Weekly Project: Noggin Logger--A Wearable GPS Data Logger

Step 5 Data Crunching

At the conclusion of your journey, pull the fabric liner aside, turn off the power, and remove the SD media card. Use any SD media reader to transfer the files onto your computer. The data is platform independent so you can read and massage your GPS content on any computer that can read an SD media card. You should have at least two files on your properly logged card:

• GPSx.TXT
• GPSCON.TXT

The GPSCON file is used for selecting either NMEA data (i.e., "NORMAL") or KML data (i.e., "KML"). The other file (or, files; files are sequentially numbered GPS1, GPS2, etc. for each activation of the logger's power switch) contains the GPS data. Now it's data crunchin' time. Here are a couple of shortcuts and tricks that you can use with BBEdit for quickly trimming your data fat:

• Delete lines that contain "$GPVTG" - removes all velocity & heading data
• Find/Replace "," with tabs
• Use MS Word for converting tabbed data into a table
• Move/delete columns
• Convert table back to text
• Back in BBEdit, Find/Replace tabs with ","
• Delete Line Prefix "0"
• Insert Line Prefix "-"
• Move those decimals with wildcards

If you'd like to retain as much GPS data as possible and disdain the KML data mode, you can reprogram the GPS Logger V1.1 yourself. Spark Fun Electronics has the firmware and an LPC Serial Port Programmer for getting the job done.