**What is the Spatial Reference system?**

All the data layers use:

USA_Contiguous_Albers_Equal_Area_Conic_USGS_version WKID: 102039 Authority: ESRI Projection: Albers False_Easting: 0.0 False_Northing: 0.0 central_meridian: -96.0 Standard_Parallel_1: 29.5 Standard_Parallel_2: 45.5 latitude_of_origin: 23.0 Linear Unit: Meter (1.0) Geographic Coordinate System: GCS_North_American_1983 Angular Unit: Degree (0.0174532925199433) Prime Meridian: Greenwich (0.0) Datum: D_North_American_1983 Spheroid: GRS_1980 Semimajor Axis: 6378137.0 Semiminor Axis: 6356752.314140356 Inverse Flattening: 298.257222101

**Why isn't my data projected?**

All the data is projected using USA_Contiguous_Albers_Equal_Area_Conic_USGS (described above in What is the Spatial Reference system). ArcGIS users below version 10.0 have reported some data not projected or undefined. Please try to "define the projection system" using the details in Spatial Reference system and ArcGIS tool set.

**Why aren't all the coordinate systems identical?**

All the data has been projected (this is not the same as coordinate system) using USA_Contiguous_Albers_Equal_Area_Conic_USGS (described above in What is the Spatial Reference system). We have observed that as we maintain our cyberinfrastructure, sometimes the coordinate system will vary depending on your HUC-12 choice, hence spatial location. ArcGIS will choice the appropriate conversion automatically, based on preserving area. However, we highly recommend that the user convert all data to a projection and coordinate system best suited to their project needs/purposes.

**Can you recommend any free projection tools?**

We recommend GDAL. Link to GDAL Tutorial