does anyone know how to go about converting lat, long, alt to x, y, z where you have an origin for x/y coordinate (specific place in London)? In other words, I have a lat long and alt data and would like to convert the to x,y,z with respect to a specific place, not the Earth center.
For example, lat long is (51.5081° N, 0.0759° W) tower of london with altitude 100 meters and I want to convert my gps lat long to x y z considering the tower of london as the origin.
Assuming you know how to convert lat/lon to earth-centered xyz (for which there are many posts), and assuming your "Tower of London" coordinate system is just a translation of the earth-centered system (ie, your axes are parallel to the corresponding earth-centered axes and oriented in the same directions):
convert the Tower of London lat, lon to xyzTOL
convert the Point of Interest lat, long to xyzPOI
The POI in terms of the Tower of London centered coordinates is:
xyzPOI - xyzTOL
You can set up a local transverse or oblique mercator projection on your origin point using its lon/lat, like described in Using customized Coordinate System in ArcGIS Desktop? In most cases you don't need a rotated CRS, so transverse mercator will do.
If you add the altitude as the z coordinate, you will get the altitude in the transformed system in pyproj with transform. You need to subtract the 100m of your origin point.
