Converting shape length/area data to latitude/longitude

Question

I am attempting to import publicly available shapefile data from http://gis.utah.gov/data/boundaries/zip-codes/ into Tableau for a data visualization project.

Unfortunately, the .shp file and .gdb database that are available for download include only the shape length / area for each of the Utah zip codes.

My goal is to convert these from the current NAD 1983 UTM 12N (EPSG: 26912) format into latitude / longitude coordinates that can be read into Tableau.

I am using QGIS 2.0.1.

Answer 1

The layer is provided as a polygon so you'll need to convert the polygons to points and calculate the XYs of each point.

• Enable 'on the fly' CRS projections in Project Properties
• Ensure that the Selected CRS is the CRS you want to project the data to
• Add vector layer
• Right click layer and "Save vector layer as..."
• Select the CRS you want the layer exported to
• Save layer and re-add the layer to the project
• Convert the polygon to points using Vector-->Geometry Tools-->Extract nodes
• Ensure the points layer is added to the project
• Open Attributes table for point layer
• Toggle editing mode on
• Open field calculator
• Add two new calculated fields using the $x and $y funcitons under Geometry for each respective field
• Save edits and toggle off edit mode

This should give you a point file with the vertices for each polygon and the respective calcualted X and Y values for each point in the chosen CRS.

Answer 2

I created some videos that take you through the entire process of taking a shape file, bringing it into QGIS, exporting the geometry data, converting it into Tableau format, and then loading it into Tableau.

http://www.excelacom.com/resources/blog/tableau-geospatial-reporting-made-easy

Answer 3

I'm not aware which format is needed for importing into Tableau. One human-readable standard format is Well-known Text (WKT). It's just a list of coordinates with defined syntax and can be converted into any format you need with some simple scripting.

On reprojecting to geographic coordinates: Reprojecting vector layer in QGIS?

On exporting a text file with vertex coordinates in WKT: Create a csv with geometry as WKT in QGIS (and choosing the field delimiter)