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GIS / Mapping Working Group

The Geographic Information Systems (GIS) / Mapping working group is a network of CUNY students, faculty and staff who are interested in sharing methods and techniques, and finding support from others about ways GIS can be used to further research and teaching.

The GIS/Mapping working group is part of a GC Digital Initiatives program designed to create collaborative communities of Digital Fellows, CUNY-wide graduate students, staff, and faculty to meet regularly and share their areas of interest. The working groups provide a sustained, supportive environment to learn new skills, share familiar skills, and collaborate with both the Digital Fellows and the CUNY digital community.

If you are using Geographic Information Systems or other mapping technologies in your teaching and/or research, or if you are interested in mapping your data, or using GIS technology to analyze/visualize your data, we invite you to join the GIS/Mapping working group.

Peruse our mapping resource bank here: https://commons.gc.cuny.edu/groups/gis-working-group/docs/gis-mapping-resources/

For the Spring 2024 semester, the GIS/Mapping working group will meet in the Digital Scholarship Lab, Room 7414, every other Tuesday from 2-4 p.m. Check out our event calendar for the specific meeting dates. Please stop by!

Spatial Join Issues

  • Hey! Has anyone else had trouble executing spatial joins in QGIS 2.18 Las Palmas? I’ve tried using the MMQGIS Plugin –it freezes–and then used the manual point and ( Vector > Data Management Tools >Join Attributes by Location), and  got a message telling me the operation was unsupported (see attached image) below:

    “unsupported operand type(s) for +: ‘int’ and ‘unicode’ See log for more details”.

    I was using Stata to manage data and my professor suggested that sometimes QGIS has issues reading CSVs created in Stata. But I opened it up and saved it several times and that didn’t work either. Anyone have any idea what the issue might be?

    I also downloaded the new QGIS 3.0 Girona and tried it in there. The MMQGIS plugin didn’t work and the manual spatial join process completed the join, but didn’t have a sum option, which made it useless.

    I eventually managed the spatial join in ARC, but I hate using ARC.

    Any help would be appreciated. Best,
    Kasey

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  • Hi Kasey,

    I tried doing a spatial join with MMQGIS in 2.18 and although at first it seemed it froze, after a few seconds it performed the sum operation just fine.

    I usually run the Vector > Data Management Tools >Join Attributes by Location in QGIS 3 and so far I haven’t run into major issues. I am guessing your professor is right and the problem you are facing might be due to the data. It’s true that GIS software in general can be tricky when importing CSV files …I’m also currently banging my head trying to figure out how to do operations with a massive csv database, so I feel your pain.

    I think you already tried this, but still, just to confirm, have you tried “Saving as” a shapefile and making sure that the layers were both in the same CRS? There is another thing you can try, it might work. Try using the field calculator to create a new column, choose any numeric format and just populate it using one of the fields that is giving you trouble (just type “NAME OF THE PROBLEMATIC FIELD” as the expression, including the quotation marks). Then try doing the spatial join and choose only that new field to do the sum and check if that works.

    These issues are not exclusive to QGIS… I use both Arcmap and QGIS and alternate whenever either of them gives me trouble to do any operation. It’s not ideal but so far it has worked for me.

    Let me know if this helped,

    Best,

    Javier

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