Fixed #11948 -- Added interpolate and project linear referencing methods

Thanks novalis for the report and the initial patch, and Anssi
Kääriäinen and Justin Bronn for the review.

docs/ref/contrib/gis/geos.txt

@@ -416,11 +416,36 @@ quarter circle (defaults is 8).
 Returns a :class:`GEOSGeometry` representing the points making up this
 geometry that do not make up other.
 
+.. method:: GEOSGeometry.interpolate(distance)
+.. method:: GEOSGeometry.interpolate_normalized(distance)
+
+.. versionadded:: 1.5
+
+Given a distance (float), returns the point (or closest point) within the
+geometry (:class:`LineString` or :class:`MultiLineString`) at that distance.
+The normalized version takes the distance as a float between 0 (origin) and 1
+(endpoint).
+
+Reverse of :meth:`GEOSGeometry.project`.
+
 .. method:: GEOSGeometry:intersection(other)
 
 Returns a :class:`GEOSGeometry` representing the points shared by this
 geometry and other.
 
+.. method:: GEOSGeometry.project(point)
+.. method:: GEOSGeometry.project_normalized(point)
+
+.. versionadded:: 1.5
+
+Returns the distance (float) from the origin of the geometry
+(:class:`LineString` or :class:`MultiLineString`) to the point projected on the
+geometry (that is to a point of the line the closest to the given point).
+The normalized version returns the distance as a float between 0 (origin) and 1
+(endpoint).
+
+Reverse of :meth:`GEOSGeometry.interpolate`.
+
 .. method:: GEOSGeometry.relate(other)
 
 Returns the DE-9IM intersection matrix (a string) representing the

docs/releases/1.5.txt

@@ -103,10 +103,22 @@ associated with proxy models.
 
 New ``view`` variable in class-based views context
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
 In all :doc:`generic class-based views </topics/class-based-views/index>`
 (or any class-based view inheriting from ``ContextMixin``), the context dictionary
 contains a ``view`` variable that points to the ``View`` instance.
 
+GeoDjango
+~~~~~~~~~
+
+* :class:`~django.contrib.gis.geos.LineString` and
+  :class:`~django.contrib.gis.geos.MultiLineString` GEOS objects now support the
+  :meth:`~django.contrib.gis.geos.GEOSGeometry.interpolate()` and
+  :meth:`~django.contrib.gis.geos.GEOSGeometry.project()` methods
+  (so-called linear referencing).
+
+* Support for GDAL < 1.5 has been dropped.
+
 Minor features
 ~~~~~~~~~~~~~~
 
@@ -379,8 +391,6 @@ on the form.
 Miscellaneous
 ~~~~~~~~~~~~~
 
-* GeoDjango dropped support for GDAL < 1.5
-
 * :func:`~django.utils.http.int_to_base36` properly raises a :exc:`TypeError`
   instead of :exc:`ValueError` for non-integer inputs.