_0=10 +lat_1=35 +lat_2=65 +x_0=4000000
+y_0=2800000 +ellps=GRS80
If you want to get exactly the below pipeline, you'll have to tweak proj.db to
create a compound CRS for "NTF geographiques Paris (gr) + NGF-IGN69 height",
and then create a custom record in other_transformation for the transformation
between this compound CRS and (a 3D projected CRS derived from) IGNF:ETRS89LCC.
Cf data/sql/other_transformation_custom.sql for potential inspiration
Even
Le 15/02/2024 à 19:46, Nicolas Bellaiche via PROJ a écrit :
BQ_BEGIN
Hi there,
I try to make a conversion using shiftgrids from IGNF: NTFP to IGNF:ETRS89LCC.
By default, it seems that it uses the helmert approximation between the 2 crs
and i cannot figure out how to use the grid fr_ign_ntf_r93.
So far i've found how to create a pipeline that works with cct, but i'd like to
have a code that represents the crs and be able to go to different destination
crs with the cs2cs application. Any idea?
(helmert approx + no geoid with the standard codes)
echo 0 56 0 | ./cs2cs + from IGNF:NTFP +to IGNF:ETRS89LCC
result : 3474788.21 2655358.23 0.00
(correct pipeline)
echo 0 56.000000 0 | PROJ_DEBUG=3 ./cct +proj=pipeline +step +proj=unitconvert
+xy_in=grad +xy_out=rad +step +inv +proj=longlat +ellps=clrk80ign +pm=paris
+step +proj=hgridshift +grids=fr_ign_ntf_r93.tif +step +inv +proj=vgridshift
+grids=RAF09.gtx +step +proj=lcc +lat_0=52 +lon_0=10 +lat_1=35 +lat_2=65
+x_0=4000000 +y_0=2800000 +ellps=GRS80
result : 3474789.9972 2655359.2908 43.6421 inf
reference from THE official IGN/SGN dataset:
3474789.997 2655359.291 43.642
Thanks a lot for your help,
Nicolas Bellaiche
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BQ_END
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BQ_END
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free, but my time generally not.
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