Welcome to Methods 3, Lecture 3
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Methods 3
managing files
make a folder for each thing you work on
come up with a per-project organization scheme
keep your data together
and name the files appropriately
best for New York area, many city datasets use this
source
for now, try to remember the codes 2263 and 4326
you will encounter projections in three ways in QGIS:
- rendering (making your map look good)
- rendering (making your map look good)
- assignment
- rendering (making your map look good)
- assignment (when QGIS doesn't know which projection the data should be in)
- rendering (making your map look good)
- assignment (when QGIS doesn't know which projection the data should be in)
- overlay
- rendering (making your map look good)
- assignment (when QGIS doesn't know which projection the data should be in)
- overlay (for some calculations)
vector data formats
QGIS automatically reads many vector formats:
QGIS automatically reads many vector formats:
QGIS automatically reads many vector formats:
- shapefiles (.shp)
- GeoJSONs (.geojson)
QGIS automatically reads many vector formats:
- shapefiles (.shp)
- GeoJSONs (.geojson)
- KML (.kml / .kmz)
QGIS automatically reads many vector formats:
- shapefiles (.shp)
- GeoJSONs (.geojson)
- KML (.kml / .kmz)
- OSM (.osm)
CSVs are handy for point data
these are simply text files
comma separated values
QGIS doesn't know what the projection of a CSV is in, so you need to help it out
EPSG:4326
EPSG:4326 is essentially latitude and longitude
if your data is in latitude and longitude, use EPSG:4326
thematic maps
thematic maps focus on a theme or subject
vs reference maps
qualitative vs quantitative
in maps:
in maps:
qualitative → categories
in maps:
qualitative → categories
quantitative → numbers
qualitative thematic maps categorize features' attributes
column to categorize on
change all categories' styles
double-click to change one category's style
turn category on or off
double-click to change how the category appears in the legend
quantitative thematic maps use features' numeric attributes
quantitative thematic maps
aka choropleth maps
choropleth
choro: region
pleth: multitude
how do you make a choropleth?
not that differently from a categorized map!
how do you decide which regions are given which styles?
you make up categories for ranges of values
the Modifiable Areal Unit Problem
the Modifiable Areal Unit Problem
the shapes you use can influence the way your data looks without changing the data
sometimes it will help to export a file to a shapefile before doing calculations
start thinking about methodology
keep a document of steps that you are taking, especially if you change or create data
your future self will thank you