Geoff Posted November 7, 2007 Share Posted November 7, 2007 I recently purchased from my local tackle store a map of Botany Bay / Pt Hacking. The map includes a list of GPS marks. To try & get an idea of where these spots are generally located I went into Google Earth to "pin" the spots. This is where it became confusing & perhaps someone can clarify the differences in data. As an example, The map lists a spot called Bate Bay Patches , 34.03.600S 151.11.100E When I go into Google Earth they have extra digits after the 03 , eg 34.03'59.60 The difference that occurs on Google 34.03'00.60 is just S/E of Merries Reef where as 34.03'59.60 is in the middle of Bate Bay. Hope someone can clarify or advise which one to use , 34.03'00.60 or 34.03'59.60 Tks Geoff Link to comment Share on other sites More sharing options...
netic Posted November 7, 2007 Share Posted November 7, 2007 (edited) Google earth operates on Degrees minutes seconds as a standard setting, this setting can be changed on a paid version of google earth but not a free version. The marks you have on your map are in Degrees Decimal minutes, which is the standard form used in australia send me the points and i will convert them for you Edited November 7, 2007 by netic Link to comment Share on other sites More sharing options...
Geoff Posted November 7, 2007 Author Share Posted November 7, 2007 Netic Tks for your response. I have a paid version of G.E. all be it the base price of US$20.00 PA. Not sure if the cheaper version is different to the more expensive versions for GPS settings. I checked in "Tools" ,"Options" & under the tab , 3D view the Lat/Long is , as you mentioned , set at D.M.S. There are 2 other options. "Degrees" & "Universal Transverse". Tried both of these but neither improved the situation. In respect to the conversion , instead of sending a list which I am still compiling perhaps I could use as an example , a spot called Merries Reef , Southern tip. If your not aware this is near Boat Harbour at the northern end of Bate Bay The map reference I have is 34.03.000 / 151.11.23. Moving the Google curser to this reference & it sits at the Southern tip of Merries reef so in this case they pretty much line up. The Google reading being 34.03'00.00 / 151.11'23.00 The problem commences when the last 3 digits are greater than 600. Eg A map reference of 34.04.590 appear to line up OK with Google with a reading 34.04'59.00 but if the map reference is say , 34.04.610 Google , using 60 sec in a minuite ,rolls over to 34.05'01.00. In other words , Google only appears to jump out of sinc if the last 3 digits on the map reference is > 600. < 600 is OK. Looking foward to your comments Tks Geoff Link to comment Share on other sites More sharing options...
warnie Posted November 7, 2007 Share Posted November 7, 2007 The marks you have on your map are in Degrees Decimal minutes, which is the standard form used in australia send me the points and i will convert them for you Hi Netic...... Have always been under the impression that to convert from the google format to wgs84 was to divide the last 4 digits by 60 they then become the seconds.....ie 34.03'59.60 would convert to 34.03.993 my maths suck so how does this compare to your conversion for curosity..... i stand to be corrected and learn thanks oz... Cheers Warnie....... Link to comment Share on other sites More sharing options...
netic Posted November 7, 2007 Share Posted November 7, 2007 Warnie....mate i would know if that is correct i just use a program i have..... Geoff: mate although the location of looks good it will be around 270 metres out of sync The positon you have in DMM is 34.03.000S by 151.11.23.E The correct position in DMS is 34° 2'60.00"S by 151°11'13.80"E here is how the setiings on my google appear Link to comment Share on other sites More sharing options...
warnie Posted November 7, 2007 Share Posted November 7, 2007 The map reference I have is 34.03.000 / 151.11.23. Moving the Google curser to this reference & it sits at the Southern tip of Merries reef so in this case they pretty much line up. The Google reading being 34.03'00.00 / 151.11'23.00 Okay geoff... to test the conversion theory i thought it was pick another known example maybe greater than 600. the example up above reverts to 34.03.000 151.11.383 any one good at maths jump in would you please... Cheers Warnie........ Link to comment Share on other sites More sharing options...
Geoff Posted November 7, 2007 Author Share Posted November 7, 2007 Tks guy's Still trying to get my brain around the conversion aspect. Netic The screen you sent is the same as mine with one exception , "Show Lat/Long" yours has 4 options , mine has 3. DDM is missing. I assume you are working off the Pro version which is a higher version than Google Plus. Not to worry , will just need to live with that. The positon you have in DMM is 34.03.000S by 151.11.23.E Just to clarify , is DMM correct or a typo. From your previous post you mentioned maps as being DDM The correct position in DMS is 34° 2'60.00"S by 151°11'13.80"E Warnie Using your formula of 60 to convert the map reference of 34.03.000 / 151.11.2300 your calculation was 34.03.000 / 151.11.383. The 151 No. is very close to that advised by Netic but the 34 No. was not. Take the last 4 digits , 3000 divide by 60 = 50. 34.03.000 thus becoms , 34.03.50 so not sure where that leavs us. to test the conversion theory i thought it was pick another known example maybe greater than 600. Yes , your correct & I will come back with a few examples Regards Geoff Link to comment Share on other sites More sharing options...
warnie Posted November 8, 2007 Share Posted November 8, 2007 Tks guy's Still trying to get my brain around the conversion aspect. Warnie Using your formula of 60 to convert the map reference of 34.03.000 / 151.11.2300 your calculation was 34.03.000 / 151.11.383. The 151 No. is very close to that advised by Netic but the 34 No. was not. Take the last 4 digits , 3000 divide by 60 = 50. 34.03.000 thus becoms , 34.03.50 so not sure where that leavs us. Regards Geoff Hey geoff...maths my favourite subject....34.03.000 that already is the conversion from the google reading being 34.03'00.00... Cheers Warnie Link to comment Share on other sites More sharing options...
Geoff Posted November 8, 2007 Author Share Posted November 8, 2007 Went out this morning to run a few errands. Took the GPS & noted 4 spots which were easily located on Google where the last 3 digits were > 600. Using Warnie's suggestion of dividing the last 4 digits on Google by 60 for the spots I recorded , they all came in that close , the difference is negligible. Example Cnr Silverwater Rd (St HillersRd) & Parramatta Rd GPS , 33.50.724 / 151.02.494 Google , 33.50'43.34 / 151.02'29.87 Convert by 60 33.50.722 / 151.02.497. Conversely , if you have GPS map references & want to convert it to Google set to D.M.S. then multiply the last 3 digits by 6.0. Tks Warnie , this is good alternative for those with out Pro Geoff Link to comment Share on other sites More sharing options...
michaelrdoyle@gmail.com Posted November 8, 2007 Share Posted November 8, 2007 GPS , 33.50.724 / 151.02.494 Google , 33.50'43.34 / 151.02'29.87 Convert by 60 33.50.722 / 151.02.497. out of interest - what is the margin of error of "0.0.002" and "0.0.003"? (the difference in the two figures?) If it's a couple of meters - no worries. 10-20m and it can be a little off putting (say if you are looking for a very particular spot - note that normal margin of error with GPS is 5-10m). If it's over a hundred meters - the spot can be getting difficult to find.... Mike Link to comment Share on other sites More sharing options...
warnie Posted November 8, 2007 Share Posted November 8, 2007 out of interest - what is the margin of error of "0.0.002" and "0.0.003"? (the difference in the two figures?) If it's a couple of meters - no worries. 10-20m and it can be a little off putting (say if you are looking for a very particular spot - note that normal margin of error with GPS is 5-10m). If it's over a hundred meters - the spot can be getting difficult to find.... Mike Mike...fair question... every minute of latitude = 1 nautical mile ie 33.10.000 to 33.12.000 that there should be a differance of 2 nautical mile i then personally convert the last 3 digits to mtrs ...to be correct i know this to be the wrong unit of measurement but for example .500 which is half a nautical mile i just call it 500mtrs because i can relate and judge that distance easier than what i can judge .5 of a nautical mile its only a visual judgement for me.... for at the end of the day the vessel approaching the waypoint or cursor on the gps has the critical say...... so the differance between 2&3 of your last digit is very close to 1 mtr so as you say that would not rate a mention.... Ghee !!!!!! well thats what i have allways worked on so if that is not right some one enlighten me although im that used to that equation maybe you better not....just dont let me sail a yaucht..... Cheers Warnie.... Link to comment Share on other sites More sharing options...
Geoff Posted November 8, 2007 Author Share Posted November 8, 2007 Mike The other aspect is , where I placed the curser to where I actually was located when reading the GPS would have been out a few mt's. If you go to 33.50'43.34 / 151.02'29.87 in Google the actual location is the entry road into McDonalds off St Hillers Rd. Converting the GPS mark 33.50.724 = 33.50.4344. The curser only needs to move a fraction of a mm to change from 33.50.4334 to 33.50.4344. In other words it is not an error or correction of the calculation rather than having the curser on the exact spot I was parked when taking the GPS reading Geoff Link to comment Share on other sites More sharing options...
netic Posted November 8, 2007 Share Posted November 8, 2007 Man o man you guys are getting me confused........lol...... Thank god someone invented pc's so i can just do it there Link to comment Share on other sites More sharing options...
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