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Subject: [ggl] Questions about Boost.Geometry
From: Dragos Chirila (dchirila)
Date: 2011-05-18 09:40:46

Dear all,

This is my first message on this list, so please excuse my lack of

I am developing a small C++ framework (which I plan to release as
open-source soon), focusing on post-processing of climate datasets. Some
computational geometry is a necessary component (for example, for filtering
data inside a polygon on the sphere). For this component, I am currently
trying to implement a separate library.

However, recently I read about the arrival of Boost.Geometry/GGL in Boost
v1.47, and after trying some of the examples it seems quite exciting.

However, I would like to ask several questions:

1. (Approximately) when will the "official" Boost-version be released? I am
already using other Boost libraries, and my core users would prefer to use a
single, stable Boost package.

2. For an initial version of my software, simple spherical coordinates would
suffice. Therefore, can Boost.Geometry (using the spherical coordinate

a) determine whether a GeoLocation (lon, lat) lies inside a GeoPolygon
(specified as a vector of (lon,lat)-pairs)?

* This is not a problem for my geometric routines, since I can use a
cylinder projection, then compute as in the plane case. But can this be
easily achieved with Boost.Geometry?

b) compute the area of intersection between two GeoPolygons?

* This is actually one of my biggest problems, since my (non-specialist)
solution is to:
- project both GeoPolygons onto a plane cutting the sphere;
- compute the clipping polygon in 2D, then
- project back on the sphere and
- compute the area of the spherical polygon.

This does not feel like a good solution, and has many limitations (depending
on the size of the GeoPolygons, a projection plane might not exist, in which
case I have to divide them and try to repeat the procedure). So, is this
possible (maybe trivial) in Boost.Geometry?

I hope this is the right place for these questions. Any input would be
greatly appreciated!


= Dragos B. Chirila
= Computational Physicist, PhD candidate
= Alfred Wegener Institut Bremerhaven, University of Bremen
= +49-0176-320-57856
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