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I remembered where it was!

On Oct 31, 2006, at 3:23 PM, Alexandre E Eremenko wrote:

>
>
> Fred,
> Thanks a lot.
> How did you find my appartment,
> by the address or by co-ordinates?
> :-)
>
> Alex.
>
> On Tue, 31 Oct 2006, Fred Hebard wrote:
>
>>
>>
>> Alex,
>>
>> It's full featured.  There's a search box, and you can change the
>> size and zoom of the map, and look at maps of different scale.  It
>> starts out with the 7.5' series maps.  The captions are cut off, but
>> the contours have elevation in feet above sea level marked here and
>> there, always on the darker lines, and you can count the divisions
>> between.  Your apartment in West Lafayette has the 670 contour
>> running through the middle.  The fine contours there are at 10 foot
>> intervals.
>>
>> Fred
>>
>> On Oct 31, 2006, at 12:51 PM, Alexandre E Eremenko wrote:
>>
>>>
>>>
>>> Thanks, Fred.
>>> This seems to be a demo with limited features,
>>> and I am not sure where on the map elevation
>>> is shown, and in which units.
>>> Can you give an example?
>>>
>>> Alex
>>>
>>> On Tue, 31 Oct 2006, Fred Hebard wrote:
>>>
>>>>
>>>>
>>>> Alex,
>>>>
>>>> The website, http://www.topozone.com/ has topographic maps covering
>>>> the U.S., from which you can extract your elevation to the
>>>> nearest 20
>>>> feet or so, which is close enough.
>>>>
>>>> Fred
>>>>
>>>> On Oct 31, 2006, at 10:33 AM, Alexandre E Eremenko wrote:
>>>>
>>>>>
>>>>>
>>>>> Jean-Philippe,
>>>>> Thanks.
>>>>> I have no problems with conversion of units,
>>>>> (though it is sometimes annoying with pressure
>>>>> for which at least 5 different units are commonly used:
>>>>> psi(=punds/square inch), millibar(=1000 dynes/square centimeter),
>>>>> Pascal (not to be confused with psi:-),
>>>>> inches of mercury and
>>>>> millimeters of mercury.
>>>>> And I almost forgot the sixth unit: the atmosphere:-)
>>>>>
>>>>> Most barometers on e-bay use one or two of these units,
>>>>> so one has to hand a conversion table besides the barometer:-)
>>>>>
>>>>> Is there a convenient source on the web to find one's altitude
>>>>> over the sea level, (I mean for those unfortunate ones
>>>>> who do not live on a sea shore)?
>>>>>
>>>>> Alex.
>>>>>
>>>>> On Tue, 31 Oct 2006, jean-philippe planas wrote:
>>>>>
>>>>>> If you know the elevation of your observation spot as well as the
>>>>>> atmospheric pressure reduced to sea level (QNH for the pilots)
>>>>>> you
>>>>>> can determine the local pressure (QFE for the pilots) knowing the
>>>>>> fact that every 28 ft of altitude the pressure decreases by 1
>>>>>> millibar in the lower standard atmosphere . I'll look for the
>>>>>> formula in inches of mercury if its the way the weather channel
>>>>>> provides this info.
>>>>>>   JPP
>>>>>>
>>>>>> Fred Hebard  wrote:
>>>>>>
>>>>>> That's correct! I started looking into this, but gave up.
>>>>>> Hopefully, the physicists will jump in here.
>>>>>>
>>>>>> On Oct 31, 2006, at 8:59 AM, Alexandre E Eremenko wrote:
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Fred,
>>>>>>> I see, this sounds reasonable.
>>>>>>> But then I need a barometer, or to correct
>>>>>>> the pressure from the Weather channel for
>>>>>>> my altitude, because,
>>>>>>> if I understand correctly, the pressure broadcast
>>>>>>> for the weather prediction is reduced to the sea level.
>>>>>>>
>>>>>>> Alex
>>>>>>>
>>>>>>> On Tue, 31 Oct 2006, Fred Hebard wrote:
>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> Alex,
>>>>>>>>
>>>>>>>> Use the actual pressure. That is the determinant for the
>>>>>>>> refraction
>>>>>>>> correction. The elevation above sea level has an insignificant
>>>>>>>> effect on parallax, when you consider that the radius of the
>>>>>>>> earth is
>>>>>>>> about 3400 nautical miles, but significantly reduces
>>>>>>>> refraction via
>>>>>>>> the effect on barometric pressure.
>>>>>>>>
>>>>>>>> Fred
>>>>>>>>
>>>>>>>> On Oct 31, 2006, at 8:27 AM, Alexandre E Eremenko wrote:
>>>>>>>>
>>>>>>>>> Related question: the barometric pressure in the refraction
>>>>>>>>> formula.
>>>>>>>>> Should I use the actual pressure at my observation site,
>>>>>>>>> or should I "reduce it to the sea level"?
>>>>>>>>> The actual pressure at my site reflects not only the deviation
>>>>>>>>> from the standard atmosphere but also my altitude over the sea
>>>>>>>>> level.
>>>>>>>>>
>>>>>>>>> Alex
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> JPP
>>>>>>
>>>>>> ---------------------------------
>>>>>> Get your email and see which of your friends are online -
>>>>>> Right on
>>>>>> the  new Yahoo.com
>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>>>>
>>>>
>>>>
>>>>>
>>>
>>>
>>>>
>>
>>
>>>
>
>
> >


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