Source: Map Analysis by Joseph K. Berry (http://www.innovativegis.com/basis/MapAnalysis/Topic11/Topic11.htm#Surface_area)
Does anybody have/know a publicly-available global raster dataset of land surface area with terrain considered (see the attached illustration describing the surface area)?
All I want is, very simply (?), for each grid cell (at 5’ or higher resolution) what’s the land surface area (in ha, for example). Can’t believe nobody has done/published it yet (hey, we’re in the age of 30 m DEM..), but I couldn’t find one – other than some theoretical backgrounds here and there, and the TIN stuff in ArcGIS (Thanks, Kai!).
For mapping crop land globally, we conveniently ignored the existence of slope/terrain (duh..) and simply calculated the grid cell area = f(latitude) – waterbody (or sometimes even included waterbody), assuming most crops are grown in flat surface,, in the grand scheme of things. Besides, I’ve been hearing that we don’t gain much by including terrain in the function (“Don’t sweat the small stuff!”). However, even if that’s true – as we’re getting more serious about socioeconomic variables beyond crop production, I think we really need to be more accurate calculating the grid cell area (and this potentially propagates through all sorts of indicators we’re estimating cell by cell). And,
If I don’t hear from anyone within next couple of weeks, I might just go ahead and scratch my own itch again – but thought worth asking. : )