Averaging trackpoints

I've been looking at possible improvements in 'accuracy' that might
result from averaging track points. What I've been doing is placing the
GPS (a Geko 301) at a fixed point and setting it to record a track point
every 10 seconds. After an hour or so I download the track points using
DNR Garmin and then save them to a comma separated text file. Then I
load the file into OpenOffice Calc to calculate some descriptive
statistics for the data (using OSGB x,y coordinates; mean, sd, max, min
and median). The results are quite encouraging, even without using EGNOS
the mean x and the mean y seem to give me positions 'accurate' to
smaller than 3 meters.

However, looking at the data in Calc I have noticed an apparent anomaly.
Taking my last trial run as an example, I have 377 track points recorded
by the Geko in something over an hour of operation, but many of these
are identical. In other words, I have 377 points but these fall into
only 17 groups, with all of the points in one group containing identical
x and y data. It appears that the Geko only makes a change in the the
position it records when it 'thinks' it has moved by two or three metres
or more.

I'm sure there won't be a fix for this, but I'd be interested in any
opinions on why the Geko works in this way.

Regards,
Nick.

--
Nick Hopton,
Caversham, Reading, England.

I have done almost exactly the same test with a 76Cx and what I see is that
latitude, longitude and elevation change in an almost sine-wave pattern, but
at different frequencies among the three. Two similar tests at the exact
same position done three months apart showed the lat and lon averages to be
very close (ele was WAY out), but the total variation (min / max) were
noticably different.

Cooter wrote:


Here's what I get when I plot the track log, there are 377 individual
track points plotted here, remember. Is this the sort of thing you get?

http://www.hopton.dsl.pipex.com/shed.jpg

Regards,
Nick.

--
Nick Hopton,
Caversham, Reading, England.

Please excuse the long post, but I don't have a hosting site. Here are my
raw data - 1 hour @ 10 second intervals. Third column is elevation in feet.

34.1317273 -80.9824160 402.5769299
34.1317254 -80.9824161 402.5769299
34.1317260 -80.9824181 402.5769299
34.1317270 -80.9824174 402.5769299
34.1317278 -80.9824169 402.5769299
34.1317258 -80.9824147 404.1540720
34.1317253 -80.9824131 404.1540720
34.1317249 -80.9824159 405.7308135
34.1317242 -80.9824166 404.1540720
34.1317244 -80.9824180 404.1540720
34.1317234 -80.9824190 402.5769299
34.1317244 -80.9824209 400.9997878
34.1317271 -80.9824234 400.9997878
34.1317278 -80.9824244 400.9997878
34.1317286 -80.9824234 399.4230462
34.1317284 -80.9824218 397.8463047
34.1317276 -80.9824223 397.8463047
34.1317286 -80.9824221 397.8463047
34.1317290 -80.9824208 400.9997878
34.1317296 -80.9824197 404.1540720
34.1317289 -80.9824181 404.1540720
34.1317261 -80.9824166 405.7308135
34.1317217 -80.9824145 405.7308135
34.1317172 -80.9824125 405.7308135
34.1317138 -80.9824123 408.8846975
34.1317133 -80.9824109 413.6153226
34.1317100 -80.9824084 413.6153226
34.1317083 -80.9824064 416.7696068
34.1317056 -80.9824038 415.1924647
34.1317071 -80.9824041 415.1924647
34.1317085 -80.9824032 415.1924647
34.1317109 -80.9824017 413.6153226
34.1317125 -80.9823988 412.0385811
34.1317133 -80.9823969 410.4618393
34.1317129 -80.9823955 408.8846975
34.1317134 -80.9823943 407.3075554
34.1317131 -80.9823924 407.3075554
34.1317129 -80.9823867 399.4230462
34.1317147 -80.9823856 393.1148784
34.1317164 -80.9823854 391.5381369
34.1317178 -80.9823860 389.9609948
34.1317190 -80.9823851 389.9609948
34.1317195 -80.9823843 389.9609948
34.1317198 -80.9823853 389.9609948
34.1317234 -80.9823866 389.9609948
34.1317270 -80.9823892 394.6920205
34.1317271 -80.9823902 399.4230462
34.1317255 -80.9823912 402.5769299
34.1317232 -80.9823915 404.1540720
34.1317218 -80.9823933 408.8846975
34.1317218 -80.9823926 413.6153226
34.1317208 -80.9823932 416.7696068
34.1317213 -80.9823943 418.3463484
34.1317196 -80.9823932 415.1924647
34.1317171 -80.9823915 412.0385811
34.1317155 -80.9823902 410.4618393
34.1317141 -80.9823907 408.8846975
34.1317146 -80.9823912 405.7308135
34.1317155 -80.9823919 407.3075554
34.1317142 -80.9823913 407.3075554
34.1317105 -80.9823885 410.4618393
34.1317071 -80.9823876 408.8846975
34.1317050 -80.9823846 410.4618393
34.1317053 -80.9823845 412.0385811
34.1317089 -80.9823861 410.4618393
34.1317115 -80.9823871 404.1540720
34.1317124 -80.9823866 402.5769299
34.1317073 -80.9823858 402.5769299
34.1317042 -80.9823877 402.5769299
34.1317156 -80.9823895 400.9997878
34.1317192 -80.9823902 397.8463047
34.1317146 -80.9823901 397.8463047
34.1317119 -80.9823911 397.8463047
34.1317102 -80.9823922 399.4230462
34.1317145 -80.9823926 400.9997878
34.1317115 -80.9823936 400.9997878
34.1317083 -80.9823934 402.5769299
34.1317078 -80.9823941 400.9997878
34.1317068 -80.9823958 402.5769299
34.1317078 -80.9823988 400.9997878
34.1317079 -80.9824006 402.5769299
34.1317090 -80.9824021 399.4230462
34.1317103 -80.9824041 397.8463047
34.1317118 -80.9824035 396.2691626
34.1317129 -80.9824031 393.1148784
34.1317130 -80.9824037 391.5381369
34.1317135 -80.9824038 389.9609948
34.1317139 -80.9824082 388.3838527
34.1317119 -80.9824097 388.3838527
34.1317110 -80.9824104 388.3838527
34.1317113 -80.9824107 389.9609948
34.1317161 -80.9824120 388.3838527
34.1317198 -80.9824141 388.3838527
34.1317238 -80.9824162 386.8071111
34.1317281 -80.9824177 385.2303696
34.1317320 -80.9824176 383.6532275
34.1317337 -80.9824166 383.6532275
34.1317363 -80.9824161 385.2303696
34.1317385 -80.9824191 385.2303696
34.1317420 -80.9824197 383.6532275
34.1317458 -80.9824182 383.6532275
34.1317483 -80.9824160 383.6532275
34.1317502 -80.9824164 383.6532275
34.1317498 -80.9824147 386.8071111
34.1317503 -80.9824147 389.9609948
34.1317524 -80.9824145 389.9609948
34.1317515 -80.9824129 388.3838527
34.1317532 -80.9824146 386.8071111
34.1317590 -80.9824190 385.2303696
34.1317653 -80.9824218 385.2303696
34.1317651 -80.9824213 385.2303696
34.1317612 -80.9824161 385.2303696
34.1317576 -80.9824120 386.8071111
34.1317559 -80.9824104 386.8071111
34.1317518 -80.9824079 389.9609948
34.1317491 -80.9824068 391.5381369
34.1317472 -80.9824067 391.5381369
34.1317477 -80.9824058 389.9609948
34.1317455 -80.9824026 391.5381369
34.1317455 -80.9824032 389.9609948
34.1317452 -80.9824047 388.3838527
34.1317442 -80.9824045 389.9609948
34.1317439 -80.9824036 391.5381369
34.1317413 -80.9824033 394.6920205
34.1317389 -80.9824029 396.2691626
34.1317397 -80.9824052 396.2691626
34.1317401 -80.9824063 396.2691626
34.1317379 -80.9824051 396.2691626
34.1317357 -80.9824045 396.2691626
34.1317318 -80.9824021 399.4230462
34.1317263 -80.9823975 404.1540720
34.1317229 -80.9823950 407.3075554
34.1317185 -80.9823919 410.4618393
34.1317138 -80.9823885 413.6153226
34.1317120 -80.9823882 415.1924647
34.1317092 -80.9823874 415.1924647
34.1317054 -80.9823897 416.7696068
34.1317066 -80.9823933 413.6153226
34.1317063 -80.9823952 410.4618393
34.1317050 -80.9823948 408.8846975
34.1317054 -80.9823979 408.8846975
34.1317025 -80.9824024 410.4618393
34.1316984 -80.9824063 408.8846975
34.1316939 -80.9824030 405.7308135
34.1316928 -80.9824035 407.3075554
34.1316944 -80.9824041 404.1540720
34.1316928 -80.9824031 405.7308135
34.1316917 -80.9824004 407.3075554
34.1316923 -80.9823996 405.7308135
34.1316892 -80.9824020 408.8846975
34.1316912 -80.9824029 408.8846975
34.1316933 -80.9824047 405.7308135
34.1316942 -80.9824037 404.1540720
34.1316944 -80.9824045 405.7308135
34.1316944 -80.9824048 407.3075554
34.1316936 -80.9824058 407.3075554
34.1316942 -80.9824063 400.9997878
34.1316939 -80.9824037 396.2691626
34.1316953 -80.9824021 393.1148784
34.1316944 -80.9824006 393.1148784
34.1316927 -80.9823993 394.6920205
34.1316908 -80.9823975 396.2691626
34.1316892 -80.9823967 396.2691626
34.1316824 -80.9823843 400.9997878
34.1316716 -80.9823644 405.7308135
34.1316652 -80.9823501 412.0385811
34.1316633 -80.9823460 415.1924647
34.1316655 -80.9823467 415.1924647
34.1316700 -80.9823491 416.7696068
34.1316776 -80.9823532 421.5006326
34.1316819 -80.9823582 418.3463484
34.1316862 -80.9823651 412.0385811
34.1316897 -80.9823725 407.3075554
34.1316907 -80.9823752 404.1540720
34.1316912 -80.9823772 400.9997878
34.1316931 -80.9823827 396.2691626
34.1316953 -80.9823885 393.1148784
34.1316969 -80.9823912 391.5381369
34.1316965 -80.9823921 391.5381369
34.1316974 -80.9823910 388.3838527
34.1316971 -80.9823897 388.3838527
34.1316962 -80.9823880 389.9609948
34.1316967 -80.9823892 389.9609948
34.1316976 -80.9823886 389.9609948
34.1317006 -80.9823908 389.9609948
34.1317040 -80.9823980 386.8071111
34.1317077 -80.9824042 383.6532275
34.1317099 -80.9824073 382.0760854
34.1317123 -80.9824084 382.0760854
34.1317140 -80.9824099 380.4993439
34.1317159 -80.9824120 378.9226023
34.1317162 -80.9824131 378.9226023
34.1317141 -80.9824074 380.4993439
34.1317052 -80.9823881 389.9609948
34.1316995 -80.9823755 397.8463047
34.1316969 -80.9823724 400.9997878
34.1316927 -80.9823693 402.5769299
34.1316897 -80.9823654 404.1540720
34.1316897 -80.9823629 407.3075554
34.1316902 -80.9823632 399.4230462
34.1316896 -80.9823633 396.2691626
34.1316912 -80.9823627 393.1148784
34.1316919 -80.9823612 393.1148784
34.1316914 -80.9823613 394.6920205
34.1316910 -80.9823612 397.8463047
34.1316891 -80.9823581 408.8846975
34.1316891 -80.9823569 413.6153226
34.1316916 -80.9823587 410.4618393
34.1316950 -80.9823580 407.3075554
34.1316975 -80.9823509 408.8846975
34.1317000 -80.9823477 407.3075554
34.1317027 -80.9823480 404.1540720
34.1317053 -80.9823486 400.9997878
34.1317073 -80.9823473 400.9997878
34.1317061 -80.9823502 402.5769299
34.1317028 -80.9823602 407.3075554
34.1317005 -80.9823667 408.8846975
34.1317032 -80.9823717 407.3075554
34.1316995 -80.9823823 410.4618393
34.1317052 -80.9823844 405.7308135
34.1317089 -80.9823879 402.5769299
34.1317098 -80.9823885 400.9997878
34.1317125 -80.9823905 400.9997878
34.1317141 -80.9823918 400.9997878
34.1317126 -80.9823928 402.5769299
34.1317138 -80.9823859 397.8463047
34.1317142 -80.9823864 394.6920205
34.1317175 -80.9823993 391.5381369
34.1317209 -80.9824088 388.3838527
34.1317228 -80.9824167 386.8071111
34.1317234 -80.9824290 382.0760854
34.1317291 -80.9824276 375.7683181
34.1317300 -80.9824289 372.6148348
34.1317260 -80.9824346 372.6148348
34.1317235 -80.9824390 372.6148348
34.1317195 -80.9824384 375.7683181
34.1317217 -80.9824302 374.1915766
34.1317242 -80.9824185 374.1915766
34.1317211 -80.9824139 377.3454602
34.1317181 -80.9824120 380.4993439
34.1317159 -80.9824082 385.2303696
34.1317130 -80.9824042 389.9609948
34.1317094 -80.9824003 393.1148784
34.1317051 -80.9823985 399.4230462
34.1317017 -80.9823879 405.7308135
34.1317058 -80.9823699 400.9997878
34.1317048 -80.9823617 399.4230462
34.1316933 -80.9823679 407.3075554
34.1316926 -80.9823653 410.4618393
34.1316902 -80.9823651 413.6153226
34.1316861 -80.9823675 418.3463484
34.1316799 -80.9823771 419.9230899
34.1316757 -80.9823814 421.5006326
34.1316755 -80.9823827 423.0777747
34.1316741 -80.9823825 424.6545162
34.1316721 -80.9823824 427.8083998
34.1316695 -80.9823797 430.9622835
34.1316705 -80.9823839 429.3855420
34.1316729 -80.9823879 426.2312577
34.1316774 -80.9823953 423.0777747
34.1316838 -80.9824005 421.5006326
34.1316856 -80.9824047 419.9230899
34.1316659 -80.9824092 432.5390250
34.1316536 -80.9824114 440.4239344
34.1316528 -80.9824151 440.4239344
34.1316554 -80.9824227 437.2700507
34.1316648 -80.9824341 430.9622835
34.1316720 -80.9824394 426.2312577
34.1316774 -80.9824380 423.0777747
34.1316819 -80.9824364 419.9230899
34.1316888 -80.9824368 415.1924647
34.1316948 -80.9824352 413.6153226
34.1316922 -80.9824322 416.7696068
34.1316902 -80.9824349 418.3463484
34.1316869 -80.9824395 419.9230899
34.1316851 -80.9824441 418.3463484
34.1316848 -80.9824437 419.9230899
34.1316871 -80.9824468 416.7696068
34.1316882 -80.9824451 416.7696068
34.1316870 -80.9824325 421.5006326
34.1316893 -80.9824213 423.0777747
34.1316921 -80.9824166 424.6545162
34.1316952 -80.9824145 424.6545162
34.1316968 -80.9824104 426.2312577
34.1316980 -80.9824108 426.2312577
34.1317010 -80.9824146 421.5006326
34.1317047 -80.9824146 416.7696068
34.1317048 -80.9824141 415.1924647
34.1317063 -80.9824115 412.0385811
34.1317105 -80.9824125 408.8846975
34.1317164 -80.9824177 404.1540720
34.1317264 -80.9824234 397.8463047
34.1317582 -80.9824245 375.7683181
34.1317678 -80.9824258 369.4605509
34.1317700 -80.9824208 366.3066672
34.1317695 -80.9824204 364.7295251
34.1317711 -80.9824288 364.7295251
34.1317736 -80.9824425 364.7295251
34.1317726 -80.9824506 364.7295251
34.1317688 -80.9824538 366.3066672
34.1317636 -80.9824537 369.4605509
34.1317617 -80.9824540 367.8838090
34.1317627 -80.9824532 367.8838090
34.1317648 -80.9824539 366.3066672
34.1317659 -80.9824590 363.1523830
34.1317670 -80.9824616 361.5756415
34.1317664 -80.9824602 361.5756415
34.1317621 -80.9824565 366.3066672
34.1317571 -80.9824534 371.0376930
34.1317558 -80.9824511 374.1915766
34.1317564 -80.9824499 374.1915766
34.1317543 -80.9824441 377.3454602
34.1317515 -80.9824419 380.4993439
34.1317476 -80.9824369 383.6532275
34.1317415 -80.9824397 386.8071111
34.1317410 -80.9824423 385.2303696
34.1317421 -80.9824387 378.9226023
34.1317435 -80.9824368 377.3454602
34.1317444 -80.9824385 374.1915766
34.1317467 -80.9824395 371.0376930
34.1317419 -80.9824366 372.6148348
34.1317363 -80.9824330 377.3454602
34.1317311 -80.9824299 380.4993439
34.1317285 -80.9824291 383.6532275
34.1317258 -80.9824320 383.6532275
34.1317211 -80.9824341 388.3838527
34.1317178 -80.9824372 389.9609948
34.1317164 -80.9824384 393.1148784
34.1317157 -80.9824399 394.6920205
34.1317150 -80.9824390 394.6920205
34.1317142 -80.9824394 394.6920205
34.1317131 -80.9824394 396.2691626
34.1317135 -80.9824403 396.2691626
34.1317140 -80.9824399 394.6920205
34.1317169 -80.9824402 393.1148784
34.1317175 -80.9824398 391.5381369
34.1317203 -80.9824357 389.9609948
34.1317217 -80.9824328 388.3838527
34.1317223 -80.9824306 386.8071111
34.1317221 -80.9824304 385.2303696
34.1317237 -80.9824326 382.0760854
34.1317273 -80.9824352 380.4993439
34.1317327 -80.9824373 378.9226023
34.1317367 -80.9824399 374.1915766
34.1317389 -80.9824402 371.0376930
34.1317393 -80.9824395 371.0376930
34.1317419 -80.9824420 367.8838090
34.1317457 -80.9824430 366.3066672
34.1317493 -80.9824542 367.8838090
34.1317508 -80.9824508 366.3066672
34.1317519 -80.9824497 366.3066672
34.1317523 -80.9824485 366.3066672
34.1317539 -80.9824473 364.7295251
34.1317535 -80.9824440 364.7295251
34.1317522 -80.9824385 366.3066672
34.1317512 -80.9824362 366.3066672
34.1317493 -80.9824336 367.8838090
34.1317468 -80.9824290 369.4605509
34.1317444 -80.9824254 371.0376930
34.1317432 -80.9824244 372.6148348
34.1317405 -80.9824245 374.1915766
34.1317378 -80.9824259 375.7683181
34.1317379 -80.9824244 375.7683181
34.1317398 -80.9824200 374.1915766
34.1317404 -80.9824149 372.6148348
34.1317399 -80.9824124 371.0376930
34.1317392 -80.9824090 369.4605509
34.1317394 -80.9824057 367.8838090
34.1317374 -80.9824057 364.7295251
34.1317397 -80.9823988 363.1523830
34.1317420 -80.9823955 363.1523830
34.1317431 -80.9823954 359.9988996
34.1317425 -80.9823950 358.4217575
34.1317430 -80.9823949 359.9988996
34.1317446 -80.9823945 358.4217575
34.1317499 -80.9823950 359.9988996
34.1317545 -80.9823945 359.9988996
34.1317545 -80.9824041 355.2678739
34.1317558 -80.9824100 353.6911324
34.1317576 -80.9824133 352.1139903
34.1317596 -80.9824174 350.5368482
34.1317591 -80.9824197 348.9601066
34.1317555 -80.9824197 350.5368482
34.1317556 -80.9824228 350.5368482
34.1317571 -80.9824260 350.5368482
34.1317653 -80.9824249 355.2678739
34.1317687 -80.9824192 361.5756415
34.1317694 -80.9824123 364.7295251
34.1317696 -80.9824060 369.4605509
34.1317662 -80.9824015 372.6148348
34.1317622 -80.9824000 372.6148348
34.1317594 -80.9823985 374.1915766
34.1317617 -80.9824026 375.7683181
34.1317622 -80.9824064 374.1915766
34.1317627 -80.9824099 372.6148348
34.1317687 -80.9824221 369.4605509
34.1317731 -80.9824328 366.3066672
34.1317766 -80.9824433 364.7295251
34.1317812 -80.9824508 364.7295251
34.1317861 -80.9824649 359.9988996
34.1317958 -80.9825006 353.6911324
34.1318110 -80.9825202 355.2678739
34.1318144 -80.9825214 356.8446157
34.1318145 -80.9825218 358.4217575
34.1318100 -80.9825161 359.9988996
34.1318026 -80.9825071 363.1523830
34.1317975 -80.9825040 363.1523830
34.1317939 -80.9825034 363.1523830
34.1317897 -80.9825001 363.1523830
34.1317805 -80.9825046 359.9988996
34.1317752 -80.9825047 356.8446157
34.1317757 -80.9825015 353.6911324
34.1317773 -80.9824943 350.5368482
34.1317766 -80.9824832 350.5368482
34.1317757 -80.9824741 350.5368482
34.1317752 -80.9824695 353.6911324
34.1317737 -80.9824674 358.4217575
34.1317732 -80.9824657 361.5756415
34.1317716 -80.9824607 364.7295251
34.1317662 -80.9824509 371.0376930
34.1317622 -80.9824467 375.7683181
34.1317631 -80.9824520 374.1915766
34.1317637 -80.9824584 374.1915766
34.1317652 -80.9824632 375.7683181
34.1317626 -80.9824632 377.3454602
34.1317617 -80.9824644 377.3454602
34.1317550 -80.9824560 378.9226023
34.1317545 -80.9824571 377.3454602
34.1317556 -80.9824605 374.1915766
34.1317560 -80.9824612 374.1915766
34.1317569 -80.9824613 374.1915766
34.1317570 -80.9824578 374.1915766
34.1317610 -80.9824607 372.6148348
34.1317642 -80.9824657 369.4605509
34.1317621 -80.9824600 367.8838090
34.1317580 -80.9824473 369.4605509
34.1317537 -80.9824379 372.6148348
34.1317488 -80.9824316 377.3454602
34.1317428 -80.9824234 383.6532275
34.1317358 -80.9824086 389.9609948
34.1317336 -80.9824006 394.6920205
34.1317380 -80.9824057 391.5381369
34.1317420 -80.9824109 388.3838527
34.1317331 -80.9823968 404.1540720
34.1317255 -80.9823941 407.3075554
34.1317250 -80.9823993 404.1540720
34.1317306 -80.9824022 405.7308135
34.1317346 -80.9823986 408.8846975
34.1317368 -80.9823990 412.0385811
34.1317368 -80.9823958 416.7696068
34.1317367 -80.9823991 413.6153226
34.1317378 -80.9824047 408.8846975
34.1317349 -80.9824108 402.5769299
34.1317364 -80.9824161 399.4230462
34.1317378 -80.9824211 394.6920205
34.1317364 -80.9824182 396.2691626
34.1317368 -80.9824200 396.2691626
34.1317426 -80.9824310 394.6920205
34.1317766 -80.9824752 393.1148784
34.1317782 -80.9824801 391.5381369
34.1317415 -80.9824358 424.6545162
34.1317296 -80.9824177 434.1161671
34.1316923 -80.9823850 440.4239344
34.1316924 -80.9823958 432.5390250
34.1317022 -80.9824099 440.4239344
34.1317072 -80.9824089 438.8467923

Cooter wrote:


There doesn't appear to be one lat/long coordinate in this set that is
identical to another, which is not what I get. In fact, what you're
getting is what I was hoping to get with the Geko. All interesting
stuff, nevertheless.

Regards,
Nick.

--
Nick Hopton,
Caversham, Reading, England.