GPS2CAD (US$395) is meant for collecting data from the field (defined as "outside the office," and not specific to strawberry fields) when high precision is not necessary. It interfaces with lower-cost GPS units, such as the ultra-cheap (under $100) Garmin eTrex.
The software extracts points from the GPS, translates coordinates, and displays the result in AutoCAD and other CAD software. Download a demo version from GPS2CAD.com.
What the Web site doesn't mention is the data cable: units like the eTrex have a proprietary connector that you can get from Garmin (for US$38) or cheaper from third parites. (Can you tell I own an eTrex?) I got mine from GPS Centeralfor CDN$28 (about US$24).