CRS and Projections: Geographic and Projected CRS (01_12)
This lesson is called CRS and Projections: Geographic and Projected CRS (01_12), part of the Mapping with R course. This lesson is called CRS and Projections: Geographic and Projected CRS (01_12), part of the Mapping with R course.
Transcript
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The biggest thing to take away from this video is:
Don’t use geographic CRS for analysis
If you want to read more about coordinate reference systems, Chapter 7 of Geocomputation with R is a good place to start.
In the video I demonstrate the size of 1 degree of longitude changes dependent on latitude. For a more thorough exploration of this I recommend reading this ThoughtCo article. The mathematics of these calculations is definitely not important for your career as a maker of mapo data visualisations. But, if you’re interested in these things see here for a derivation of the degree length formula
When we used st_buffer() to draw circles around the cities we used this code:
world_cities %>%
top_n(10, pop) %>%
st_buffer(10) The size of the buffer is "10" which equates to 10 degrees in CRS 4326. As we'll see in the next video, CRS 3857 is a good choice for a global projected CRS and if we wanted to draw circles with a radius of 1000km we would use this code:
world_cities %>%
top_n(10, pop) %>%
st_transform(3857) %>%
st_buffer(1000E3) %>%
mapview()Have any questions? Put them below and we will help you out!
Course Content
34 Lessons
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