The StreetMap extension data is unprojected, in a spherical, geographic coordinate system in decimal degrees (DD). The data came from GDT's Dynamap 1000 product. Since Dynamap 1000 version 1.0 was based on TIGER 92, the datum is the North American Datum of 1927 (NAD 27). The positional accuracy of all features in the dataset is +/- 3 feet.
The StreetMap 2000 extension data is also unprojected, decimal degrees, geographic coordinates system, and NAD 83 datum. The compressed street data layer was generated based on Geographic Data Technology's Dynamap 2000 product, version 9, 1999. The data is more current and contains more features and attributes.