Error in distance calculations: RGeo::Error::UnsupportedOperation: Method Curve#length not defined. about rgeo HOT 7 CLOSED

Also...

1.9.2p318 :002 > require "rgeo"
=> true
1.9.2p318 :003 > RGeo::CoordSys::Proj4.supported?
=> true
1.9.2p318 :004 > RGeo::Geos.supported?
=> true

from rgeo.

Also....

1.9.3p125 :007 > Cable.limit(10).last.wkb_geometry.distance(Cable.first.wkb_geometry)
RGeo::Error::UnsupportedOperation: Method Geometry#distance not defined.
from /home/cfrugard/.rvm/gems/ruby-1.9.3-p125/gems/rgeo-0.3.8/lib/rgeo/feature/geometry.rb:483:in distance' from (irb):7 from /home/cfrugard/.rvm/rubies/ruby-1.9.3-p125/bin/irb:16:in

from rgeo.

also seeing the issue in ree 1.8.7

from rgeo.

The problem is, when you use the spherical_factory, a bunch of operations are not implemented. The spherical factory uses spherical geometry to do computations, and the math there can get very complicated. (GEOS, for example, does not provide spherical operations-- it does only planar operations.) Most of the fancy spatial operations are available only in Cartesian coordinate systems.

Now, some operations could get implemented. I'm assuming your geometries are LineStrings. LineString length is not hard to implement on the sphere, and I possibly could get that in place for you. However, the distance between two LineStrings is very complex on a sphere, so unless someone smarter than me feels the urge to help with the nonlinear computational geometry (or I can find a suitable C library), I don't know if that's going to be available.

from rgeo.

They are linestrings. Would this also be the case with points? Most of my
use cases are for small distances, so planar won't kill me, either way.

On Tuesday, March 27, 2012, Daniel Azuma <
[email protected]>
wrote:

The problem is, when you use the spherical_factory, a bunch of operations
are not implemented. The spherical factory uses spherical geometry to do
computations, and the math there can get very complicated. (GEOS, for
example, does not provide spherical operations-- it does only planar
operations.) Most of the fancy spatial operations are available only in
Cartesian coordinate systems.

Now, some operations could get implemented. I'm assuming your
geometries are LineStrings. LineString length is not hard to implement on
the sphere, and I possibly could get that in place for you. However, the
distance between two LineStrings is very complex on a sphere, so unless
someone smarter than me feels the urge to help with the nonlinear
computational geometry (or I can find a suitable C library), I don't know
if that's going to be available.

---

Reply to this email directly or view it on GitHub:
#24 (comment)

from rgeo.

spherical_factory does currently implement distance if both sides are points.

Alternatively, if your objects are small, you could project into a planar coordinate system and do the calculations there, but then you'd have to transform (undistort) your distances.

I'll put it on the to-do list to implement LineString#length for spherical_factory, since that should be easy.

from rgeo.

LineString#length is implemented in the spherical_factory as of version 0.3.9. Closing.

from rgeo.