Catching lat lon in wrong country errors

John Irish jirish at MWEB.COM.NA
Fri Jan 7 07:41:12 CST 2005

Doug Yanega wrote:

 > I would have thought the idea
 > was to use an automated procedure only *after* a human has done the
 > georeferencing, in an attempt to catch any errors the *human* may
 > have made.

This is what I thought, too.

Scenario: human inputs locality data into database. Assume this includes
both coordinates (from whatever source) and some indication of the
administrative unit the locality is situated in (whether country,
province, district or whatever). While the human can read a map and
type, he/she regularly misreads or mistypes. The program checks whether
the given coordinates are actually within the borders of that country
(or other unit) and alerts the human if it is not. The mistake can be
rectified immediately - in fact, grossly wrong data never even enters
the database.

This is not automated georeferencing, rather, automated (partial)
verification of the results of human georeferencing. Partial because it
isn't foolproof - wrong coordinates in the right country will not be
flagged as errors. You can improve machine accuracy by using polygons
instead of bounding boxes, as I suggested, and by using smaller polygons
(e.g. districts instead of provinces).

 > In essence, I'm curious as to whether my impression - that it sounds
 > like people are talking as if the idea is to have the programs doing
 > the primary georeferencing, and humans doing the error-checking,
 > rather than the other way around - is because I'm not understanding
 > what people are saying, or because they actually *believe* that's the
 > proper approach?

Nope, not me.

Dr. John Irish
Tel./Fax +264-61-202-2038; Cell/SMS: +264-81-269-6602
P.O. Box 21148, Windhoek
Namibia Biosystematics Web Portal:

"The universe is full of magical things patiently waiting for our wits
to grow sharper - E. Phillpots"

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