An unachievable goal.
Everyone should have at least one unachievable dream.
If it is your first year in business saying, "I will make $500,000 profit my first month," is most likely unachievable.
Geostatistical prediction will then be used to map C stocks at a previously unachievable resolution for moorland catchments.
My response was that while in truth the standards set forth might be unachievable, they were not unapproachable.