Indexes are guides to zone based layers. Find out your UTM zone, time zone and more.

Hydrological Units
Clickable image map indexing the USGS hydrological units. The USGS has divided the nation up into 21 regional hydrological units. You can also download data from this site.

State Plane Datum Shifts
Detailed descriptions of all of the NAD83 zone definitions and how they relate to older NAD27 zones. A small shaded map is also shown as well as UTM zones are appended to the descriptions.

USGS Index Maps
From the GIS Data Depot site. Search for USGS Quadrangles by state.

UTM Grid Zones
Map of the world overlayed with UTM grids. Find out the UTM grid your area is located in.