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1

Good solutions, another solution to this problem and one that I would have used until I read these other posts would be to create two layers from the same shapefile. The first layer I would symbolize with the color you want to fill and no border outline, then I would set this layer to the transparency you required. The second layer would display all of ...


0

In QGIS Wien, you can click on the color properties and then set the opacity to 0%. The borders will be unaltered.


3

Your main question title indicates you're looking at sea level and coastal areas. But we'll start at the bottom of your question and work backward. Consider lakes and rivers. Many of them may be significantly above sea level, even their bottoms, thus relying on elevation alone in the DEM cannot tell you if an area is water or not. Plus in a DEM large water ...


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Projection matters more than format. If you are not getting enough precision, switch from a UTM projection to something centered more around you area. And if you try float64, you'll do better, but my guess it that you are then shaving yaqs for your use case. If you really want to preserve exact numbers, scale elevation and use ints.


2

The easiest way is to use a raster elevation dataset. If you can't get hold of the one used to create the contours (presuming they weren't done by hand from point data) you can: Open menu Raster/Conversion/Rasterize (Vector to Raster) Choose your contour (level curves) file and a suitable grid size (likely based on the area you wish to work with and ...


3

Try the IEEE 754 Converter http://www.h-schmidt.net/FloatConverter/IEEE754.html. Read the note: Rounding errors: Not every decimal number can be expressed exactly as a floating point number. This can be seen when entering "0.1" and examining its binary representation which is either slightly smaller or larger, depending on the last bit. You can ...


0

How I solved my little problem: 1. Firstly, vectors of required 'cost areas' were created (was trying to do it in GRASS but it's too painful - ended up in QGIS). 2. Then I set appropriate cost values for each of such 'cost area' vectors (by this point I was already working in GRASS; we set cost values by adding new column in the attribute table of each ...


1

An "ellipsoid" is a mathematical approximation of the shape of the Earth. Many different ellipsoids exist, but the two most widely used today are the GRS80 and the WGS84, which attempt to provide a best-fit across the globe. Heights were traditionally referenced to MSL, but with satellite and other technologies, we can often do better in terms of accuracy. ...


4

An ellispoid is a mathematical model of the earth that approximates its three dimensional shape. See this definition. Elevation on top of the ellipsoid is 0, but since it's just an approximation one can be above or below the ellipsoid at any given point. "Elevation above the surface of the ellipsoid" is the distance between the measurement and the 0 value of ...


15

The elevation above the ellipsoid (ellipsoidal height) is the elevation above a mathematical model that approximates the shape of the earth. The current most common one is WGS84. These are the elevations that you'd get from a GPS. Orthometric heights are measured above the geoid or equipotential surface, that is, the surface of equal gravity. MSL is "mean ...


8

The easiest way is to import your points into a format that can be queried with SQL, like PostGIS, SQLite or Shapefile (using OGR). Then you can query: SELECT * FROM [table] a, [table] b WHERE a.[featureid] <> b.[featureid] AND ST_Z(a.[geometry]) - ST_Z(b.[geometry]) >= 200; Or you can query and make lines in one step: SELECT ...



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