  Photometric wide-area observations in the next decade will be capable of
detecting a large number of galaxy-scale strong gravitational lenses,
increasing the gravitational lens sample size by orders of magnitude. To aid in
forecasting and analysis of these surveys, we construct a flexible model based
on observed distributions for the lens and source properties and test it on the
results of past lens searches, including SL2S, SuGOHI and searches on the
COSMOS HST and DES fields. We use this model to estimate the expected yields of
some current and planned surveys, including Euclid Wide, Vera Rubin LSST, and
Roman High Latitude Wide Area. The model proposed includes a set of free
parameters to constrain on the identifiability of a lens in an image, allowing
construction of prior probability distributions for different lens detection
methods. The code used in this work is made publicly available.
