+RaynPengi Posted August 25, 2022 Share Posted August 25, 2022 Like many I use the Geocaching Toolbox to help solve coordinate issues. However it was pointed out to me that the intersection of lines calculation gives a different answer to Cachesleuth. I contacted Cachesleuth who looked at it and claimed theirs was the more accurate. If you look at the Toolbox map the intersection pointer is not always right at the intersection. I then found a third website Geo.Javawa.nl which agreed with Cacheslueth. So what to do now? 1 Quote Link to comment
RuideAlmeida Posted August 25, 2022 Share Posted August 25, 2022 9 minutes ago, RaynPengi said: So what to do now? Did you asked on their website already? Quote Link to comment
+fizzymagic Posted August 26, 2022 Share Posted August 26, 2022 3 hours ago, RaynPengi said: Like many I use the Geocaching Toolbox to help solve coordinate issues. However it was pointed out to me that the intersection of lines calculation gives a different answer to Cachesleuth. I contacted Cachesleuth who looked at it and claimed theirs was the more accurate. If you look at the Toolbox map the intersection pointer is not always right at the intersection. I then found a third website Geo.Javawa.nl which agreed with Cacheslueth. So what to do now? How much did they differ? Since there is a quick-and-dirty method that uses a spherical approximation, I expect that one of the sites is using that. If so, then that site is wrong. If you send me an example of the results I will be able to tell you which is correct, as I have written my own. 1 1 1 Quote Link to comment
+fizzymagic Posted August 26, 2022 Share Posted August 26, 2022 Well, I tested the two sites and I can confidently say that Geocaching Toolbox is incorrect. By a surprising amount. The Dutch site agrees exactly with my calculations. Interestingly, the Geocaching Toolbox result is not the spherical-Earth approximation. It is just wrong. Data Line 1: N 37 50.000 W 122 00.000 - N 37 00.000 W 121 00.000 Line 2: N 37 00.000 W 122 00.000 - N 37 50.000 W 121 00.000 High-accuracy Intersection = N 37 25.203 W 121 30.000 (37.42004708, -121.50000000) Residual = 2.85e-24 it=68 From N 37 50.000 W 122 00.000: Fwd = 316.255086 Rev = 135.949825 From N 37 00.000 W 122 00.000: Fwd = 223.744914 Rev = 43.442542 Spherical Intersection = N 37 25.203 W 121 30.127 (37.42005687, -121.50211660) Residual = 1.79e-23 it=68 From N 37 50.000 W 122 00.000: Fwd = 316.375194 Rev = 136.071226 From N 37 00.000 W 122 00.000: Fwd = 223.622234 Rev = 43.321141 Geocaching Toolbox answer: N37° 25.307' W121° 30.000' (off by almost 200 m!) 1 1 4 Quote Link to comment
+Hügh Posted August 26, 2022 Share Posted August 26, 2022 5 minutes ago, fizzymagic said: It is just wrong. Is Geocaching Toolbox by any chance doing a naive 2d Cartesian intersection? Quote Link to comment
+RaynPengi Posted August 27, 2022 Author Share Posted August 27, 2022 Thanks for that. I checked the two point intersection and that seems to be ok on distance and coords but gives a different bearing? What I do now is "assume" people are using toolbox to get the right answer but allow the Cachesleuth one in Geocheck as well. For new ones I will use Cachesleuth but put in a warning, though that does give the game away.. Quote Link to comment
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