Tag Archives: qgis

Map Club — WORKSHOP — Introduction to QGIS

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Last Friday, Map Club embarked upon its second workshop of the semester. This time, we focused on QGIS, a free and open source geographic information system that offers powerful tools for data editing, viewing, and analysis. Participants learned how to import shapefiles into the interface, explore data using the attribute table, and visualize land use in Manhattan with public building footprint data. 

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From top: zoom to layer, attribute layer, land use map, Daniel Chi Cook

This coming Friday will be a free-form hack session on CartoGrid, a grid-based cartogram generator. Hope to see you there!

Sign up here if you would like to receive updates on future Map Club sessions. For this session’s resources and materials, visit the Map Club Github repository.

Map Club, Session 03 — Introduction to QGIS (PLUS: Buttons!)

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By popular demand, Map Club dove into a structured exploration of QGIS this week. QGIS is a free and open source geographic information system that offers powerful tools for data editing, viewing, and analysis. In contrast to previous sessions, this session focused on a few key areas: importing and exporting different file types, re-projecting raw data, and geocoding a list of locations using the MMQGIS plugin.

Attendees worked on completing an introductory projection tutorial, as well as using MMQGIS to extrapolate lat/lon coordinates from a list of place names.

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In other exciting news: Map Club now has official swag! Swing by one of the two upcoming summer sessions to pick up your own marker, terrain, or logo button.

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Next week, we’ll explore Mapzen, an open, sustainable, and accessible mapping platform.

For this session’s resources and materials, visit the Map Club Github repository.

Mapping Voting Rights Act Section Five Locations

This summer, a couple of us in the DSSC have decided to sit down and learn Leaflet & D3. We'll post some of the maps we make in the blog throughout the summer.

I'm grateful to Peter Leonard, the Librarian for Digital Humanities Research at Yale for getting me started on Leaflet at the NYPL Maps Hack 2013 organized by NYPL Labs.

As an exercise, I decided to map out the places no longer covered by the recent Supreme Court decision (PDF) on section four of the Voting Rights Act.

I took the tables on the Dept of Justice section 5 covered jurisdictions page, joined them together with boundaries from the US Census Bureau's TIGER/Line, simplified the shapefiles in QGIS (removed several fields too), exported to GeoJSON and brought the layers into Leaflet.

The map is sitting at a temp location until the bugs get worked out and we can include the maps in CU Spatial blog posts.

As you can see, it's fairly straight forward and includes some modified (simplified?) code from tutorials on the Leaflet site. The color choices came from ColorBrewer.

One thing I think would improve the map a bit would be to be able to click on the word 'townships' in the legend and have it automatically zoom to Michigan since at the starting scale, both townships are difficult to see (same with the three NYC counties).

Eventually, I'll redo this map in D3 because it'll allow me to use a projection better suited for North America.

Eventually we'll put the data into the Spatial Data Catalog, but for now I'm including a link to zip file containing both the shapefiles & geojson layers without proper metadata and a "use at your own risk" disclaimer. If you use it and find any mistakes, please let us know!

Using OpenStreetMap XML data

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OpenStreetMap is a great resource mostly user created and maintained. The data is free of charge and there are several ways of accessing the data for use in a GIS project.

One of the easiest and quickest ways is to download data from CloudMade in shapefile format, but occasionally not all of the features shown in OpenStreetMap are available in the shapefile download.

An alternative is to download the OSM XML data, open it in QGIS, and if needed, export to shapefile.

To do this, open QGIS and under the Plugins menu, select Manage Plugins and turn on the OpenStreetMap plugin. If it’s not there then you will have to add it from Fetch Python Plugins.

The plugin allows for viewing downloaded OSM XML data, downloading large scale areas directly, and uploading edits you’ve made (account required).

Click on the Load OSM from file icon and navigate to the downloaded OSM XML layer.

Put a check mark next to the fields you want to create (these will only populate if the information is encoded). Keep a check mark next to Use custom renderer if you want to symbolize your data similar to the OSM scheme.

If you need to work with any of the features in shapefile format, right click on a layer and select Save vector layer as, and choose ESRI shapefile from the Format pull down menu if not already selected.

And that’s it!

Intro to GIS

With the new semester, we are offering four Intro to GIS workshops, two in EDS and two at the CUMC Health Sciences Library.

The workshops held in EDS will use ESRI ArcGIS software while the ones at CUMC will use QGIS.

Both will have the same content and similar hands-on exercises just using different software.

The first workshop is next week Friday 1/30 from 10:30 – 12:30pm held in EDS, registration is now open.

All of the workshops are two hours long and give an overview of
–        GIS
–        data models
–        basic spatial analysis
–        projections
–        working with your own data
–        finding data

No prior experience with GIS is necessary to attend, the workshop is meant for those without any experience or would like a refresher on the basics.

GIS Intro at the CUMC Health Sciences Library

Thanks to the work of a terrific librarian who works in the CUMC Health Sciences Library, we now are now able to bring the GIS workshops to the Medical Center campus.

To start off with, we will offer the Intro to GIS workshop but will use QGIS, an open source software instead of ArcGIS which is what we use for the majority of our workshops.

Registration won’t open until one week before, but if you are interested in attending you can register from the EDS workshops page.

If you missed the first Intro workshop that took place in EDS, there’s still room in next week’s Friday 9/19 workshop.