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Explain area calculations on Cadasta #65

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SteadyCadence opened this issue Aug 9, 2017 · 2 comments
Open

Explain area calculations on Cadasta #65

SteadyCadence opened this issue Aug 9, 2017 · 2 comments

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@SteadyCadence
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User Settings to change units.

What technique was used to measure the calculation.
@alukach
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alukach commented Aug 9, 2017 •
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What technique was used to measure the calculation.

How does this look:

Cadasta stores all coordinates as a geography data-type in WGS 84 Lat/Lng (EPSG 4326). Area is determined on a spheroid with units in square meters via PostGIS' ST_Area.

It's a bit more on the technical side but should be enough information so that if someone wants to go further (eg "yeah, but how does the database calculate area?"), they have the resources available to do that.

@SteadyCadence
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For now, we can add this material to "Downloading Data" -- as the area calculated in the export.

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@alukach @SteadyCadence