Recently I asked this question:

Why accurate area of all countries cannot be obtained using a single EPSG code, even if it corresponds to an equal-area projection?

It was pointed out in the comments that:

This is more of a "Yes, that's the way it works" than a "Why" issue. If you understood what a projection is, then the answer would be obvious. Unfortunately, GIS SE is an "on-point answer" place, so demanding an "elaborate" answer, when a textbook covers the topic in a chapter or three, makes this too broad for our Focused question/Best answer model.

Would modifying the question so that it asks about textbooks explaining this make it on-topic?


I agree with the commenter you cite, that your question on Main, in its current form, lacks focus because it looks for answers to multiple unmarked questions.

I do not think that asking for a text book recommendation instead will bring it on-topic, because that is likely to result in a list of each text book about projections and coordinate systems that particular users favor and give their opinion on.

To bring your question on-topic I think you should revise it heavily to simply show how you have calculated the area in meters of the same polygon using two equal area projections, and asking why they are not (at least near) identical. That original polygon could be generated in a geographic coordinate system using longitude and latitude values in decimal degrees.


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