The pole antenna for the Backpack reader is designed for maximum read range.  This also means that it is difficult to pinpoint the location of a tag since it can be anywhere within a large area near the loop.

The simplest strategy to narrow the scan field is to turn the handle to make the plane of the loop perpendicular to the ground.  This will project a narrow detection field off the front edge of the loop.  Sweep the area with the inverted antenna to locate the tag.

Another solution is to flag the areas where tags are detected then change to a focused field antenna to examine each area closely.  Plans for building one are in the attached PDF.