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I have polygons of countries with its administrative divisions, I would calculate the areas of each division in a country accurately.

I got the bounding boxes for each country, then I divided its width (longitudely) by its height (latitudely).

If the

  • ratio = 1, the country extends equally South-North as West-East
  • ratio < 1, it extends West-East
  • ratio > 1, it extends South-North

But I made my own criteria:

  1. If the ratio < 0.7, I used an Albers equal-area projection +proj=aea with the 1st SP parallel is 1/6 degree below the northernmost latitude of the country, and the 2nd SP is 1/6 degree above the southernmost latitude.
  2. If the ratio is between 0.7 and 1.3, I used Lambert azimuthal equal area +proj=laea centered at the center of the bounding box.
  3. If ratio > 1.3, I used transverse cylindrical equal-area +pro=tcea with central meridian is at the center meridian of the country and k_0=0.9996

My question Would someone approve it to me, that it lets me get accurate areas relatively better than a projection for the whole continent or the whole world, or isa it boring time taking method?

closed as primarily opinion-based by Vince, whyzar, MaryBeth, Erica, csk Dec 5 '18 at 20:09

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

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    1) You need to decide what precision you are interested in, to square km, square m, square cm, square mm :-), 2) it is not clear what the source projection you have identified the shape and size of the States, they are all different projections; 3) would you like to calculate the exact area of the States with regard to elevation +another accuracy in height; 4) Knowing the shape of States, I would choose one or two equal-area projection and bore their original dates, for example, the centroids of each state, and then calculated its area, in any case, continue with your experiments... – Cyril Dec 5 '18 at 11:11
  • My precision would be sufficient in sq.meter, I think, I would have large difference in area for large countries (e.g. Russian Federation) if I follow my criteria, bcz of its large administrative divisions (for example Sakha Republic is so large) but for european countries is better – user9322960 Dec 5 '18 at 11:25
  • In order to perform the calculation with such accuracy, you must have the original cartographic data with an accuracy of at least 1:10,000 scale on the whole Earth, a cheerful picture is obtained... – Cyril Dec 5 '18 at 11:34