Pelican Pete just finished explaining a simple exercise with NavPak Android/Kindle to get some meaningful numbers on the screen, and a couple of plots to boot.” So I responded “Sorry Pete, I started daydreaming and missed it all, can you give me another example in different words this time?” “I would be happy to, if you promise to pay attention.”, Pete replied. We can produce, solve and plot an example sight by just entering one whole number and a few taps here and there. We will use the Almanac function in NavPak to compute an Altitude and Azimuth, which we can use as a hypothetical sight to solve and plot. The first time you start NavPak out-of-the-box, the Assumed Position (AP) and the Destination Position (DEST) will probably be 0,0. You can confirm this by looking at the Globe View where you will see an AP flag and a DEST flag at latitude 0, longitude 0. This is a valid Assumed Position (AP), or you can estimate your own AP using the Ocean Maps. Within 1 or 2 degrees is close enough. As long as we use the same AP to make up the hypothetical sight as we use to solve and plot it, then it should result in a reasonably small Intercept. Start from the Main Menu by going to the GMT Time panel and tap the button: [Set to Clock], then tap [SAVE] to return to the Main Menu. Each sight is going to have a different time. The only way you could have 2 sights at the same time is if you had 2 shooters. From the Main Menu go to the Almanac panel. In this panel, tap the button: [Calc]. This calculates all the planetary positions based on the GMT you saved in the previous step. Use the up and down arrow keys in the Almanac panel to see the Almanac list. Notice that when you scroll through the list, the Altitude (Alt) will be blue or yellow. Blue (-) is below the horizon, and yellow (+) is above the horizon. For our example, scroll till you get to a body with a yellow Alt. Make a note of the nearest whole degree of Alt. We then use this as an example Hs that we can enter into the Sight Reduction panel. Tap the button: [SR ->]. This takes us to the Sight Reduction panel. All the info from the Almanac panel is transferred here to the Sight Reduction panel. All you have to do is enter your Hs here. Since we are using whole degrees to simplify the example, enter the Hs then tap: [HS Deg]. Tap the button: [Calc]. The resulting Intercept (Int') should be less than 30 miles if you used reasonable care estimating the Alt and entering the Hs. In actual practice, whole degrees of Hs is not close enough, so you would also enter the Hs minutes, before you tap [Calc]. Now tap the [SAVE] button to save the sight, and then tap the [Plot] button and you should see a Line of Position (LOP) on the Plotting Sheet. -------------------------------------------------------------------------- In summary:
Go to the GMT Time panel and tap the button: [Set to Clock], then tap [SAVE] .
Go to the Almanac panel and tap the button: [Calc].
Use the up and down arrow keys to select a body with a yellow Alt (+ is above horizon). Make a note of the Alt (whole degrees is OK for the example) . We use the Alt in the Sight Reduction panel as the Hs.
Go to the Sight Reduction panel and enter the Hs then tap: [HS Deg].
Tap the button: [Calc]. The resulting Azimuth (Az) and Intercept (Int') will be shown.
Tap the [SAVE] button to save the sight, and then tap the [Plot] button
and you should see a Line of Position (LOP) on the Plotting Sheet. To be continued...