[Taxacom] odometer georeferencing

Frederick W. Schueler bckcdb at istar.ca
Mon Feb 7 12:02:59 CST 2011

On 2/7/2011 12:34 PM, Doug Yanega wrote:

> At any rate, Gunson's proposal would create a very nice and useful
> tool, certainly, but like any tool, one has to be careful to use it
> for the proper job. But Eco-Kare is a commercial enterprise - would
> these data be free, or for sale?

* Kari Gunson is providing GIS support for our 30-years-later expedition 
- http://fragileinheritance.org/projects/thirty/thirtyintro.htm - so 
she's doing the highways we'll need, and if the method succeeds, will 
put them up for download, with the suggestion that if others need 
similar tables for other routes, the making of these would be a 
commercial transaction. She's already used this method for locating 
roadkills along highways for her own research in Banff National Park.

In the present case, all our mile/kilometrages are odometer readings, 
and the reference locations are central bridges or intersections of 
settlements, or intersections or bridges over streams away from 
settlements. I tend not to use settlements of substantial size as 
reference locations because of the ambiguity of central reference 
points. Distance markers along highways tend to be absent or cryptic in 
Canada, and I've never heard of them being used for specimen/observation 
referencing, except along northern logging roads far from settlements.

> Fred Schueler wrote:
>> Like many who antedate 1995, I've got a huge body of observations
>> "georeferenced" by odometer readings along highways.
>> Kari Gunson - http://www.eco-kare.com/ - has proposed to GIS these by
>> listing the geographic co-ordinates of every 10m of the highways they're
>> along, so I'll just be able to select reference points from web maps,
>> calculate the distance from the reference points, and then assign the
>> observation the co-ordinates that match these distances.
>> I wonder if this method has been used by others, and if there's any
>> place where such tables are archived? I haven't tried to search for such
>> accounts on line, since I don't know what the method would be called.
> As someone who has a full-time technician hired just to do
> georeferencing, I had not heard of any such attempts at mapping
> "reference points" along highways, but it sounds very promising -
> right now, this sort of procedure is done manually with Google
> Earth's path-tracing tool. That being said, one observation MUST be
> kept in mind:
> There is a difference between specimen labels that refer to highway
> markers versus labels that refer to odometer readings.
> A label based on highway markers *should*, in principle, explicitly
> state "marker #" somewhere, and if it does not, then making the
> assumption that the label refers to a marker can lead to error, given
> that mile/kilometer numbers don't necessarily start at the edge of a
> town (which is where most people will zero their odometer reading).
> Accordingly, there can be up to a several-mile discrepancy between
> the two methods; we have enough cases of known localities with
> various collectors' mileage readings to be quite confident that one
> *cannot* start measuring distance from the center of a town when
> georeferencing. At this point, for cases without highway markers,
> there really is no good substitute for a human being visualizing
> where he/she would zero the odometer, using a Google Earth satellite
> photo. Even the best automated lookup tools (i.e., those with error
> radius, like Biogeomancer) are frequently *woefully* far off simply
> because they use the center of a town as the starting point (e.g.,
> just imagine what happens with automated lookup of a specimen from "1
> mi E" of a city that is 5 miles in radius).
> Highway markers should also, in theory, be quite stable once
> georeferenced, where the edge of a town is a subjective quantity, and
> subject to *wide* interpretation - especially when dealing with
> legacy material 50 or more years old. At least for US material, our
> experience is that the vast majority of labels use odometer readings,
> and thus are more subject to error. I have little doubt that this is
> correlated with the inconsistency across the US in the presence and
> visibility of highway markers.
> It would definitely be interesting if there were variations between
> countries in how highway markers were numbered (e.g., if any of them
> started from the edge of a town/city, and what happens if that edge
> shifts over time).
> At any rate, Gunson's proposal would create a very nice and useful
> tool, certainly, but like any tool, one has to be careful to use it
> for the proper job. But Eco-Kare is a commercial enterprise - would
> these data be free, or for sale?
> Sincerely,


fred schueler
          Frederick W. Schueler & Aleta Karstad
Bishops Mills Natural History Centre - http://pinicola.ca/bmnhc.htm
now in the field on the Thirty Years Later Expedition -
Daily Paintings - http://karstaddailypaintings.blogspot.com/
     RR#2 Bishops Mills, Ontario, Canada K0G 1T0
   on the Smiths Falls Limestone Plain 44* 52'N 75* 42'W
    (613)258-3107 <bckcdb at istar.ca> http://pinicola.ca/

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