With the Laserfiche.RepositoryAccess assembly, use Entry.GetGeographyData to retrieve and Entry.SetGeographyData to set it. Entry.GetGeographyData returns an EntryGeography object and you can use the Laserfiche.RepositoryAccess.Spatial.GeoConverter class to decode the coordinates:

EntryGeography geoData = Entry.GetGeographyData(entryId, session);
if (geoData != null && geoData.GeoObject != null && geoData.GeoObject.Length > 0)
{
    // EntryGeography.GeoObject uses the WKB format (https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry)
    var index = 4; // Skip WKB header and start on the geometry type byte
    var decoded = GeoConverter.DecodeWkb(geoData.GeoObject, ref index);
    if (decoded is Point2D)
    {
        Point2D point = (Point2D)decoded;
        double latitude = point.P.Y;
        double longitude = point.P.X;
    }
}