[Nhcoll-l] Google Earth fix?

[Douglas Yanega]

On 1/11/22 1:10 PM, Cassidy, Kelly Michela wrote:
>
> Ha ha, that’s the type of location description that makes me want to 
> throw random (virtual) darts at a map, because it would probably be as 
> accurate as the description. I don’t think you have a GeoLocate or 
> Google Earth problem; you have a collector who was probably either 
> guessing how many road miles he’d traveled or guessing at which county 
> he was in.  All you can do is decide whether you want to put the point 
> 17 miles out in a different county or put it in the right county, but 
> less than 17 miles down the road. Either way, the “Uncertainty” field 
> gets a big number.
>
Quite the opposite.

This collector was scrupulous in reading his trip odometer, and 
scrupulous about resetting the trip odometer whenever he left a town. 
Carrizozo is a town less than a mile from end to end. I assume that the 
resulting georeference is accurate to within a mile, accordingly (a half 
a mile error for the odometer, and at most a half a mile for the edge of 
the town).

The uncertainty radius on most such labels is typically databased as 2 
km, sometimes much less (e.g., "vic. Big Dune, 4.3 mi W jct Hwy 95 & 
373" is accurate to within a few hundred meters). Many landmark features 
are small, and stable over very long time frames, if they are not 
associated with large sprawling urban areas. A label saying 17 mi W 
Carrizozo is *very* precise; a label saying 17 mi W Albuquerque is 
nearly useless. Entomologists in pre-GPS days (but after 1930 or so) 
often reported their odometer readings to the nearest 1/10 mile, and/or 
also gave elevation from altimeter readings. It is not at all a 
difficult thing to recreate a person's trip when you know that the way 
entomologists collect is to drive around, stop the car at the side of 
the road, collect nearby, and then get back in the car and go on to 
another stop. It's a *very* rare thing for a collecting locality to be 
somewhere from which one's parked car would not be visible. In fact, the 
error radius associated with how far a person might have wandered on 
foot from their parked car is probably nearly the same as the error 
associated with determining where they had to have been parked.

Also, in those few circumstances where we DO have additional evidence to 
use as a check (field notes, records from more than one collector at the 
same site, direct questioning of collectors, etc.), the precision and 
accuracy of post-facto georeferencing *along roads* has proven to be 
pretty solid on the whole; I can't think of a single such case where the 
actual spot was not inside the error radius we'd assigned. That being 
said, labels made prior to the routine use of odometers are generally 
hopeless, as are labels that only give the names of cities or towns, or 
irregular or linear features like a lake, river, mountain, or canyon. 
THOSE records usually have a very large associated error radius. 
Conversely, there are a fair number of collectors who write down 
incorrect GPS values on their labels, or mis-transcribe things so you 
get nonsense entries like "33° 78.56" N", so even the access to 
technology doesn't prevent careless mistakes that require careful 
georeferencing.

Peace,

-- 
Doug Yanega      Dept. of Entomology       Entomology Research Museum
Univ. of California, Riverside, CA 92521-0314     skype: dyanega
phone: (951) 827-4315 (disclaimer: opinions are mine, not UCR's)
              https://faculty.ucr.edu/~heraty/yanega.html
   "There are some enterprises in which a careful disorderliness
         is the true method" - Herman Melville, Moby Dick, Chap. 82
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