Qgis- Merging datasets of similar data without losing attributes

Question

I'm looking for advice on how to compile some datasets that each have a different set of attributes. Each dataset is point data, recorded in one of the two coordinate systems that have been used historically in my area. With each of my six datasets (thousands of points in each file) there are points that are contained in other datasets, as well as some which are unique. The duplicated points may not be exact coordinate matches, as they are observed coordinates, and may not be from the same observation.

I would like to compile these datasets into a single dataset, where each successive attribute table is appended onto the end so no data is lost, but all duplicated entries are merged into a single row/feature. I don't want to calculate a mean, or best likely coordinate, I want it to just add each source layers coordinates, and other fields as new attributes, so I can see the history of each observation.

The result will be a master database that I can then clean up without 6 entries for 70% of the points.

Answer 1

You can use Join attributes by location and Join attributes by nearest - you can run both using Menu Procssing > Toolbox and entering the respective name in the search box.

Answer 2

You can achieve that using table join.

1. Define one of the datasets (layers) as master - the one with best data quality/most details.

2. Create a new attribute with a code that identifies the correspoinding feature from the remaining datasets: like point 5 of master dataset corresponds to point with id=17 of dataset_2, point with id=32 of dataset_3 etc.

3. The make a table join to add the attributes of point 17/dataset_2 and point 32/dataset_3 to point 5 of the master dataset. Open Layer properties of the master layer > Join and add a new Vector Join (see screenshot), joining first dataset_2 and join its id field to the corresponding Target field (named dataset_2 in my case):

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Edit

If you have unique points you want to add to the other layer (your comment), just copy them, switch to the layer where you want to add them > toggle editing > paste them using Menu Edit > Paste Features.