  Clustering statistics are compared in the Automatic Plate Machine (APM) and
the Edinburgh/Durham Southern Galaxy Catalogue (EDSGC) angular galaxy surveys.
Both surveys were independently constructed from scans of the same adjacent UK
IIIa--J Schmidt photographic plates with the APM and COSMOS microdensitometers,
respectively. The comparison of these catalogs is a rare practical opportunity
to study systematic errors, which cannot be achieved via simulations or
theoretical methods. On intermediate scales, $0.1^\circ < \theta < 0.5^\circ$,
we find good agreement for the cumulants or reduced moments of counts in cells
up to sixth order. On larger scales there is a small disagreement due to edge
effects in the EDSGC, which covers a smaller area. On smaller scales, we find a
significant disagreement that can only be attributed to differences in the
construction of the surveys, most likely the dissimilar deblending of crowded
fields. The overall agreement of the APM and EDSGC is encouraging, and shows
that the results for intermediate scales should be fairly robust. On the other
hand, the systematic deviations found at small scales are significant in a
regime, where comparison with theory and simulations is possible. This is an
important fact to bear in mind when planning the construction of future
digitized galaxy catalogs.
