latitude and longitude designation and collection data

Margaret Thayer thayer at FMPPR.FMNH.ORG
Mon Oct 2 12:11:05 CDT 1995

>Not that the idea [Doug Yanega's suggestion of software to allow tracing
distances on a very detailed map to calculate coordinates] isn't a
>good one, but the barriers are more than just getting the right equipment
>and software.

I agree.  Even worse, *any* kind of reconstruction from existing descriptive
data assumes that different collectors mean the same thing when they say
"10mi NW Placename" on their labels.  Some people mean they measured 10
miles on their odometer as they drove along the <straight | curved |
winding> road between Placename and the collecting site, others that they
found their collecting site on a map (of unspecified scale, detail, or
accuracy) and measured on the map the straight-line (or maybe the estimated
road) distance to Placename.  And of course, "10 mi" from the odometer may
have been either 10.0mi or somewhere within the range 9.6-10.4mi and NW may
reflect the direction the road takes on leaving town or the actual direction
from the town to the collecting site.

Even apparently precise data can be misleading.  When there are no explicit
distances in label data, one still can't be sure what the collector meant -
e.g., that water beetle labeled "Placename" probably came not from the
center of town (where there are no streams or ponds), but from one of the
several bodies of water half a mile to several miles outside town, perhaps
in various directions!  Many collectors have simply used the name of
whatever place on their roadmap was nearest the site and not bothered to add
"messy details" to refine it.   I think we have to accept that there are a
lot of imprecise data around that can't really be corrected after the fact
(if the collector is no longer available or has no additional information).

All these variables make it risky to do anything like detailed GIS with
incompletely documented localities, but as has been said, those localities
may be close enough to be perfectly useful for regional-scale mapping.

I certainly second suggestions that site coordinates obtained by GPS (or
other means if necessary) should be included routinely as part of the data
accompanying all new collections.

Margaret K. Thayer      thayer at
Adjunct Assistant Curator
Field Museum of Natural History - Zoology, Insects
Roosevelt Road @ Lake Shore Drive
Chicago IL 60605, USA   tel. 312-922-9410, ext. 838   fax 312-663-5397

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