This post has to do with using coordinates to try to predict where to best observe iridium flares. I am now teaching 8th grade science as well as all high school science and have astronomy and satellites as part of the curriculum in 8th grade science. I introduced the young students to Heavens-Above and am trying to set up a way that I can quickly predict a coordinate to go to using a GPS unit to see -8 flares. A few of the students are now hooked ion using GPS technology too. Tonight I wanted to see what longitude (with two latitudes) I needed to add into my GPSr as a one-legged route so that I could, anywhere along that line, see a -8 iridium flare. It was only some 6.8 km E of my computer desk. [I get a reading on my GPSr in the upper room of my house even though it's indoors, I discovered.] Other than going to H-A I went to a website that I often go to get an idea as to how much of a degree so many Km would be and vice versa. However, I seemed to have had some trouble. As a result I began to simply move the longitude eastward on H-A while checking the same flare till I got a point with a -8 flare. However, I would rather be able to make a conversion from km to fractions of a degree for my latitude so I could see what H-A says and make a quick adjustment to a particular longitude and take off using my GPS as a guide. The thing that is puzzling me now is that the website http://jan.ucc.nau.edu/~cvm/latlongdist.html where I customarily get my distances between two points seems to be giving me some lousy data in one instance at least. I was suing that website to try to get some data about how many km are in a certain amount of longitude at my latitude. I found that when I plug in two coordinates in decimal degrees, varying only the longitude, I get an answer that seems wrong then when I type in the exact equivalent in degrees, minutes & seconds for the two points I get quite a different result. The degrees minutes seconds mode at the above website got me a value that was the same as what I got here: http://www.fcc.gov/mb/audio/bickel/distance.html when using the same two coordinates. Here is what I got at the first website (the edu/ one) when I plugged in the decimal values given here: Distance between 42.473567'N 92.360250'W and 42.473567'N 92.526917'W is 0.3092 km. Here is what I got at the SAME website when I typed in the given DMS values: Distance between 42 28' 25"N 92 21' 37"W and 42 28' 25"N 92 31' 37"W is13.6844 km.See the difference?This is what I got at the second website (the gov/ one) with the DMS values shown: Distance between N Latitude 42 28 25.00, W Longitude 92 21 37.00 (Point 1)and N Latitude 42 28 25.00, W Longitude 92 31 37.00 (Point 2) is 13.668 kilometersNow that's close to the DMS value from the other one. Can someone tell me of a website that I can go to in which I can use decimal degrees, like H-A uses, to get reliable distances per degree etc? Thanks! Tom Iowa USA ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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