Re: Accurate Lat/Long Info

From: Ralph McConahy (
Date: Wed Jun 07 2000 - 21:58:55 PDT

  • Next message: John Breckenridge: "WOW and Thank..."

    >>This site has recently added aerial photos for the full U.S.
    >Actually, not, so far as I can tell.
    True. I noticed that the day after I posted the above false statement. The
    reason for my assumption was that the U.S. index map used to have a number
    of "white spaces" on it indicating no map available (including the town
    where I live). The other day, I noticed that now has
    an aerial photo of where I live, and I was pleasantly surprised to see that
    on the U.S. index the whole map is green. What I later found out, however,
    is that one shade of green equals "USGS Topographic Map" only instead of a
    photo. Thanks for pointing out that "100% of the conterminous United States
    is expected to be completed by the end of 2001."
    >>After zooming in on your observation location, click "Image
    >>Information" on the left for a Lat/Long grid.  You should be able to
    >>interpolate to within 0.0001 degrees.
    I was just on the site and noticed that they have
    redesigned it. The commands are now just words at the top instead of buttons
    to the left. "Image Information" is now "Image Info" and the three words
    "Relief" (not much good for sat viewers), "Topo", and "Image" appear in a
    group. Presently, I couldn't get it to call up topo maps for any location
    (seems like that particular database is unavailable).
    Instead of clicking on the big map a number of times in order to zoom in on
    a city, it is quicker to just type a city into the Find box and click GO. A
    list of available photos and maps will appear for selection.
    >I'm guessing that those of us who carry around 4 decimal places
    >may be carrying around a little hubris as well.
    I've made attempts to zero in on my observing location and have seen three
    different computer programs that show a delta of +/- 0.0001 between the
    three in Lat and zero to +0.0001 in Long. The grid lines on the photo agrees in the same range as these. A borrowed
    GPS receiver averaged +/- 0.0002 from the map programs. I agree that to
    0.0001 degrees is pushing it, but it seems that with a little work we can
    have confidence within 0.0002 degrees (or about +/- 22 meters in latitude,
    and about +/- 22*COS(Lat) in Longitude).
      Ralph McConahy
      34.8830N  117.0064W  (+/- a couple ten-thousands)  675m (+/- at least 5m)
    Unsubscribe from SeeSat-L by sending a message with 'unsubscribe'
    in the SUBJECT to

    This archive was generated by hypermail 2b29 : Wed Jun 07 2000 - 21:59:23 PDT