Trying to Append, but not replace

Discussion created by DuncanRager on Apr 5, 2010
I have a large number (~1,000) of shapefiles with point features that represent testing sites. Every shapefile simply represents a certain day. My end goal is to clip each shapefile to a desired region, then reproject those clips.

The problem is that when a testing site recorded no data, no point feature was created, resulting in a a different extent for each shapefile. Now, when I try to batch clip all of these shapefiles, the process stops in error everytime it sees a shapefile with missing test sites. Presumably the extent is completely different, and there is nothing to clip... so ArcMap doesn't like that.

So, to resolve that issue, I took a clip of my desired region with zeroes in the attribute of interest, batch appended it to every one of my shapefiles, and from there I clipped and reprojected. This worked great for the shapefiles that had missing data, but for the ones that actually had those testing site point features, after the append they ended up with two point features with the exact same geometry/coordinates, one with an actual attribute value, and one with a value of zero.

Attached is a visual representation of this problem.

Is there a way to combine the overlapping point features? Or maybe make it so that the pre-existing point features override the appending ones?

If not, is there some other method anyone can think of to get to my end goal?

Thanks so much!