Couche \u2192 G\u00e9or\u00e9f\u00e9rencer\n<\/code><\/pre>\n\n\n<\/div><\/div>\n\n\n\n
\n\n\n\n<\/a><\/figure>\n\n\n\n
\n\n\n\n<\/span>3. Charger l\u2019image \u00e0 g\u00e9or\u00e9f\u00e9rencer<\/span><\/h2>\n\n\n\nDans la fen\u00eatre du g\u00e9or\u00e9f\u00e9renceur :<\/p>\n\n\n<\/div><\/div><\/div><\/div><\/p>\n\n\n\nFichier \u2192 Ouvrir raster\n<\/code><\/pre>\n\n\n<\/div><\/div>\n\n\n\n
S\u00e9lectionnez votre image (JPEG, PNG, TIFF\u2026).<\/p>\n\n\n\n
\n\n\n\n<\/a><\/figure>\n\n\n\n
\n\n\n\n<\/span>4. Ajouter des points de contr\u00f4le<\/span><\/h2>\n\n\n\nC\u2019est l\u2019\u00e9tape la plus importante.<\/p>\n\n\n\n
Cliquez sur :<\/p>\n\n\n<\/div><\/div><\/div><\/div><\/p>\n\n\n\nAjouter un point\n<\/code><\/pre>\n\n\n<\/div><\/div>\n\n\n\n
Puis :<\/p>\n\n\n\n
\ncliquez sur un point identifiable de l\u2019image<\/li>\n\n\n\n
indiquez ses coordonn\u00e9es<\/li>\n<\/ol>\n\n\n\nDeux m\u00e9thodes :<\/p>\n\n\n\n
<\/span>✔ saisir les coordonn\u00e9es manuellement<\/span><\/h3>\n\n\n\n<\/span>✔ cliquer sur la carte (m\u00e9thode recommand\u00e9e)<\/span><\/h3>\n\n\n\n\nUtilisez une couche de r\u00e9f\u00e9rence (OpenStreetMap par exemple, ou comme dans l’exemple une couche d\u00e9j\u00e0 g\u00e9or\u00e9f\u00e9renc\u00e9e).<\/p>\n<\/blockquote>\n\n\n\n
\n\n\n\n<\/span>5. Choisir la transformation<\/span><\/h2>\n\n\n\nCliquez sur :<\/p>\n\n\n
<\/div><\/div><\/div><\/div><\/p>\n\n\n\nParam\u00e8tres de transformation\n<\/code><\/pre>\n\n\n<\/div><\/div>\n\n\n\n
Param\u00e8tres recommand\u00e9s :<\/p>\n\n\n\n
\nType : Polynomial 1 (Affine)<\/strong><\/li>\n\n\n\n
M\u00e9thode de r\u00e9\u00e9chantillonnage : Nearest neighbor<\/strong><\/li>\n\n\n\n
Syst\u00e8me de coordonn\u00e9es : EPSG:4326<\/a> ou EPSG:3857<\/strong><\/li>\n<\/ul>\n\n\n\n
\n\n\n\n<\/span>6. Lancer le g\u00e9or\u00e9f\u00e9rencement<\/span><\/h2>\n\n\n\nCliquez sur :<\/p>\n\n\n
<\/div><\/div><\/div><\/div><\/p>\n\n\n\nD\u00e9marrer le g\u00e9or\u00e9f\u00e9rencement\n<\/code><\/pre>\n\n\n<\/div><\/div>\n\n\n\n
QGIS cr\u00e9e un nouveau raster g\u00e9or\u00e9f\u00e9renc\u00e9.<\/p>\n\n\n\n
\n\n\n\n<\/span>7. V\u00e9rifier le r\u00e9sultat<\/span><\/h2>\n\n\n\nAjoutez le raster dans QGIS.<\/p>\n\n\n\n
V\u00e9rifiez que :<\/p>\n\n\n\n
\nl\u2019image est bien align\u00e9e<\/li>\n\n\n\n
les objets correspondent aux donn\u00e9es existantes<\/li>\n<\/ul>\n\n\n\n
\n\n\n\n<\/span>8. Conseils pour un bon g\u00e9or\u00e9f\u00e9rencement<\/span><\/h2>\n\n\n\n✔ Utiliser au moins 4 points<\/strong>
✔ R\u00e9partir les points sur toute l\u2019image
✔ Choisir des points pr\u00e9cis (croisements, angles\u2026)
✔ \u00c9viter les zones floues<\/p>\n\n\n\n
\n\n\n\n<\/span>9. Probl\u00e8mes fr\u00e9quents<\/span><\/h2>\n\n\n\n<\/span>L\u2019image est d\u00e9cal\u00e9e<\/span><\/h3>\n\n\n\nCause :<\/p>\n\n\n\n
\npoints mal plac\u00e9s<\/li>\n\n\n\n
mauvais CRS<\/li>\n<\/ul>\n\n\n\n
\n\n\n\n<\/span>L\u2019image est d\u00e9form\u00e9e<\/span><\/h3>\n\n\n\nCause :<\/p>\n\n\n\n
\ntransformation inadapt\u00e9e<\/li>\n\n\n\n
points mal r\u00e9partis<\/li>\n<\/ul>\n\n\n\n
\n\n\n\n<\/span>Mauvais positionnement global<\/span><\/h3>\n\n\n\nV\u00e9rifiez :<\/p>\n\n\n\n
\nle syst\u00e8me de coordonn\u00e9es<\/li>\n\n\n\n
la pr\u00e9cision des points<\/li>\n<\/ul>\n\n\n\n
\n\n\n\n<\/span>10. FAQ<\/span><\/h2>\n\n\n\n<\/span>Combien de points faut-il ?<\/span><\/h3>\n\n\n\nMinimum 3<\/strong>, mais 4 \u00e0 10 points<\/strong> donnent de meilleurs r\u00e9sultats.<\/p>\n\n\n\n
\n\n\n\n<\/span>Quel type de transformation choisir ?<\/span><\/h3>\n\n\n\n\nAffine (Polynomial 1) \u2192 le plus courant<\/li>\n\n\n\n
Polynomial 2 ou 3 \u2192 pour des d\u00e9formations plus complexes<\/li>\n<\/ul>\n\n\n\n
\n\n\n\n<\/span>Peut-on g\u00e9or\u00e9f\u00e9rencer un PDF ?<\/span><\/h3>\n\n\n\nOui, en l\u2019ouvrant comme raster dans QGIS.<\/p>\n\n\n\n
\n\n\n\n<\/span>Conclusion<\/span><\/h2>\n\n\n\nLe g\u00e9or\u00e9f\u00e9rencement est une \u00e9tape essentielle pour int\u00e9grer des images dans un projet SIG.<\/p>\n\n\n\n
En ajoutant des points de contr\u00f4le pr\u00e9cis et en choisissant les bons param\u00e8tres, il devient tr\u00e8s simple d\u2019aligner une image avec des donn\u00e9es g\u00e9ographiques dans QGIS.<\/p>\n\n\n\n
\n\n\n\n<\/p>\n","protected":false},"excerpt":{"rendered":"
Le g\u00e9or\u00e9f\u00e9rencement dans QGIS permet d\u2019aligner une image avec des coordonn\u00e9es r\u00e9elles \u00e0 l\u2019aide de points de contr\u00f4le. En pratique, il suffit d\u2019ajouter des points de contr\u00f4le pour associer des pixels \u00e0 des coordonn\u00e9es g\u00e9ographiques. Dans…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"give_campaign_id":0,"_bbp_topic_count":0,"_bbp_reply_count":0,"_bbp_total_topic_count":0,"_bbp_total_reply_count":0,"_bbp_voice_count":0,"_bbp_anonymous_reply_count":0,"_bbp_topic_count_hidden":0,"_bbp_reply_count_hidden":0,"_bbp_forum_subforum_count":0,"sfsi_plus_gutenberg_text_before_share":"","sfsi_plus_gutenberg_show_text_before_share":"","sfsi_plus_gutenberg_icon_type":"","sfsi_plus_gutenberg_icon_alignemt":"","sfsi_plus_gutenburg_max_per_row":"","_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[62,4568],"tags":[1903,4618,58,17,1901],"class_list":["post-16660","post","type-post","status-publish","format-standard","hentry","category-qgis-2","category-tutoriel-fr","tag-cartographie","tag-georeferencement","tag-qgis","tag-raster","tag-sig"],"aioseo_notices":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p6XU0A-4kI","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/posts\/16660","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/comments?post=16660"}],"version-history":[{"count":0,"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/posts\/16660\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/media?parent=16660"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/categories?post=16660"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/tags?post=16660"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
<\/span>2. Ouvrir le g\u00e9or\u00e9f\u00e9renceur dans QGIS<\/span><\/h2>\n\n\n\nDans QGIS :<\/p>\n\n\n<\/div>

<\/span>3. Charger l\u2019image \u00e0 g\u00e9or\u00e9f\u00e9rencer<\/span><\/h2>\n\n\n\nDans la fen\u00eatre du g\u00e9or\u00e9f\u00e9renceur :<\/p>\n\n\n<\/div>

<\/span>4. Ajouter des points de contr\u00f4le<\/span><\/h2>\n\n\n\nC\u2019est l\u2019\u00e9tape la plus importante.<\/p>\n\n\n\nCliquez sur :<\/p>\n\n\n<\/div>
