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Axione-IPE-Viewer/notes.org

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* Notes
Vous pouvez trouver ici les notes plus ou moins en vrac que j'ai
prise lors de l'étude de ce projet. C'était la première fois que je
touchais a un GIS. Si c'est également votre cas, il y a
potentiellement des réponses a vos futures questions ici.
** Load Spatialite
1. Have libspatialite in your LD_LIBRARY_PATH.
2. Run =select load_extension("mod_spatialite");= at SQLite startup.
** How to Create a point
Example in this tutorial: https://gist.github.com/sixman9/805823
** How to Test Points
Use the spatial index table.
/!\ DO NOT USE =CONTAINS= to filter out data. It's not as performant as the spatial index.
See https://www.gaia-gis.it/gaia-sins/spatialite-cookbook/html/rtree.html for what's happening under the hood.
** Spatialite Getting Started
Petit test pour voir comment ça marche.
#+BEGIN_SRC
spatialite> CREATE TABLE points (id INTEGER PRIMARY KEY NOT NULL);
spatialite> SELECT AddGeometryColumn('points','dummypoints',3857,'POINT');
1
spatialite> INSERT INTO points (dummypoints) VALUES(Transform(MakePoint(384998.246399999,6366249.435399996366249.43539999,4964),3857));
spatialite> select * from points;
1|
spatialite> select AsText(dummypoints) from points;
#+END_SRC
** SRID, quezako?
- Bonne référence: https://www.gaia-gis.it/gaia-sins/spatialite-cookbook/html/srid.html
En pratique, on spécifie le SRID a spatialite en utiliant le code EPSG
- Projection règlementaire en France: RGF93, EPSG:2154
- Mercator (OSM/Google Maps): WGS84, EPSG:4326
D'après https://geodesie.ign.fr/index.php?page=rgf93, le RGF93 est compatible avec Mercator.
** DSPs to Ingest
ADTH AISN BEFO BTHD CTYF EURE FI44 NATH NIVE NPDC SART SHSN SIEL SPTH VAUC
** Requête sur l'Index Spatial
#+BEGIN_SRC sql
SELECT * FROM ipe
WHERE ROWID = (
SELECT ROWID FROM SpatialIndex
WHERE f_table_name = 'ipe'
AND search_frame = BuildMBR(
-1.405456066131592,
43.53722495535158,
-1.3643002510070803,
43.54475322429539,
4326)
);
#+END_SRC