[HOT] open geology map

Charlotte Wolter techlady at techlady.com
Sat Mar 14 17:38:41 UTC 2015


         I agree with most of your points and would like to add that 
surface geology is a highly specialized field requiring a great deal 
of expertise. I'm a geology buff myself, and there is no way I would 
attempt to map that. Also, there often is strong disagreement among 
geology professionals about the nature and dating of rock units, 
disagreements that make some of our set-tos about how to code sound trivial.
         Also, there generally is a lot of local information about 
landslides and tsunami risk, courtesy of the USGS, though sometimes 
it is ignored. In Los Angeles, tsunami-prone areas are signed along 
major roads, as are the areas subject to debris flows. The recent 
deadly landslide in Oregon was in an area known to experience 
landslides, but apparently the risk was not widely publicized.
         Tsunami risk, perhaps, could work as an overlay, and I 
believe that data is available from the USGS.
         But, generally, I think this whole area may be too technical 
for widespread application in OSM, even though I would enjoy seeing it.


At 05:59 AM 3/13/2015, you wrote:
>I think this suggestion belongs more on the general OSM talk or 
>tagging list than on the HOT list, but anyway.
>There are already a number of ways to tag surface, like surface=*, 
>natural=*, landuse=*, landcover=*, ... Just read the wiki about 
>those (f.e. 
>There's also a convention in OSM about sub-tagging. F.e. you could tag
>natural=rock + rock=sandstone
>Thus I guess most of what you want is already possible in OSM. You 
>should only try to add a few more specific conventions (f.e. about 
>the types of rock).
>I probably don't really get your 3D attempts, but the general 
>concensus is that it's hard to get in certain places, and thus you 
>can't make a uniform map of heights or angles. As such, OSM contains 
>no height or slope data (apart from the elevation of some peaks), 
>but leaves this to professionals (such as the NASA). It isn't so 
>hard to extract a general slope from good precision elevation data, 
>so there's no point in including it directly in OSM data (with the 
>right preprocessor, it can get rendered on the map anyway).
>So that doesn't belong in OSM, but it isn't the biggest problem IMO. 
>The biggest problem I see in your attempt is ignoring that OSM is a 
>crowdsourced effort. For crowdsourcing, you need a crowd, and that 
>crowd is most easily found in populated places. Your effort seems to 
>focus on areas with a low population (a city isn't very vulnerable 
>for a landslide). But sadly, there's no crowd around there, so the 
>most we would be able to do is some mapping from aerial pictures. 
>This shouldn't hinder you from starting the project, but you 
>shouldn't have very high expectations from it.
>2015-03-12 22:03 GMT+01:00 Hazel <<mailto:hlhj2 at srcf.net>hlhj2 at srcf.net>:
>Dear All,
>Can we again discuss putting geological data into OSM? Specifically, 
>I'd like a recommended way to tag fault lines and surface geology polygons.
>This e-mail assumes the reader knows nothing of geology, apologies 
>to everyone else.
>First, the usecase: geological data saves lives in natural 
>disasters, it is useful for common activities like agriculture, and 
>it is interesting in its own right. It can also be usefully 
>collected by amateurs.
>I am not suggesting that OSM should produce disaster risk maps, or 
>recommendations for farmers. I am saying OSM could collect the data 
>that would allow experts to quickly and easily make these things.
>Using OSM contours, they can work out areas of flood risk and 
>tsunami escape routes. Using contours and and basic geological 
>information, they can work out areas of landslide risk (landslides 
>kill more people than volcanoes or floods or earthquakes, but they 
>kill a few dozen at a time). If we map faults, they'll know more 
>about where earthquakes are likely to happen (you know the photos of 
>roads after earthquakes, offset by a few centimeters? The fault is 
>the plane where the offset happens, and earthquakes use the same 
>faults over and over again). If you map areas of shallow bedrock vs. 
>unconsolidated sediment, you know which areas may suffer soil 
>liquifaction in an earthquake.
>soil liquifaction
>Technical infodump:
>To make a geological map, you map areas with similar surface rock or 
>sediment2. You describe them (anything from field IDs like "greenish 
>rock #2" to detailed technical descriptions) and give them proper 
>names (e.g. "the Tunbridge Wells Sand Formation").
>Having mapped the boundaries between different rock types, you can 
>also trace faults and the line of folds in the rocks. These all 
>obviously exist in 3-D, but are usually represented on 2-D maps. 
>Just mapping the 2-D trace is enough for many purposes.
>If you want to add more information about the third dimension to a 
>two-D map, there are conventions for that. You specify a line (along 
>the axis of the fold, or on the steepest line down the fault plane 
>or boundary plane). You map the direction of this line. Then you 
>measure the angle between the line and the horizontal, and write in 
>on the map (next to standard symbols: for a plane, a T-shape, and 
>for a fold axis, an X with two or three of the lines turned into 
>arrows pointing in the two or three downhill directions).
>Planes on either side of a fold:
>This is actually fairly easy to explain in 3-D, but not in 2-D, and 
>I don't know of a good video. We could make one.
>Let's look at the Weald area of the UK, since it is well-mapped.
>"Lower Cretaceous" and "Upper Jurassic" describe age (lower means older)
>"rocks", "chalk" and "sandstone" describe rock type
>"sands" and "clays" describe sediment type
>"Purbeck Beds", "Ashdown Sand Formation" and so on are proper names 
>of groups of rocks/sediments. These names are hierachical, like 
>taxons, and are in databases (for the Chalk Group that forms the 
>White Cliffs of Dover: 
>The cross-section may help make the 2-d map make sense.
>To see how faults and folds (synclines/synforms, that sag, and 
>anticlines/antiforms, that hog) are mapped as lines, see this map:
>(just gives rock ages, not type).
>Faults are usually much more obvious on small-scale maps than they 
>are on this map.
>For sediments, there exist multiple soil classifications, with 
>mappings between them, and OSM could support them all, but the 
>classes we have (sand, gravel...) would be enough to start with.
>QGIS is increasingly used for geological mapping, so it works 
>increasingly well with many other geological tools. QGIS is already 
>well-integrated with OSM. The barrier for geologists new to OSM to 
>upload their maps is therefore low. Classes of students could do it.
>End infodump, requests for clarification and corrections welcome.
>Could anyone suggest a set of minimal changes that would make it 
>possible to enter data like this? As I said, just having a 
>recommended way to enter a surface geology polygon, a geological 
>contact line (between two polygons), and a fault line (with optional 
>dip direction and inclination) would be very useful.
>Pseudo-3-D perfection would also allow keeners to input the contact 
>between two rock formations (line, with dip direction and 
>inclination) and input folds (line, with dip inclination), but this 
>can also wait.
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Charlotte Wolter
927 18th Street Suite A
Santa Monica, California
techlady at techlady.com
Skype: thetechlady

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