An "ESRI Shapefile" is composed of several individual files which correspond to each other. We currently export a Shapefile with:

• .shp - required geometry features
• .shx - required feature indexes
• .dbf - required feature attributes in dBASE database format
• .ovf - optional OGR virtual layer

When loading a Shapefile into QGIS or ArcView, the application doesn't know what CRS to use, forcing the user to manually choose, or - worse - defaulting to the project CRS, which may not be correct.

We should additionally write a .prj projection file, which contains the CRS in Well-Known Text format.

For EPSG:4326 (WGS84 lat lon), its contents will be something like:

GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.257223563,
            AUTHORITY["EPSG","7030"]],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0,
        AUTHORITY["EPSG","8901"]],
    UNIT["degree",0.0174532925199433,
        AUTHORITY["EPSG","9122"]],
    AUTHORITY["EPSG","4326"]]

...or:

GEOGCS["GCS_WGS_1984",
    DATUM["D_WGS_1984",
        SPHEROID["WGS_1984",6378137.0,298.257223563]],
    PRIMEM["Greenwich",0.0],
    UNIT["Degree",0.0174532925199433]]

...but we'll need to test to make sure the format is compatible with both QGIS and the OGC world, as well as ESRI's ArcMap (since ESRI used/uses their own bastardized WKT format).