The elevation is how high a point is above sea level. In a property, alone it says little: two properties at the same height can be completely different. What does change with altitude is the climate, and there the elevation matters a lot.
Every hundred meters you climb, the temperature drops around half a degree. In the high valleys that decides what can be planted and when the first frost arrives; in the Pampas plain, where the entire property is within twenty meters, the elevation is almost a curiosity and what matters is the elevation range.
Where is it measured from?
"Sea level" is not a single thing: the sea rises and falls, and its average height is not the same on all coasts. That is why each country defines a reference and measures against it.
In Argentina that reference is the National Vertical Reference System 2016, established by the National Geographic Institute. The starting point is in Mar del Plata, and from there it spread to the rest of the country with a network of points measured one after another, with millimeter precision. When a writing or a measurement plane says a height, they say this.
What it doesn't say
- The accuracy is about two meters. To compare properties it is enough; to design a drain, no.
- It is a surface model: on native woodland, forest curtains or buildings it returns the height of the crown or roof, not that of soil.
- Each data covers 30 by 30 meters.