Creating relationship class in QGIS for uploading to ArcGIS Online?

Getting Relational: Linking Your QGIS Data in ArcGIS Online

So, you’re a QGIS whiz, comfortable wrangling geospatial data in the open-source world. But now you need to get that data, complete with its intricate relationships, up onto ArcGIS Online. Sounds simple, right? Well, not exactly. Let’s talk about relationship classes – those clever connections that tie different datasets together based on shared fields. They’re super useful for keeping your data consistent and making it easy to navigate between related bits of information. Think of it like this: you’ve got a map of campgrounds, and another showing all the individual campsites. A relationship class lets you click on a campground and instantly see all its campsites. Neat, huh?

Here’s the rub: QGIS, as awesome as it is, doesn’t directly create relationship classes that ArcGIS Online plays nicely with. It’s a bit like trying to plug a European appliance into an American outlet – it just won’t work without an adapter. You can’t simply build the relationship class in QGIS and expect ArcGIS Online to recognize it. Bummer, I know.

But don’t throw in the towel just yet! There are ways to make this work. You just need a slightly different approach.

First, the most straightforward method: ArcGIS Pro is your friend here. Seriously, it’s the key. You’ll need to use it to actually create the relationship class within a geodatabase. Think of QGIS as prepping the ingredients, and ArcGIS Pro as cooking the meal. You can still use QGIS to clean and massage your data, then bring it into ArcGIS Pro for the final step. Once the relationship class is set up in Pro, you can happily publish it to ArcGIS Online.

Another option involves FME (Feature Manipulation Engine). I’ve used this myself on a few projects, and it’s a lifesaver. While FME can’t create relationship classes from scratch, it’s a champ at populating them. You’d still need ArcGIS Pro to create the initial structure, but then FME can take the data you’ve been working with in QGIS and pump it into the relationship class. It’s like having a data assembly line. Remember, you’ll need the ArcGIS Data Interoperability extension to get access to FME.

For the truly adventurous (and those comfortable with code), there’s the ArcGIS Online REST API. Fair warning: this is definitely the advanced route. You can technically use the API to add and delete relationship classes in a hosted feature service, but only if the related table and feature layer are in the same service. Honestly, unless you’re a seasoned API wrangler, I’d steer clear of this one. It’s easy to accidentally mess things up.

Back in the QGIS world, you can fake relationships with joins and relates. They won’t be true relationship classes in the ArcGIS sense, but they’ll let you connect data within your QGIS project. Just remember, these connections won’t magically transfer when you upload to ArcGIS Online. They’re more for your own visualization and analysis within QGIS.

One last tip I picked up the hard way: GlobalIDs are your best friends. When you’re setting up your relationship, grab the GlobalID of the parent feature and stick it into a GUID field in the child feature class. Trust me on this one – avoid writing GlobalID to GlobalID directly, as editing the GlobalID field is a no-go. Instead, create an extra GUID field to store the GlobalID for the relationship.

A few things to keep in mind:

• You’ll need at least a Standard license of ArcGIS Pro to create relationship classes.
• Relationship classes live inside geodatabases. They’re picky that way.
• Relationship classes can enforce data integrity, which is a fancy way of saying they can automatically delete related records if you delete something in the main table. Use this power wisely!
• Arcade, the expression language in ArcGIS Online, isn’t always great at directly accessing related records across relationship classes. Just something to be aware of when you’re building your web maps.
• ArcGIS has its limits. Recursive relationships and complex primary/foreign keys aren’t supported. Keep it simple.

Okay, let’s walk through a basic example, assuming you’re using ArcGIS Pro to create the relationship class:

So, while QGIS can’t directly create relationship classes for ArcGIS Online, it’s still a vital part of the process. By combining the data wrangling power of QGIS with the relationship-building capabilities of ArcGIS Pro, you can get your data online with all its connections intact. It might take a little extra effort, but the end result is worth it – trust me!