Now, had the cops planted a simple homing device which assisted them in following the suspect around, this ruling might've been different. The data-logging aspect seems to be the big issue here.
According to the article, the police planted a GPS tracker on the car, and then "By combining [the results] with Mr. Jones's cell-phone records, the government was able to paint a picture of Mr. Jones's movements that [proved] that he was involved in drug trafficking."
The court then drew a distinction between "visual surveillance" and "virtual surveillance," ignoring the government's argument that they could have obtained the same information by closely tailing Jones. In other words, police attempts to save time and money by more easily tracking the suspect using a homing device were disallowed by the court.
Bottom line: data logging was not the issue. Nor was the increased accuracy of GPS. Police use of a "homing device" was the gist of the successful appeal.
Personally, I look at this case as one similar to a challenge based on using the NCIC database to search rap sheets to identify suspects based on their MO's instead of hand searching files, or use of computer software instead of visually searching fingerprint records.
The court disallowed the police the use of labor saving technology, and the court was wrong.
And if they'd simply gotten a search warrant, instead of acting like a gang of lawless cowboys, the ruling would've been different.
Oh I see.
Hence what they did to Scott Peterson out in Cali when he was a suspect in his wifes demise.