• About
  • Citations
  • GEO links

jamesgeo.com

~ Everything happens somewhere

Monthly Archives: June 2015

Is there a projection worse than Mercator?

22 Monday Jun 2015

Posted by jmsinusa in Data visualisation

≈ Leave a comment

Tags

map projection, mercator

The Mercator Projection gets a lot of bad press for exaggerating the size of countries near the poles and shrinking Africa. In order to boost its much maligned reputation, I have set out to create a map that’s worse than a Mercator…

I took the worse property of Mercator  – the fact that the horizontal scale varies so much with latitude (ie width of country is exaggerated near the poles), and made a map with only two pieces of information:

1) The width of each country in degrees.
2) The order of the countries, South to North

jamesgeo.com 'worse than Mercator' map. Overseas territories (loosely defined) shown in grey.

jamesgeo.com ‘worse than Mercator’ map. Overseas territories (loosely defined) shown in grey. The y-axis is arbitrary.

20150415_223727_horz2plotThese maps are not to be used for navigation!

51.068785 -1.794472
Advertisements

How to graphically compare the size of two countries

08 Monday Jun 2015

Posted by jmsinusa in Geo data

≈ Leave a comment

Tags

compare countries, CONUS, graphical comparison, postGIS

To overlay two countries, move them so that their centres are over the same point (eg 0, 0). The trick is to make sure that they stay the same size, and don’t get too distorted in the process.

The jamegeo.com country comparison method is:

1. Re-project your country into a UTM zone. This means that you can translate (move) it North or South without enlarging / shrinking the country, or distorting the shape. This only works if your country fits inside one UTM zone… which almost none do.

20150415-conus_step0_wgs84

Step 0: Choose your country (or in this case some of a country)

20150415-conus_step1_utm14n_noutmzones

Step 1: Re-project your data into a UTM zone and move it South until the centre is over the Equator.

2. Move the country until the centre sits on the equator. Expect minor change in shape if your country is too fat for its UTM zone.

3. Re-project into a Equirectangular projection (eg WGS84)

20150415-conus_step2_wgs84

Steps 2/3: Put your data back into a rectilinear projection (eg WGS84). Note that CONUS appears to have shrunk, as this projection emphasises size near the poles. Some distortion has occurred because CONUS does not fit into one UTM zone.

4. Move your country along the equator, which you can do in a equirectangular projection without altering the shape.

20150415-conus_step4_wgs84

Step 4: Move your shape East until it is over (0, 0). You can do this in WGS84 because there is no distortion along the Equator.

5. Rescale (a very little bit) to compensate for any shrinking during stage 2.

6. Combine with another country and be very pleased with yourself.

Testing with Greenland, New Zealand and the Congo.

Testing with Greenland, New Zealand and the Congo.

51.068785 -1.794472

Enter your email address to follow this blog and receive notifications of new posts by email.

Recommended posts

  • How to make a great-circle linestring
    How to make a great-circle linestring
  • How to correct a linestring for the antimeridian (180 longitude)
    How to correct a linestring for the antimeridian (180 longitude)
  • About
    About
  • Airline route maps
    Airline route maps
  • The Ballad of Billy the Kid
    The Ballad of Billy the Kid

Recent Posts

  • 2017 flights
  • Constable and Turner visit Nevada
  • Review of 2017
  • Learning to count (regression)
  • Learning to count (classifier)

Archives

  • January 2018
  • December 2017
  • July 2017
  • February 2017
  • January 2017
  • December 2016
  • November 2016
  • October 2016
  • September 2016
  • July 2016
  • June 2016
  • May 2016
  • February 2016
  • January 2016
  • August 2015
  • July 2015
  • June 2015
  • May 2015
  • April 2015
  • March 2015
  • February 2015
  • January 2015
  • December 2014
  • November 2014
  • October 2014
  • September 2014
  • August 2014
  • May 2014
  • April 2014
  • March 2014

Categories

  • Campaigns
  • Computer vision
  • Data visualisation
  • Geo data
  • Geo problems
  • historical maps
  • Imagery analysis
  • Maths
  • Populations
  • Temporal map
  • Uncategorized
  • UNESCO

Meta

  • Register
  • Log in
  • Entries RSS
  • Comments RSS
  • WordPress.com
Advertisements

Recent Posts

  • 2017 flights
  • Constable and Turner visit Nevada
  • Review of 2017
  • Learning to count (regression)
  • Learning to count (classifier)

Categories

  • Campaigns
  • Computer vision
  • Data visualisation
  • Geo data
  • Geo problems
  • historical maps
  • Imagery analysis
  • Maths
  • Populations
  • Temporal map
  • Uncategorized
  • UNESCO

Archives

  • January 2018
  • December 2017
  • July 2017
  • February 2017
  • January 2017
  • December 2016
  • November 2016
  • October 2016
  • September 2016
  • July 2016
  • June 2016
  • May 2016
  • February 2016
  • January 2016
  • August 2015
  • July 2015
  • June 2015
  • May 2015
  • April 2015
  • March 2015
  • February 2015
  • January 2015
  • December 2014
  • November 2014
  • October 2014
  • September 2014
  • August 2014
  • May 2014
  • April 2014
  • March 2014

Meta

  • Register
  • Log in
  • Entries RSS
  • Comments RSS
  • WordPress.com

Create a free website or blog at WordPress.com.

Cancel