Flappie Posted March 19, 2021 Posted March 19, 2021 (edited) I've been testing the SPA/SKU type II fix procedure with the Caucasus map. I'm getting odd results: Calculated angle is systematically wrong by ~15°. Calculated speed is often incorrect as well. I waited up to 5 minutes between two fixes to be sure the measurement would be effective, but it's not. Angle is 270°, speed is 9.71922 knots. Calculated angle is 254, calculated speed is 14 knots. Edited March 19, 2021 by Flappie solved ---
Flappie Posted March 19, 2021 Author Posted March 19, 2021 Another try with a track attached. This time I got 265° (instead of 270) and 11 knots (good speed estimation). This is much more precise but I don't know what I did differently. How long do you guys wait between two fixes to get a correct course/speed calculation? AJS37_SKU.trk ---
JG300_Papaye Posted March 19, 2021 Posted March 19, 2021 This depend of your fix. Do you perform a visual or a radar fix? [sIGPIC][/sIGPIC]
JG300_Papaye Posted March 19, 2021 Posted March 19, 2021 (edited) Radar fix precision depend of your scale, try with different scales. A pixel doesn't have the same wide in 15km scale and in 120km scale. On the second screen the ship is not in the center of the circle, maybe a bad fix. And try with the vertical fix. Edited March 19, 2021 by JG300_Papaye 1 [sIGPIC][/sIGPIC]
Flappie Posted March 19, 2021 Author Posted March 19, 2021 I agree, but I didn't think I would get such a huge error margin (15° difference). I'll do the maths with coordinates to better understand what happens. 1 ---
Flappie Posted March 19, 2021 Author Posted March 19, 2021 Merci @JG300_Papaye! I did a radar fix with range 120 and saw my target fix coordinates were quite a bit up north the real position, meaning the measured course would obvisously be incorrect. Then I did the same SKU measurement only with visual fixes this time: this allowed me to see target measurement works just fine (271°-10 knots, whch grossly corresponds to 270-20km/h). False alarm. ---
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