{"id":8585,"date":"2019-04-26T00:36:09","date_gmt":"2019-04-25T22:36:09","guid":{"rendered":"http:\/\/www.sigterritoires.fr\/?p=8585"},"modified":"2019-04-26T17:48:51","modified_gmt":"2019-04-26T15:48:51","slug":"arcgis-multiple-attribute-1-n-spatial-join","status":"publish","type":"post","link":"https:\/\/www.sigterritoires.fr\/index.php\/en\/arcgis-multiple-attribute-1-n-spatial-join\/","title":{"rendered":"ArcGis: Multiple attribute (1-n) spatial join"},"content":{"rendered":"\n

Joins between tables or layers pose virtually no problem when we have a\nunique match between the two elements we are trying to join. For one record of\nthe reference table or layer, there is one or no record in the table or layer\nto be joined. The resulting table or layer of the join can be treated as any\nother table or layer. <\/p>\n\n\n\n

Things always get complicated when the table or layer to be joined\ncontains more than one record corresponding to the same reference record. This\nis called a 1-n relationship. We will discuss a hidden option that allows us to\nanswer some of the questions we have in the event of 1-n type space joins.\nFirstly, let’s use a simple example. <\/p>\n\n\n\n\n\n\n\n

We have a layer of protected areas, for example the ZNIEFFs (natural\nareas of fauna, flora or  ecological\ninterest). <\/p>\n\n\n\n

You want to know which municipalities are affected by each zone present\nin the ZNIEFF layer. <\/p>\n\n\n\n

The simplest would be to add an attribute to the ZNIEFF table containing\nthe list of the communes affected by each zone \n\nTherefore, we obtain the ZNIEFF layer and a Municipalities\nlayer   \n\n\n\n<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The available join in the layer contextual menu in ArcMap only allows\nthe calculation of the number of municipalities that intersect the zone. \n\nWe have at our disposal the Spatial Join<\/em><\/strong>\ntool in the Analysis -> Overlay<\/em><\/strong> toolbox   \n\n\n\n<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nThis\ntool has an option   which allows for single or multiple joins. But if we\nrun the tool with the multiple option   :   \n\n\n\n<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nthe\nresult obtained is the following:   \n\n\n\n<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The area with the id 142 (Target_id) is over the municipalities of\nSaint-Eloy   and Tr\u00e9hou. The tool produces two identical polygons, one\nwith the attributes of Saint-Eloy and the other with the attributes of the\n  Tr\u00e9hou. <\/p>\n\n\n\n

But that’s not what we want. In order to know which are the affected\nmunicipalities by this area, we have to make a request. What we want is an\nattribute that contains the list of municipalities. <\/p>\n\n\n\n

It is there where the hidden option will allow us to solve our problem. <\/p>\n\n\n\n

We will use the spatial join tool, but contrary to what we could think,\nwe will leave the option one to one<\/em> because it is actually what we want:\nan input zone must produce an output zone, and not several as previously\nhappened. <\/p>\n\n\n\n

On the other hand, it is at the output field level that we are going to\nchange something. <\/p>\n\n\n\n

In the attributes of the common layer we have a field that contains the\nname of the town: NOM_COM<\/em><\/strong> . If you right-click this field in the\nlist of output fields, you get a context menu with an option: Properties<\/em><\/strong>\n. This is the field we want to use to create a list of municipalities. <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\nThen,\nyou will get the properties window.\n\n\n\n<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n
  • Be sure to give enough space to\ncontain the resulting list. <\/li>
  • In the Merge Rule<\/em><\/strong> field , select Join<\/em><\/strong> . <\/li>
  • As Separator<\/em> , select the comma<\/em> . <\/li><\/ul>\n\n\n\n

    \n\n\n\n\n\nRun the tool, and the result is as follows:   \n\n\n\n<\/p>\n\n\n\n

    \"\"<\/figure>\n\n\n\n

    Right now, the tool has created a single polygon per input field, and\nthe COM_NAME field contains the list of affected municipalities separated  by commas. <\/p>\n\n\n\n

    Only problem with this trick: the Joining<\/em><\/strong> merge option is\nonly available for Text<\/em><\/strong> fields. So depending on the format of\nyour output table you will be limited in the field length: <\/p>\n\n\n\n

    • if you work with shapefiles, the\nresult is limited to 254   characters. <\/li><\/ul>\n\n\n\n

      \n\nif you are working with a personal geodatabase,\nforget to work with the current version of ArcGis (10.3), it crashes! The tool tries to create a shape in an Access\n\n\n\n<\/p>\n\n\n\n

      \"\"<\/figure>\n\n\n\n
      • database … <\/li>
      • if you are working with a\ngeodatabase file, the length limit is   2 147 483 647 characters …\nalways enough! On the other hand, it is you who\nset the size of the field before executing the tool. If you do not give enough space for the output list\nyou will get an error message and the tool will stop running. <\/li><\/ul>\n","protected":false},"excerpt":{"rendered":"

        Joins between tables or layers pose virtually no problem when we have a unique match between the two elements we are trying to join. For one record of the reference table or layer, there is one…<\/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":[1260],"tags":[],"class_list":["post-8585","post","type-post","status-publish","format-standard","hentry","category-non-classe-en"],"aioseo_notices":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p6XU0A-2et","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/posts\/8585","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=8585"}],"version-history":[{"count":0,"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/posts\/8585\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/media?parent=8585"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/categories?post=8585"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.sigterritoires.fr\/index.php\/wp-json\/wp\/v2\/tags?post=8585"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}