low power rfid on objects to aid in mapping
Not directly.

For any sort of range you need to be using 900MHz RFID so I'm going to assume that from here on.

All that the RFID system can tell you is the data encoded on the tag, the frequency used to communicate (the system frequency hops) and the RSSI (received signal strength indicator). That isn't enough to tell where a tag is.

If signal strength was purely a function of distance then with 3 measurements from 3 different locations it would be possible to calculate a tag location. 

Unfortunately in the real world signal strength is a function of separation distance, RFID antenna height and tag height above the ground, the frequency used (height and frequency impact the strength of the ground bounce signal) and the types and orientations of the two antennas. Plus a fair amount of random noise.

If you model all of these effects correctly then for a given set of readings you can create a probability map of where within the field a tag probably is.

In a previous role I had worked on a system that given a set of 20 RFID reads, each from a different known location along a straight line at the edge of the field could calculate the location of a tag in a 20m x 20m field to within about 30cm most of the time.