Say I’ve got a steel-roofed warehouse full of boxes, all over which I hatefully climb with a bar-code reader every so often taking inventory. I see a commercial for UPS (the one with the scruffy guy from “Repo Man”) saying they have smart boxes. I assume that means the boxes themselves have GPS receiver, not just the truck. But the truck has a steel roof?
Every website that says it’s possible, either by amplifying the signals weakened by the roof, or by receiving laser, not radio signals (?) are questionable, since they’re commerical sites selling indoor GPS. (Looks like Boeing bought some, but then again, Boeing are idiots.)
The other sites that dispute this are also questionable, since they seem to have a vested interest in selling Radio Frequency Identification tag systems. But this seems to be one LAN detecting the box instead of another LAN, so the box is somewhere in its vicinity. And my only gained advantage is climbing unencumbered by the bar code reader.
I assume that the boxes themselves do not have any GPS receiver. They either have a barcode which is scanned before throwing the box into the truck, or an RFID tag. The truck has a GPS device which tracks its position and relays this information to the company’s servers. By correlating which boxes are on which truck, they can then determine the location of any given box.
In order for any given box to determine its exact location using GPS, it requires a line-of-sight access to atleast 4 GPS satellites (3 satellites if you are tracking on a 2-D plane only). When a box is indoors or in a shed, typically it does not have line-of-sight access to the sky. Also, the location accuracy provided by GPS is not well suited for inventory management applications.
One way to implement inventory tracking in warehouse (without using GPS) is to create a kind of grid and stack model for tracking, whereby the warehouse is broken up into a grid pattern, say A-D and 1-4. Then, every time a package is placed in grid A1, you scan the barcode and capture the grid location. For all packages in grid A1, you create a stack in your tracking application such that for every package placed on top of an existing package, the stack is incremented and the package is stored at the current stack position. This way you do not need to climb up to the top to scan the barcode since you already know what package is on top of the pile. You need a handheld device with a barcode scanner to implement this. A device like the Symbol MC50 is well suited for such a task, and is used by many companies.
There is a movement to introduce Assisted GPS for applications that require tracking indoors or in areas where line-of-sight to the sky is restricted:
Indoor GPS is possible. There has been a great deal of research and development in improving the sensitivity of GPS receivers so that they can be used for tracking the location of cell phones for 911 service. The latest receivers are much improved (20 dB) over the typical GPS receiver. See http://www.fujitsu.com/emea/news/pr/fme_20040721.html for an example.