USB gps are now more cheap than rs232 GPS, but i haven't found the system for connect it to a PIC microcontroller, i have only understant that is need a "host usb", but i have found only application for "slave usb" for a PIC.
Some people know as solve the problem ?
USB host is much more complicated than device. Doing hist with a PIC is not possible witout anny support MCU that can run the Host stac. Most USB host controller chips are 32 bit devices designed to work directly on a PCI buss with DMA and all.
On possible solution to this is some "slave host" doing most of the work and then just use the PIC fore some limitied controll. Some circuits to do this is:
cy7c67300 or cy7c67200 or sl811hs from Cypress
ISP1160 or 1161 from philips
UHC124 from oxsemi
search for USB host on forum, there are several other threads talking about this.
if its just for the GPS I would say that you should not go for USB...