Posts for Tag: map
Antipodes map: What’s on the other side of the Earth?
What is an antipode?
An antipode is a point that is on the exact opposite side of the earth (or other sphere) from a given location. If you drew a line (vector) from your location to the center of the earth and continued that line until it emerged from the other side of the earth’s surface, that point of intersection on the other side is the antipode. When I was a kid, people occasionally mentioned “digging a hole to China”. While this is currently impossible for many reasons1Earth’s core is about 6000 degrees C, China is not the antipode for North America (where I grew up). If you grew up in Argentina or Chile, then maybe that would make a little more sense.
The antipodes for most of North America and Europe are in the Indian and South Pacific oceans respectively.
Other examples of antipodes that are both on land:
Instructions:
It should be relatively explanatory, but you find your location by dragging the globe on the left side so that your location is in the center crosshair. The other globe (on the right) will show you the antipode to your location.
You can zoom in and out with the +/- buttons or pinch to zoom on mobile. If you zoom in enough, it will look like a normal two-dimensional web map (like google maps).
Tools:
This interactive visualization is made using the awesome webglearth javascript library. I just discovered this recently after making a number of 2D maps.
Footnotes
Footnotes
↑1 Earth’s core is about 6000 degrees C
Scaling the physical size of States in the US to reflect population size (animation)
States sized to New Jersey’s population density
Choropleth maps are a pretty useful kind of map that colors distinct areas of the map (e.g. states, counties or countries) to reflect different numerical or categorical values. It is useful to show differences across geographic regions. I’ve been making a bunch of these recently (stressed states, bitcoin electricity consumption, college admissions). One of the issues that can be problematic with these maps is that some regions can be very large but only have very few people. If the choropleth map is tracking a intensity value (like CO2 emissions per capita), a large area with a high color value might visually indicate that total emissions (emissions per capita x # of people) is also high. In the US this is reflected in states like Alaska, Montana and Wyoming, which are large but have very few people.
I decided to make a modified choropleth map (updated after learning that it’s called a cartogram) that scales the size of the states to be the proportional to the state’s population. States with larger populations show up as larger. This is equivalent to making each state have the same population density. Since New Jersey has the highest population density of any state in the US (1200 people/square mile), it stays the same size in this map and all the other states shrink, to reflect their lower population density. For example, California has a larger population than NJ (4.4x), but its physical size is about 20x larger. So California is shrunk to about 20% its original size to make its physical size 4.4x the size of NJ.
The states are also colored to show population as well (darker redder colors reflect larger population while yellow/beige reflects small populations).
States sized to California’s population density
Living in California, I decided to make another animation, this time with scaled to the density of California, so some states that are less dense will shrink, while others that are denser will grow. New Jersey grows quite a bit. Because many of the dense Northeast states grow a bit, I had to space them out (manually) so you could still see them otherwise they’d overlap too much.
Data Sources and Tools:
2015 population and population density data comes from Wikipedia and leaflet.js open source mapping library was used to create the maps. State outlines in geoJSON format come from leaflet. Javascript code was used to scale the coordinates of the geoJSON polygons to the appropriate size and animate the map.
Real Country Sizes Shown on Mercator Projection (Updated)
Hover or click on a country to see how much it shrinks from the Mercator projection size.
Check out some other engaging and interactive map dataviz:
I remember as a child thinking that Alaska was as large as 1/2 of the continental US. Later, however, I learned that while it is the largest state, it is actually only about 1/5 the size of the lower 48 states. My son has also remarked that Greenland is very big. And while it is very big, it’s nowhere near the size of the continent of Africa.
The map above shows the distortion in sizes of countries due to the mercator projection. Pressing on the button animates the country ‘shrinking’ to its actual size or ‘growing’ to the size shown on the mercator projection. It was inspired by a similar animation that I saw on reddit and decided I wanted to try to build the same thing.
The mercator projection is a commonly used projection on computer maps because it has perpendicular latitude and longitude lines (forming rectangles). It is formed by projecting the globe onto a cylinder A variant of the was adopted by Google maps, which helped establish it as the informal standard for web-based maps (although Google maps now also uses a globe view, instead of a map projection when zooming out to a very wide view).
Areas far from the equator are distorted in terms of their distances and are shown much larger than they actually are. This is one of the major issues with a projection of a globe onto a cylinder area. This is why Greenland, Russia and Canada shrink so much in height and width in the animation, they are fairly high in latitude in the Northern Hemisphere. Also important is that the closer you are to the poles, the more the distortion when a country is shown on the Mercator projection. Since longitude lines converge at the poles, but are parallel on a Mercator, the closer a part of a country is to the poles, the more that part will get stretched wider relative to a part of a country that is not as close to the poles. As a clear example, see what happens to the southern part of Australia, relative to the northern end. Similarly, the latitude lines also get further apart on a Mercator projection, while on a globe they stay equidistant. This means that the parts of countries that are nearer the poles will get taller, i.e. stretched out from a north-south perspective relative to parts of countries that are further from the poles. You can see this clearly in the northern ends of Russsia and Greenland, where the tops get smushed down.
This next graph shows each country plotted with their actual land area and apparent land area as shown on a Mercator projection. The further the countries are from the 1:1 line the greater the overestimate of their size from the Mercator (also color coded to be red). It is a logarithmic plot showing many different orders of magnitude in country size. The table also shows the top 10 countries whose size is overestimated (and the difference in land area in square kilometers or as a percentage reduction from the size in the Mercator projection).
As it shows, Greenland is the country that has the largest percent difference between its apparent size in a Mercator projection and it’s real size (it’s only about 1/4 of the apparent size). And Russia is the country with the largest absolute difference between these two sizes.
This is the original graph that keeps the shape of the countries exactly the same and just scales the size. This is incorrect because as you move towards the poles the distances between longitude lines decreases. As a result the tops (northern ends) of countries will shrink more than the bottoms (southern ends) of countries in the Northern Hemisphere and vice versa in the Southern Hemisphere.
Old map that changes sizes but incorrectly preserves the Mercator shape
Calculations:
I calculated the area in two ways, one assuming latitude and longitude are rectangular coordinates (i.e. Mercator projection) and the other was the actual area.
The new coordinates needed to draw the “real size” of the countries are derived by calculating the distance between the center of the country and each of the coordinates in the country’s shapefile. As you move towards the poles on a globe, the distance between longitude lines decreases as a function (cosine) of latitude. In a mercator projection, the longitude lines are shown as equi-distant regardless of latitude. In this calculation, we create a new set of coordinates by calculating the distance between the center of the polygon and each set of coordinates and change the coordinates to reflect the shrinking of distance between longitude lines as you head towards the poles.
In the previous version of this animation, I calculated the latitude and longitude coordinates for the outline of the “real” size by modifying the original latitude and longitude by the ratio of these two areas to draw the new smaller, “real” country size.
Data and tools: This visualization was made using the Leafletjs javascript mapping library and country shapefiles (converted to geojson).
Current Bay Area Air Quality
Fires are once again raging in California and air quality in one of the most populated metropolitan areas in the country (the San Francisco Bay Area) is quite poor. This map show current air quality in the Bay Area. For more information see the EPA’s Air Quality website.
AQI colors
EPA has assigned a specific color to each AQI category to make it easier for people to understand quickly whether air pollution is reaching unhealthy levels in their communities. For example, the color orange means that conditions are "unhealthy for sensitive groups," while red means that conditions may be "unhealthy for everyone," and so on.
For more information and additional maps see the EPA’s Air Quality website.
Antipodes map: What’s on the other side of the Earth?
What is an antipode?
An antipode is a point that is on the exact opposite side of the earth (or other sphere) from a given location. If you drew a line (vector) from your location to the center of the earth and continued that line until it emerged from the other side of the earth’s surface, that point of intersection on the other side is the antipode. When I was a kid, people occasionally mentioned “digging a hole to China”. While this is currently impossible for many reasons1Earth’s core is about 6000 degrees C, China is not the antipode for North America (where I grew up). If you grew up in Argentina or Chile, then maybe that would make a little more sense.
The antipodes for most of North America and Europe are in the Indian and South Pacific oceans respectively.
Other examples of antipodes that are both on land:
Instructions:
It should be relatively explanatory, but you find your location by dragging the globe on the left side so that your location is in the center crosshair. The other globe (on the right) will show you the antipode to your location.
You can zoom in and out with the +/- buttons or pinch to zoom on mobile. If you zoom in enough, it will look like a normal two-dimensional web map (like google maps).
Tools:
This interactive visualization is made using the awesome webglearth javascript library. I just discovered this recently after making a number of 2D maps.
Footnotes
| ↑1 | Earth’s core is about 6000 degrees C |
|---|
Scaling the physical size of States in the US to reflect population size (animation)
States sized to New Jersey’s population density
Choropleth maps are a pretty useful kind of map that colors distinct areas of the map (e.g. states, counties or countries) to reflect different numerical or categorical values. It is useful to show differences across geographic regions. I’ve been making a bunch of these recently (stressed states, bitcoin electricity consumption, college admissions). One of the issues that can be problematic with these maps is that some regions can be very large but only have very few people. If the choropleth map is tracking a intensity value (like CO2 emissions per capita), a large area with a high color value might visually indicate that total emissions (emissions per capita x # of people) is also high. In the US this is reflected in states like Alaska, Montana and Wyoming, which are large but have very few people.
I decided to make a modified choropleth map (updated after learning that it’s called a cartogram) that scales the size of the states to be the proportional to the state’s population. States with larger populations show up as larger. This is equivalent to making each state have the same population density. Since New Jersey has the highest population density of any state in the US (1200 people/square mile), it stays the same size in this map and all the other states shrink, to reflect their lower population density. For example, California has a larger population than NJ (4.4x), but its physical size is about 20x larger. So California is shrunk to about 20% its original size to make its physical size 4.4x the size of NJ.
The states are also colored to show population as well (darker redder colors reflect larger population while yellow/beige reflects small populations).
States sized to California’s population density
Living in California, I decided to make another animation, this time with scaled to the density of California, so some states that are less dense will shrink, while others that are denser will grow. New Jersey grows quite a bit. Because many of the dense Northeast states grow a bit, I had to space them out (manually) so you could still see them otherwise they’d overlap too much.
Data Sources and Tools:
2015 population and population density data comes from Wikipedia and leaflet.js open source mapping library was used to create the maps. State outlines in geoJSON format come from leaflet. Javascript code was used to scale the coordinates of the geoJSON polygons to the appropriate size and animate the map.
Real Country Sizes Shown on Mercator Projection (Updated)
Hover or click on a country to see how much it shrinks from the Mercator projection size.
Check out some other engaging and interactive map dataviz:
I remember as a child thinking that Alaska was as large as 1/2 of the continental US. Later, however, I learned that while it is the largest state, it is actually only about 1/5 the size of the lower 48 states. My son has also remarked that Greenland is very big. And while it is very big, it’s nowhere near the size of the continent of Africa.
The map above shows the distortion in sizes of countries due to the mercator projection. Pressing on the button animates the country ‘shrinking’ to its actual size or ‘growing’ to the size shown on the mercator projection. It was inspired by a similar animation that I saw on reddit and decided I wanted to try to build the same thing.
The mercator projection is a commonly used projection on computer maps because it has perpendicular latitude and longitude lines (forming rectangles). It is formed by projecting the globe onto a cylinder A variant of the was adopted by Google maps, which helped establish it as the informal standard for web-based maps (although Google maps now also uses a globe view, instead of a map projection when zooming out to a very wide view).
Areas far from the equator are distorted in terms of their distances and are shown much larger than they actually are. This is one of the major issues with a projection of a globe onto a cylinder area. This is why Greenland, Russia and Canada shrink so much in height and width in the animation, they are fairly high in latitude in the Northern Hemisphere. Also important is that the closer you are to the poles, the more the distortion when a country is shown on the Mercator projection. Since longitude lines converge at the poles, but are parallel on a Mercator, the closer a part of a country is to the poles, the more that part will get stretched wider relative to a part of a country that is not as close to the poles. As a clear example, see what happens to the southern part of Australia, relative to the northern end. Similarly, the latitude lines also get further apart on a Mercator projection, while on a globe they stay equidistant. This means that the parts of countries that are nearer the poles will get taller, i.e. stretched out from a north-south perspective relative to parts of countries that are further from the poles. You can see this clearly in the northern ends of Russsia and Greenland, where the tops get smushed down.
This next graph shows each country plotted with their actual land area and apparent land area as shown on a Mercator projection. The further the countries are from the 1:1 line the greater the overestimate of their size from the Mercator (also color coded to be red). It is a logarithmic plot showing many different orders of magnitude in country size. The table also shows the top 10 countries whose size is overestimated (and the difference in land area in square kilometers or as a percentage reduction from the size in the Mercator projection).
As it shows, Greenland is the country that has the largest percent difference between its apparent size in a Mercator projection and it’s real size (it’s only about 1/4 of the apparent size). And Russia is the country with the largest absolute difference between these two sizes.
This is the original graph that keeps the shape of the countries exactly the same and just scales the size. This is incorrect because as you move towards the poles the distances between longitude lines decreases. As a result the tops (northern ends) of countries will shrink more than the bottoms (southern ends) of countries in the Northern Hemisphere and vice versa in the Southern Hemisphere.
Old map that changes sizes but incorrectly preserves the Mercator shape
Calculations:
I calculated the area in two ways, one assuming latitude and longitude are rectangular coordinates (i.e. Mercator projection) and the other was the actual area.
The new coordinates needed to draw the “real size” of the countries are derived by calculating the distance between the center of the country and each of the coordinates in the country’s shapefile. As you move towards the poles on a globe, the distance between longitude lines decreases as a function (cosine) of latitude. In a mercator projection, the longitude lines are shown as equi-distant regardless of latitude. In this calculation, we create a new set of coordinates by calculating the distance between the center of the polygon and each set of coordinates and change the coordinates to reflect the shrinking of distance between longitude lines as you head towards the poles.
In the previous version of this animation, I calculated the latitude and longitude coordinates for the outline of the “real” size by modifying the original latitude and longitude by the ratio of these two areas to draw the new smaller, “real” country size.
Data and tools: This visualization was made using the Leafletjs javascript mapping library and country shapefiles (converted to geojson).
Current Bay Area Air Quality
Fires are once again raging in California and air quality in one of the most populated metropolitan areas in the country (the San Francisco Bay Area) is quite poor. This map show current air quality in the Bay Area. For more information see the EPA’s Air Quality website.
AQI colors
EPA has assigned a specific color to each AQI category to make it easier for people to understand quickly whether air pollution is reaching unhealthy levels in their communities. For example, the color orange means that conditions are "unhealthy for sensitive groups," while red means that conditions may be "unhealthy for everyone," and so on.
For more information and additional maps see the EPA’s Air Quality website.
Recent Comments