ISS Detector - App Accuracy

Discussion in 'Satellite and Space Communications' started by N7AY, Sep 22, 2021.

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  1. N7AY

    N7AY Premium Subscriber QRZ Page

    I've had "ISS Detector" on my iPhone for some time - very impressive app, well, until now.
    For several days now I have been recording satellite pass info for the following day into a spreadsheet only to find that when the next day comes all the parameters of each pass have changed!

    Is ISS Detector unable to predict pass information a day in advance?! I'm seeing changes in rise and fall times as much at 30 minutes, Max-E changing by as much as 30%, even the order in time the satellites pass is changing. In other words, what I recorded yesterday for 12 passes of 6 different birds is all wrong according to ISS Detector this morning.

    What gives?
     
  2. KS1G

    KS1G Ham Member QRZ Page

    I have not seen those kinds of errors; for example predicting an RS-44 pass for tomorrow afternoon (24 hrs ahead) I get about the same prediction as from SatPC32. I do refresh the predictions just in case when I am getting ready for a pass. I assume that the app uses latest keps when doing that. Sometimes the app will only display ISS passes; hitting referesh fixes that. Not disagreeing you have a problem, I have not duplicated it for myself. Is the difference in times and max elevation comparing what you recorded from ISS Detector the day before vs. what it shows when you are trying to use it?

    Having the app on a phone lets me bring it with me and display the information in real-time. I can use desktop tracking software (SatPC32, GPredict, I assume Mac Doppler (no experience)) or web-based services to produce and print a list of passes and don't need ISS Detector or any phone app.
     
  3. WS9K

    WS9K Ham Member QRZ Page

    VE3TSV likes this.
  4. N7AY

    N7AY Premium Subscriber QRZ Page

    Yes, the differences were between parameters taken from ISS Detector one day and comparing them to what ISS Detector was reporting the next day. It happened to me 3 days in a row. Also, I’m sure ISS Detector was updated when I took the numbers as I was using it at the same time to track birds. It seems to be getting the current day parameters right but can’t get future days right. They are way off too, not just the small changes you’d expect from having old Kep data.

    I’m trying to record these parameter as I’m headed out to a location with no cell service and I don’t trust ISS Detector to work properly for a day or two with no internet connection.

    It would appear that the iPhone version of ISS Detector doesn’t have a “refresh” button, but I’m not convinced the problem is not being updated anyway.
     
  5. N4UFO

    N4UFO Ham Member QRZ Page

    I have an N2YO page bookmarked for about every satellite I work... it has a very good prediction page. I have used it just as you do for 'in advance' predictions. Then for 'on scene' I have a tablet and use AMSATdroid... no realtime cell service needed. Drawback is the satellite list is HUGE and may take a while to find a desired sat. But the display is good to refer to in realtime.
     
  6. KS1G

    KS1G Ham Member QRZ Page

    That has to be frustrating. I'd cross-check the ISS detector provisions against one of the listed on line sites and https://www.amsat.org/track/index.php (you can cut and paste the amsat.org predictions into a spreadsheet if that helps). I've found amsat predictions to be spot on. As far as keps age, a few days to weeks should not be a problem other than for the ISS. I've run Field Day predictions 6-8 weeks ahead and while specifics were off, the general time, direction, and high/low/medium elevations were usable, other than for horizon skimmers (just above or below). On Android, "refresh" is a menu selection from the top right button, next to the down triangle filters button.
     

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