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I am a decent R programmer and statistician, I am able to work with data sets pretty well. I am less familiar with GIS tools, but if given a shapefile I can certainly plot political borders and differently-colored geographies with the mapping packages in the r language. I am motivated to teach myself another program for this project - like QGIS or Python - if this is beyond r's capabilities.

I have a pretty awesome woodworking project in mind, but I am not sure of a suitable data source, and I seek guidance about how to get topographic maps that do not end at sea level. I just bought some brand new chisels and I'm going to buy a big rectangular slab of mahogany to start carving a map into. title of the project: the world without water

I want to print a cross-sectional / overlay that would have been used to make these maps, except a worldwide version. I apologize if that's the wrong terminology.

My woodworking idea is to relief carve -- Google image search -- a map of the world from the tallest mountains down to the Mariana trench. that's 9,000m above sea level to 10,000m below sea level. If I go by 500 meter intervals, that is exactly 39 cross-sections of the topography of earth that I would have to carve. cross-section is the important term here, because for what I am trying to do, I need the entire earth's landmass at or below a certain height.

So for example: cross section #1 would be landmasses that round up to 9,000m instead of rounding down to 8,500m. this is exclusively mount Everest, since K2 rounds down to the cross-section map at 8,500m. that means I should start carving my block of wood everywhere except the peak of mount Everest.

according to Wikipedia, the second, third, fourth, and fifth highest mountains are all closer to 8,500m than they are to 8,000m -- so they would all be left alone for the second iteration of the carving.

This process continues - where I carve one 500m layer of earth at a time - until I hit the bottom of the Mariana trench, 37 cross-sections later.

to re-phrase: cross-section map #1 should show all points on earth lower than 8,750m, cross-section map #2 should show all points on earth lower than 8,250m, cross-section map #3 should show all points on earth lower than 7,750m, and this should keep going down until the deepest point.

I know nothing about what USGS data are available, and there's too much of it (all with fancy names) for me to discern what type of map makes the most sense for my idea.

I just want to be able to print these cross-sections out, so I can trace them and carve down layer-by-layer. as someone with minimal knowledge of GIS nomenclature and available data, it's difficult to search around and know what to look for. I seek any advice explaining how to create 39 cross-sectional layers of the earth's surface.

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    It sounds like you want two Digital Elevation Models (DEMs), one of land above sea level, and one of ocean depth, merged. Your biggest issue is likely to be one of common resolution -- we know a lot more (though not all) about land than the sea. The other issue you'll have is with vertical exaggeration -- The difference between the highest and lowest places, when reduced to a bowling ball, would be less than surface imperfections. – Vince Jul 26 '14 at 16:30
  • hi @Vince thanks so much for this! DEMs look like a smart way to do this, but could you point me to specific worldwide+underwater datasets? usgs.gov seems to only have national DEMs.. also, i think this is an answer not a comment..could you make it an answer so i can +1? ;) – Anthony Damico Jul 26 '14 at 17:53
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    You may want to choose a sustainable wood product, as using mahogany will detract from the message you are trying to convey. – Aaron Jul 27 '14 at 15:16
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The ETOPO1 dataset merges topography and bathymetry in one elevation model. Quoting the home page:

ETOPO1 is a 1 arc-minute global relief model of Earth's surface that integrates land topography and ocean bathymetry. It was built from numerous global and regional data sets, and is available in "Ice Surface" (top of Antarctic and Greenland ice sheets) and "Bedrock" (base of the ice sheets) versions. Historic ETOPO2v2 and ETOPO5 global relief grids are deprecated but still available.

You'll probably want to down-sample the arc-minute resolution (21600x10800) to something in the 5 to 15 arc-second range (4320x2160 to 1440x720), retaining the maximum above sea level and the minimum below, so there will be room to learn how to use raster manipulation functions.

You're still going to have an issue with deciding on a value for vertical exaggeration. If it's too small, nothing but Nepal and the larger ocean trenches will be visible, and if it's too large, you'll need to spend a fortune on that block of mahogany.

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