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"Jeff Strickland" <crwlr@yahoo.com> wrote in message
news:2vydnXFi370W0jzYnZ2dnUVZ_r2onZ2d@ez2.net...[color=blue]
>
> "Nicholas Bourne" <nbourne@optusnet.com.au> wrote in message
> news:45a0bc0e@dnews.tpgi.com.au...[color=green][color=darkred]
>>>
>>> I do not agree. The markers should be within a few meters of where they
>>> say they are. My disagreement ias solely your assertion of the rate of
>>> error that the highway department will tolerate. I think that the error
>>> in placing a mile marker is within a few meters, not a hundred meters. A
>>> highway marker will be omitted before it will be placed in the wrong
>>> location.[/color]
>>
>>
>> In the city they maybe but out in the country where I live you sometimes
>> can't be that accurate. Our roads go over very changeable soil types. In
>> the black soil plains the main highway has more waves in it than a
>> rollercoaster. Personally I don't trust them to perfectly accurate with
>> the distance markers over our distances. I think 200Km +- 100m is fine.
>> when the raod is dead straight and you don't see another car for the
>> whole distance I don't really care.
>>[/color]
>
> I don't live in the city either. I do live in California, and your mileage
> may vary, but they will not plant a mile marker before they plant one in
> the wrong place.
>
> The purpose of a mile marker isn't for you to calibrate your odometer or
> speedometer (but they are useful for that), they are for emergency crews
> and highway maintenance crews. When you are on the highway and observe a
> crash, you can tell the emergency operator that you are east of mile
> marker 27.5, and they have a better idea of where to send the response
> crew. Cellphones these days have a GPS-like circuit built in that helps
> the emergency operator find you as you are making the call, so your
> observance of mile markers isn't all that important, but that is why the
> markers are there.
>
> If there is a mile marker planted on the side of the road, you can take it
> to the bank that it is precisely where it says it is, within a few meters.
>[/color]
I found this research paper:
[url]http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_506.pdf[/url] and while I did
not read all 108 pages or some other info on other sites, I found some
surprising information. I would have thought that there is a uniform method
of placing mile markers, but there is not, and methods and accuracy vary by
state.

Among the methods used to measure position are optical survey instruments,
laser distance measuring, measuring wheels, digitized aerial photographs,
and distance measuring devices installed in vehicles (fancy odometers), with
the most common being a combination of several methods.

Some are measured in 2 dimensions and some are measured in 3, taking
elevation into account.

Some measure from a lane centerline, some measure the centerline between
directions, and some measure between markers.

There is relative accuracy (accuracy between markers and geographic
locations) and there is spatial accuracy - distance from a specified
starting point in the road system.

Depending on the state and the method used to place the particular marker,
it looks like accuracy will vary from inches to about 300 feet.

For the purposes of determining odometer and/or speedometer accuracy, the
most accurate method seems to be GPS or measuring the mile marker distance
over as long a distance as possible and averaging out.
--

Ray O
(correct punctuation to reply)