Thanks Brian,
This is a fearsomely technical topic indeed and I don't know enough to be sure of the likely error with historic lat/longs taken with sextant combined with dead reckoning long ago. Old shipboard locations are likely to be only to the nearest minute of a degree, which may be plus or minus about 700m, then add error for the equipment used on to that. But the lat/long for Challenger station 167A still sits almost plumb in the centre of Queen Charlotte Sound entrance, New Zealand just where they said it was taken in 1874. Nice, whether by luck or skill.
Moving forward to positions taken decades ago rather than in the 1870's - Given that beaches advance or retreat naturally it's likely to be that softshore intertidal locations will be out of kilter with current beach positions with time. For instance I have a beach type locality designated by me that is now filled in by human 'improvement'. Not too worried by that. It's still where I collected the animal.
What I was aiming at were current lat/long figures (presented in current papers) that should be checked online in Google maps to see if the person who supplied the data has made a silly mistake that is pointing literally many miles/kilometres from where the location was. Not a 100m out due to a different datum (though this is perhaps unlikely given the universality of WGS84) but 1000's of metres out. We all make silly mistakes, I make them every day, and checking to see that one has NOT done so in a paper intended for permanent record is the least one can do.
Geoff
-----Original Message-----
From: annelida-bounces from oat.bio.indiana.edu [mailto:annelida-bounces from oat.bio.indiana.edu] On Behalf Of Brian Paavo
Sent: Tuesday, 8 October 2013 2:34 p.m.
To: annelida from magpie.bio.indiana.edu
Subject: [Annelida] geographic points
Thanks Geoff for that link to a handy tool. I spend some time
developing geographic database structures and encouraging students and
professionals to manage biological information in proper object-oriented
databases. I have found several problems similar to what you describe
resulting from an underappreciation of:
1) The variety of cartographic datums (what strange word! A cartographic
datum is the single reference point, but there are many of them!)
2) Original collectors and curators dismissing the importance of
including metadata fields on labels and in data systems.
So I encourage worm folk everywhere to become a little more
geographically savvy! The WGS84 system we typically assume now when no
meta-data are provided didn't come into common use among non-GIS folks
until the 1990s and very few specimen tags record what coordinate system
was used. While it does not include all of the many hundreds of spatial
reference systems in existence, the EPSG registry
(http://www.epsg-registry.org/) will provide folks with some likely
alternatives if a type locality is nonsensical and they'd like to
compile a list of alternative candidates. Of course, we have little hope
of properly locating historical records which are still wrong, but
plausible.
Cheers,
Brian
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Brian Paavo, PhD
Benthic Science Limited
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Westwood, Dunedin
New Zealand 9035
http://www.benthicscience.com/
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