  We introduce a weighted ellipse fitting routine to measure Debye Scherrer
rings acquired on 2D area detectors and demonstrate its use in strain
determination. The method is relatively robust against incomplete rings due to
low number of grains in the diffraction volume (spotty rings), or strong
texture (intensity depletion in some azimuths). The method works by applying an
annular mask around each diffraction ring and fitting an ellipse, using all
pixel positions and their diffracted intensity as weights in the minimisation.
We compare this method to the more popular cake integration method, and show
that the weighted ellipse method works when the cake integration method fails
or works poorly. The lattice strain sensitivity from spotty diffraction rings
is in the order or 2E-5 or better. The algorithm has been made available for
public use and works with 2D diffraction patterns acquired in a laboratory
scale XRD equipment, TEM or a synchrotron.
