[Qgis-user] Precise area calculation with CRS 4326 (+ formula)

[Gabor Szakacs]

Hi there,
I would like to ask for your opinion and help with 2 questions.
1) is CRS 4326 suitable to make precise area calculations of agriculture
field boundaries that vary from 2 to 100ha for the 2nd decimal of a hectare?.
I am aware that CRS 4326 is supposed to have relatively precise area
calculation at the equator and the higher the latitude, the less precise
the area calculation is. But we ran a test in QGIS and outside QGIS with
Python code and benchmarked around 30K fields from North America, South
America and Europe with relatively high latitudes (Canada and Finland). The
avg area difference of the sum of all fields was in the 9th decimal of a
hectare between area calculation with CRS 4326 and area calculation with
regional equal area CRS for each region. Even Canada and Finland had that
area difference of a  9th decimal. Therefore we concluded that CRS 4326 is
suitable for precise area calculation for 2 decimals of a hectare for
agriculture fields, independently of the latitude. Are we on the right
track? It seems that QGIS and Python use formulas that correctly convert
degrees into metric area calculation and minimize the effect of different
latitudes. Any kind of insights would be greatly appreciated.
2) We would like to know which formula is being used in QGIS to do the area
calculation... Does someone know and could share the formula with us ?

Thank you for your attention.
Best,
Gabor

-- 


Dr. Gabor Szakacs
Geospatial Analyst in Regenerative Agriculture

+55 11 989319305

gabor.szakacs at agreena.com

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