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| bio | website | jasondavies.com |
|---|---|---|
| location | London, United Kingdom | |
| age | ||
| visits | member for | 1 year, 8 months |
| seen | yesterday | |
| stats | profile views | 27 |
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Feb 9 |
awarded | Tumbleweed |
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Feb 2 |
asked | Label datasets with LineString positions |
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Jan 17 |
comment |
Calculating a spherical polygon centroid I found it, and realised you translated it to English, so thank you. :) |
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Jan 10 |
comment |
Calculating a spherical polygon centroid Do you mind providing a reference for the area calculation due to Bessel, too? I can't seem to find it anywhere, and I'm interested in writing a fast (and accurate) spherical polygon area routine. Thanks! |
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Jan 4 |
comment |
How to create an accurate Tissot Indicatrix? How did you compute the orientation of the ellipses? |
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Dec 28 |
comment |
Calculating a spherical polygon centroid Great, thanks for the reference. |
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Dec 27 |
comment |
Centroid of the equator and a point I changed "bottommost" to "southernmost" for clarity. I'm trying to describe how I'm generalising the planar center of mass to a sphere. Do let me know if my intuition is incorrect here! |
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Dec 27 |
revised |
Centroid of the equator and a point s/bottommost/southernmost |
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Dec 27 |
comment |
Centroid of the equator and a point Yes, I'm after the spherical analogue of the planar barycenter, if such a thing exists. This is why I'm unsure about mixing integrals of different dimensions (points, lines and areas). My question is whether it's mathematically consistent to fall back to lower dimensions if there is an ambiguity. (BTW, for the Equator could you also pick a pole for its barycenter? Or indeed any point on the sphere?) |
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Dec 27 |
comment |
Calculating a spherical polygon centroid Can you explain why the position of Jenness' centroids will depend on how a polygon is divided into triangles? I know from @whuber's example that Jenness' centroid calculation is wrong for spherical triangles, but what if a centroid based on spherical triangle medians is used instead? Will this still fail? |
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Dec 27 |
comment |
Centroid of the equator and a point @whuber I've added a couple of paragraphs explaining the physical intuition. Since it's such a rare case, maybe it's safest to just return undefined for mixed geometries, the highest dimensions of which are ambiguous. |
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Dec 27 |
revised |
Centroid of the equator and a point Added a couple of paragraphs explaining physical intuition. |
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Dec 27 |
comment |
Centroid of the equator and a point Agreed; I've already decided to let the user (of my library) decide what to do for a single ambiguous case e.g. equator centroid. In this case I return undefined. My question is whether to also return undefined for [equator, point]. The main use case that I'm imagining is rotation of a globe to focus on the "middle" of a particular feature. It seems reasonable to fall back to lower dimension centroids. I suppose I want to know if this is mathematically/physically consistent, since it's a rare case anyway. |
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Dec 27 |
accepted | How do different GIS systems determine a Polygon's interior? |
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Dec 27 |
answered | How do different GIS systems determine a Polygon's interior? |
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Dec 27 |
accepted | How do I represent the whole Earth as a Polygon? |
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Dec 27 |
answered | How do I represent the whole Earth as a Polygon? |
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Dec 27 |
asked | Centroid of the equator and a point |
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Dec 8 |
revised |
Why might Ordnance Survey codes all be out by 500m? Formatting and clarify resolution comment. |
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Dec 8 |
reviewed | Reviewed Determine density or cover from a raster layer that has been clipped by a polygon |
