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3.8. CONSIDERATIONS AND NEXT STEPS
CHAPTER 3. GEOGRAPHIC ANALYSIS
error.
Second, it’s not always necessary to create a new file with every single processing step. Some menus will give
you the option to select features or perform operations on features that are ALREADY selected. This allows you to
work with just the features you need from one layer to create a new one, skipping the interim step of creating a new
shapefile of just the features you want to work with.
When we’ve created new layers, we have used underscores instead of spaces when naming files, i.e. tracts_nyc_data.shp.
When naming files it’s best practice to use underscores instead of spaces and to avoid using any punctuation in file
names. This helps to insure compatibility of data across operating systems and to prevent possible errors when
loading or reading data in the software. You should follow the same rules when creating folders to store data. The
name of your file should reflect what it contains; you could include the geographic area it covers, the type of feature,
and possibly a date or number to indicate different iterations of the data.
The QGIS Browser makes managing and working with your files a bit easier. It filters files in your folders so that
only GIS usable files are visible. It also collapses shapefiles to single entries so that it’s easier to see what you have. In
addition to the internal Browser in QGIS Desktop, there is also a stand-alone QGIS Browser application. If you have a
folder with layers and you’re not sure what they are, you can easily use this application to preview them, rather than
adding and layering them all in the map interface. For details on the stand-alone Browser, see the Appendix.
3.8
Considerations and Next Steps
Based on our results in Chapter 3, what would you do next? How would you decide where to locate the shop? What
else would you investigate? Is there anything that we’ve done in this exercise that you would do differently, if you had
to conduct an analysis like this for an actual project?
For more practice, some things to try:
• We counted the number of coffee shops per tract and excluded tracts that have a high number of shops, as
there would be too much competition. Alternatively, we could take a distance-based approach and exclude any
area that’s within close proximity to an existing shop. Re-select tracts using only the demographic data as a
criteria. Then use the buffer tools to measure areas that are within a 1/5 of a mile of the coffee shops. Select
the areas of the selected tracts that are within a 1/3 mile of a subway station, but are not within 1/5 mile of an
existing shop (hint - look at some of the geoprocessing tools to accomplish this).
• Shrink the selection areas by removing the greenspace and facilities from the final areas (rather than simply
overlaying them on the selection areas).
• Try looking at how well each subway station is served by existing coffee shops. You can use the Vector >
Analysis Tools > Distance matrix to calculate the distance from each station to the closest shop, or the average
distance from each station to all shops.
F. Donnelly, Baruch CUNY, 2015
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