[Bf-python] a geoToUTM() function in a bpy module ?

[Campbell Barton]

Hi jerome, such functionality is indeed handy, but think it belongs in
its own module,
perhaps "bpy_extras.geospatial_utils"

./release/scripts/modules/bpy_extras/geospatial_utils.py

Also, wouldn't it make sense to have a function to do the reverse conversion?,
geo_to_utm() / utm_to_geo()

If you don't have time to do this, its fine, but could add in a
comment that its a  TODO.

On Mon, Sep 10, 2012 at 7:16 AM, jerome <jerome.le.chat at free.fr> wrote:
> Hello,
>
> I'm currently programming things about city generation for a BGE project
> I have.
> open street map is a really valuable input for such need, as you know I
> suppose,
> since you can retrieve a lot about city geometry worldwide, and generate
> from it in Blender.
>
> in a recent commit I updated a bit the osm importer to add a better
> projection from lat/lon to blender units.
>
> I think this function, or an equivalent one, should be part of the bpy,
> maybe in mathutils.geometry, or a more suitable location as you wish :
>
> it's really a multi usage function.
> this could help to bridge with the osm community,
> and with architects too.. for now the ones I know are a bit reluctant to
> Blender but I'm hardly working on it, BGE helps a lot actually.
>
> the tests I'm doing with lxml xml parser are very conclusive to read
> write huge osm or extended osm quickly.
> by extended I mean extra tags about height, uvs,utm coords. a kind of
> .bosm format I'm writing.
>
> anyway here's the proposed function, consider it copyleft.
> sorry if my proposal does not respect blender guidelines, but I really
> have no time left :s
>
> regards,
>
> Jerome / littleneo
>
>
> (from math import radians, sin, cos, tan, sqrt)
>
> # given lat and longitude in degrees, returns x and y in UTM (1 KM = 1
> BU ) .
> # accuracy : supposed to be centimeter. community feedback needed.
> # looks ok so far
> # http://fr.wikipedia.org/wiki/Projection_UTM
> # http://fr.wikipedia.org/wiki/WGS_84
> # http://earth-info.nga.mil/GandG/publications/tr8350.2/wgs84fin.pdf
> #
> http://geodesie.ign.fr/contenu/fichiers/documentation/algorithmes/alg0071.pdf
> # wiki is your friend (don't ask me about math Im just a writing monkey.)
> # jerome.le.chat at free.fr
> def geoToUTM(lon, lat) :
>
>      # if abs(lat) > 80 : lat = 80 #wrong coords.
>
>      # UTM zone, longitude origin, then lat lon in radians
>      z = int( (lon + 180)  / 6 ) + 1
>      lon0 = radians(6*z - 183)
>      lat = radians(lat)
>      lon = radians(lon)
>
>      # CONSTANTS (see refs.)
>      # rayon de la terre à l'équateur
>      a = 6378.137
>      K0 = 0.9996
>      # flattening consts
>      f  = 0.0033528106647474805  # 1 / 298.257223563
>      e2 = 0.0066943799901413165  # 2*f - f**2
>      e4 = 4.481472345240445e-05  # e2**2
>      e6 = 3.0000678794349315e-07 # e2**3
>
>      # lat0. 10000 for South, 0 for North
>      N0 = 10000 if lat < 0 else 0
>
>      A = (lon - lon0) * cos(lat)
>      C = (e2 / (1 - e2)) * cos(lat)**2
>      T = tan(lat)**2
>      vlat = 1 / sqrt( 1 - e2 * sin(lat)**2 )
>      slat = (1-(e2/4)-((3*e4)/64)-((5*e6)/256))*lat -
> (((3*e2)/8)+((3*e4)/32)+((45*e6)/1024))*sin(lat*2) + (((15*e4)/256) +
> ((45*e6)/1024) )*sin(lat*4) - ((35*e6)/3072)*sin(lat*6)
>      E = 500 + (K0 * a * vlat) * (A + (1-T+C)*((A**3)/6) + (5 - 18 * T +
> T**2) * ((A**5)/120) )
>      N = N0 + (K0 * a) * ( slat+vlat*tan(lat)* (A**2/2 +
> (5-T+9*C+4*C**2) * (A**4/24) + (61-58*T+T**2) * A**6/720) )
>      return E,N
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-- 
- Campbell