[CIG-SHORT] 3d spherical model

[Brad Aagaard]

On 07/22/2014 03:30 AM, Shaoyang Li wrote:
> I am going to make a large-scale model, which the earth curvature should be
> considered. And right now, I have all the geometry in UTM coords.
>
> I am wandering can/how pylith 2.0 handle spherical model and in that case how
> gravity vector should be specified? Thanks a lot.
>
> Best regards,
> Shaoyang

All map projections transform locations onto a flat surface, so they all 
ignore curvature of the earth. An Earth-Centered Earth-Fixed coordinate 
system will do what you want. PyLith uses Proj4 which supports ECEF. 
Additionally, I created a custom version of ECEF in spatialdata called 
CSGeoLocalCart that puts the origin at a point near the surface of the 
earth. Applying gravity in with an ECEF coordinate system will result in 
the direction of the body force towards the center of the earth as 
Charles mentioned.

The properties of CSGeoLocalCart are the location of the local origin:
   origin-lon
   origin-lat
   origin-elev

You can use a Python script to convert coordinates of points from any 
other Proj4 supported coordinate system to this one. For example, you 
will need to generate your mesh in this coordinate system.

Attached is a Python script that converts from geographic coordinates to 
a CSGeoLocalCart coordinate system.

Brad

-------------- next part --------------
A non-text attachment was scrubbed...
Name: geotolocal.py
Type: text/x-python
Size: 1098 bytes
Desc: not available
URL: <http://lists.geodynamics.org/pipermail/cig-short/attachments/20140722/ea8e77a4/attachment.py>