October Meetup Minutes

18 Oct 2015

The Puget Sound QGIS user’s group met Tuesday October 13th at the Richmond Beach Library.

We had seven members in attendance and opened the meeting with a discussion of our large membership versus the small attendance, and where we could get our meetings out of Shoreline and closer to members in the south Puget Sound area. The cost of using meetup.com is rising because we crossed the 50 member threshold. We are planning to create a survey about where people would be able to attend meetings and if they are willing to contribute to the cost of meetup.com.

Stu Smith covered several, but not all of the topics he listed in the agenda for the meetup:

Blend Colors Between Two Raster Layers

Stu demonstrated how to add raster data, create a hillshade, and then blend colors between two layers, using a hillshade as an example.

How to Join Attribute Tables in QGIS

Web Sources for QGIS Help

QGIS Tips

Stu Smith, John Murphy, and Paul McCombs have volunteered with topics for the next meetup. Stu is looking for meeting space in Tacoma.

Join and Relate Notes from Stu

QGIS Joins and Relates

PSQGIS meeting, October 13, 2015

JOINS

Joins are either 1:1 or Many:1. Same with ArcMap

Joins are made via Layer Properties > Joins

After joining, the target table will display NULL values everywhere when you try to sort any of the fields. Solution: close the output table and then reload, subsequent sorts will be OK. Even subsequent joins will not require a reload.

Prefixes can be added to the output table’s join field names, so that they are easily identifiable after the join. This is done in the Add Join dialog box, “Custom field name prefix”. ArcMap does not provide for custom prefix names; only the join table name is used as a prefix.

At 2.10 you can edit the join properties, via Layer Properties > Joins > pencil button. The resulting changes are dynamic, reflected immediately in the output table’s display. Not available in ArcMap.

A single individual join table can be simultaneously joined to multiple target tables.

Joins cannot be chained (join table joined to target table 1, which in turn is joined to target table 2)

Outer and Inner joins:

Outer joins:

Inner joins:

Selections:

Selections made prior to joining:

Selections made after joining:

Filters (aka ArcMap Definition Queries):

Filters made prior to joining:

Filters made after joining:

RELATES:

Relates are 1:Many (same as Arcmap)

Use the Relations tool

a) Create the relation:

b) Then use the QGIS Identify tool. ArcMap uses either the geometry select or attribute select.