Skimmer frequency accuracy
To be a good RBN citizen a skimmer should have a frequency accuracy of 2ppm or better.
VERY IMPORTANT: To use the data below to improve the accuracy of your skimmer, multiply the current value of FreqCalibration in your skimmer software’s settings file with the suggested adjustment factor listed below.
The location of the settings files are:
CW Skimmer Server: %appdata%\Afreet\Products\SkimSrv\SkimSrv.ini
CW Skimmer: %appdata%\Afreet\Products\CwSkimmer\CwSkimmer.ini
The data listed below is based on yesterday’s RBN data, 00:00 to 23:59 UTC. This means that when making adjustments, changes in calibration will typically not have full impact on the listed data until the second day after the change.
The deviation estimates are based on spots on all active bands (40m and higher) from the respective skimmer. If different hardware is used for the different bands, the deviation number may thus not represent the actual deviation for a particular band. It is a good practice to run a separate instance of RBN Aggregator with a unique SSID for each hardware, (SM7IUN-1, SM7IUN-2, etc.)
A link to the software used to produce the tables can be found at the bottom of this page. It runs as a cron job in an Ubuntu container on my Synology server and uploads to this WordPress website shortly after midnight UTC daily.
The deviation estimation is done in two steps. The first step uses a small number of highly accurate skimmers (called “anchors” in the code, typically GPSDO-controlled skimmers) as reference. The whole estimation process is then repeated one more time but using both the anchors as well as all skimmers determined to be the “good” as reference. The “good” skimmers are those with less than 0.15ppm average deviation from the anchors, producing more than 100 qualifying spots (the qualification criteria of spots are outlined below.)
Repeating the analysis with this this extended set of skimmers as frequency references drastically increases the geographical coverage of the analysis thereby increasing the number of qualifying spots which means a much more reliable deviation estimates for all skimmers. The skimmers used as reference skimmers in the second stage (i.e. both anchors and “good”) are marked with an asterisk in the table below.
When looking at the numbers, keep in mind that the deviations estimated by the algorithm are 100 to 1000 times smaller than the 100Hz resolution of RBN frequency data. The input data is thus extremely “noisy” which inevitably leads to statistical variations. This is also the reason for not including spots under a certain frequency. Doing so would skew the statistics and cause underestimation of the frequency error.
Due to propagation characteristics, operator behavior (e.g. small QSY), and just statistical variations due to the 100Hz rounding, some skimmers selected as reference skimmers in the first stage may have more than 0.2ppm deviation in the second stage. This is not an error.
If you do not see your skimmer in the list below in spite of it successfully feeding spots to RBN the most likely reason is that it is off in frequency. The analytics discards all spots from skimmers having more than 0.5kHz frequency error.
if you want to implement an automated calibration of your skimmer you can access the skew data in machine-readable CSV format here https://sm7iun.se/rbnskew.csv
An skimmer calibration automation based on Windows PowerShell can be found here. It scrapes the calibration adjustment from this page and can be configured to update two CW Skimmer Server instances, two RTTY Skimmer Servers, and one CWSL_DIGI instance.
796381 RBN spots between 2026-06-07 00:00 and 23:59 UTC. 279508 spots (35.1%) were from reference skimmers (*). Average spot flow was 553 per minute from 219 active CW skimmers. 445680 spots from 215 skimmers qualified for analysis by meeting the following criteria: * Mode of spot is CW. * Also spotted by a reference skimmer within 1000 spots. * Also spotted by a reference skimmer within 10s. * SNR is 3dB or higher. * Frequency is 7000kHz or higher. * Frequency deviation from reference skimmer is 0.5kHz or less. * At least 5 spots from same skimmer in data set. Skimmer [ppm] Spots Adjustment ------------------------------------- 5Z4GO +0.2 251 1.000000237 9M2CNC +0.4 161 1.000000389 AA0O -4.0 36 0.999996040 AA4PA* +0.1 945 1.000000110 AC0C-1* -0.1 1794 0.999999899 AK6RI-1 -0.2 196 0.999999827 BA6KC* -0.0 595 0.999999990 BD4UNT +0.1 208 1.000000057 BD7JNA +0.0 25 1.000000000 BD8CS* -0.0 1342 0.999999955 BG2TFW -0.1 91 0.999999948 BH4RRG +0.0 106 1.000000000 BH4RRG0 +0.1 121 1.000000138 BH4XDZ +0.0 110 1.000000043 BI4MPH +0.0 254 1.000000028 BI7JMD -0.0 129 0.999999963 CT1EYQ -0.6 2841 0.999999432 DC8YZ +0.2 2877 1.000000244 DD0VS +0.6 438 1.000000587 DE1LON -0.2 4195 0.999999772 DF7GB* +0.0 4964 1.000000039 DK0TE +0.7 4909 1.000000689 DK3UA +1.3 1531 1.000001301 DK3WW* +0.0 6197 1.000000041 DK8NE +0.0 19 1.000000000 DK9IP -11.4 3233 0.999988600 DK9IP-1 -10.9 3860 0.999989113 DL0LA* -0.0 3470 0.999999999 DL1HWS +1.2 5640 1.000001189 DL1HWS-3 +1.7 3331 1.000001721 DL1HWS-4 +1.3 446 1.000001307 DL5RCN +14.2 665 1.000014184 DL5RMH +3.7 4131 1.000003670 DL8LAS +1.1 7884 1.000001073 DL8LAS-1 +0.3 6075 1.000000256 DL8TG* -0.1 4319 0.999999917 DM5GG +1.8 4644 1.000001767 DO4DXA* +0.0 3147 1.000000024 DP5G* -0.1 4825 0.999999905 DR4W -1.1 6169 0.999998915 DR5X +2.3 5220 1.000002337 EA1DAV* -0.0 3274 0.999999974 EA2CW -0.4 110 0.999999561 EA2RCF-4 +0.7 2791 1.000000667 EA5WU* -0.1 6299 0.999999930 EA8/DF4UE* +0.1 5930 1.000000128 EI4HQ* -0.1 6597 0.999999929 ES2RR* -0.0 3983 0.999999970 ES5PC -0.0 84 1.000000000 F4BPO +1.1 2579 1.000001073 F4GOU -0.3 4657 0.999999749 F5AHD +3.4 935 1.000003428 F6IIT -2.0 14 0.999997966 F6KGL +0.3 1934 1.000000270 F8DGY -4.8 4187 0.999995167 G0KTN +0.2 4635 1.000000239 G0TMX +4.3 251 1.000004347 G4HDS +0.5 209 1.000000477 G4IRN +0.4 5852 1.000000434 G4KCM* -0.1 3019 0.999999945 G4ZFE -1.5 5169 0.999998543 GI4DOH -0.2 2923 0.999999761 GX0FRE* +0.0 4499 1.000000021 HA1VHF +0.8 3587 1.000000762 HA2NA* +0.1 3872 1.000000136 HA8TKS* +0.1 3201 1.000000072 HB9BXE +0.3 3337 1.000000317 HB9DCO -0.5 4055 0.999999493 HB9EMP -0.3 445 0.999999664 HB9GVO +0.6 1031 1.000000610 HB9YC-SDR +0.5 1537 1.000000512 HG8A +3.8 5194 1.000003800 HS0ZGZ +0.2 198 1.000000182 IK3STG +2.2 1989 1.000002151 IK4VET +4.3 5982 1.000004314 IK7YTT* +0.0 2645 1.000000011 IQ9RG* +0.1 1399 1.000000069 IT9GSF* -0.0 8177 0.999999952 IZ2CPS* -0.1 2102 0.999999912 IZ8EYP* -0.1 1100 0.999999943 JA1CCA -0.8 118 0.999999182 JE2YCR +0.6 23 1.000000621 JH7CSU1 +1.7 276 1.000001724 JI1HFJ -1.7 125 0.999998341 JJ2VLY +1.2 344 1.000001201 JK1QLQ +0.1 46 1.000000078 JN1ILK +2.1 993 1.000002054 K1RA +2.4 2522 1.000002404 K1RA-4* +0.2 1672 1.000000154 K3GMQ* -0.1 1586 0.999999947 K3PA-1 +0.3 1466 1.000000290 K3PA-2 +0.0 24 1.000000000 K4PP +0.3 525 1.000000326 K5EM +5.1 351 1.000005099 K5TR -0.4 1227 0.999999608 K7CO +1.2 476 1.000001188 K7EK +2.4 403 1.000002405 K7RUT +15.6 147 1.000015555 K9IMM* -0.0 1357 0.999999963 K9LC +0.6 979 1.000000579 KC4YVA +0.8 927 1.000000825 KD2OGR +0.0 7 1.000000000 KD7EFG +0.3 617 1.000000253 KH6LC +0.1 74 1.000000096 KM3T-2 +0.5 649 1.000000538 KM3T-3* +0.0 2939 1.000000004 KM3T-5* -0.0 2866 0.999999979 KO4BHX +0.2 2505 1.000000227 KW7MM +0.4 1215 1.000000360 KW7MM-2 +0.3 1052 1.000000325 KW7MM-3 +0.3 122 1.000000302 LA6TPA +0.3 1175 1.000000299 LB9KJ -0.6 1636 0.999999407 LB9KJ-2 +1.3 22 1.000001330 LZ3CB* -0.1 3027 0.999999929 LZ4AE +0.9 9673 1.000000855 LZ4UX* +0.0 4395 1.000000014 LZ5DI +3.0 5116 1.000003037 LZ7AA +0.6 4402 1.000000576 M1GEO +5.9 5625 1.000005923 MM0ZBH* +0.1 7839 1.000000128 MM9PSY* -0.1 5754 0.999999937 N2CR +0.6 370 1.000000594 N2YCH +1.8 1527 1.000001792 N5RZ +4.9 1452 1.000004881 N6TV +0.2 356 1.000000223 N7VVX +0.2 102 1.000000166 N9CO* +0.0 704 1.000000027 ND7K* -0.3 779 0.999999714 NG7M -0.0 272 0.999999953 NN3RP +0.0 34 1.000000000 NU4F* -0.0 983 1.000000000 OE3KLU +0.0 12 1.000000001 OE9GHV* -0.0 5820 0.999999956 OH4KA +0.9 294 1.000000860 OH6BG* +0.0 4503 1.000000030 OK1FCJ +0.7 5843 1.000000656 OK1HRA -4.2 4561 0.999995806 ON6ZQ +0.2 4945 1.000000187 OZ1AAB* -0.1 1496 0.999999941 OZ1BZS +0.9 273 1.000000869 PA5KT-4 -0.2 5039 0.999999755 PE5TT +0.3 3894 1.000000263 PI4CC* -0.0 6081 0.999999951 PT2FHC +0.0 152 1.000000026 PY2KNK +3.5 341 1.000003525 PY2PE +0.2 145 1.000000197 R4NCU -0.6 1268 0.999999443 RK3TD +0.7 3458 1.000000681 RK3TD-2 +0.7 3122 1.000000693 RN4WA +1.1 772 1.000001091 RU9CZD* +0.1 4469 1.000000112 S50U* -0.1 2948 0.999999937 S53WW +0.2 596 1.000000191 S54L +2.4 5446 1.000002446 S58W* +0.0 1036 1.000000034 SE5E* -0.1 7070 0.999999909 SM0TCZ +0.5 356 1.000000501 SM1HEV* +0.1 2426 1.000000095 SM7IUN* -0.0 3757 0.999999950 SP5GQ* +0.1 4366 1.000000142 SQ5J +8.4 4950 1.000008385 SV1CDN -0.5 295 0.999999500 SZ1A +2.2 2135 1.000002151 TF3Y +1.8 2455 1.000001823 TI7W +1.3 528 1.000001313 UT5R* +0.1 2507 1.000000108 UY2RA -1.2 710 0.999998789 V51YJ +2.0 69 1.000001958 VE3EID +0.5 1595 1.000000467 VE6AO -0.4 220 0.999999622 VE6JY +1.0 847 1.000000956 VE6WZ -1.1 778 0.999998915 VE6WZ-3 -1.1 746 0.999998923 VE7CC +0.7 144 1.000000665 VK2GEL +0.8 9 1.000000792 VK2RH +0.0 17 1.000000000 VK3RASA -0.1 138 0.999999889 VK6ANC +0.0 74 1.000000000 VU22DX +0.1 85 1.000000084 VU2CPL-1 +0.3 59 1.000000281 VU2OY +0.2 263 1.000000234 VU2PTT -0.6 93 0.999999373 VU2TUM +0.9 657 1.000000938 W1NT-2 +0.4 1498 1.000000403 W1NT-6 +0.4 3049 1.000000424 W2MV +0.1 313 1.000000114 W2NNN +3.8 1150 1.000003786 W3LPL -0.4 1342 0.999999633 W3OA* +0.2 959 1.000000152 W3RGA* +0.1 1891 1.000000077 W3UA -0.1 38 0.999999906 W4KAZ* +0.2 1160 1.000000182 W6YX* +0.2 696 1.000000208 W8WTS* +0.0 574 1.000000033 WA7LNW -3.9 763 0.999996080 WB6BEE* +0.0 2029 1.000000001 WC2L +0.9 39 1.000000914 WE9V +0.2 1306 1.000000246 WF8Z +2.8 90 1.000002798 WS2C +9.5 414 1.000009530 WS3W* +0.1 428 1.000000117 WT8P -0.0 148 0.999999952 WT9U* -0.0 696 0.999999964 WX7V/5 +0.3 129 1.000000306 WZ7I +0.5 2953 1.000000500 YO2CK* -0.1 4164 0.999999928 YO2KAR -0.2 1701 0.999999764 YO5LD +1.2 4908 1.000001196 ZF1A -0.2 1040 0.999999849 ZF9CW +0.4 2628 1.000000373 ZL2KS +1.5 164 1.000001507 ZL3X -0.4 561 0.999999617 ZL4YL +0.5 841 1.000000455 ZS1NN -5.0 86 0.999995045 Last updated 2026-06-08 00:16:13 UTC
Historical skimmer frequency accuracy
Below you will find historical accuracy data for the past ten days. Do not be concerned over minor daily variations. Since RBN spots only have 100Hz frequency accuracy, the input data is very noisy. Even for a perfectly accurate skimmer, the typical RMS rounding error across all shortwave bands is around 3ppm. This means that for a skimmer with 1000 spots per day the statistical variation is up to 0.2ppm. For skimmers with less than 100 spots per day the statistical variation can be above 2ppm. The content of the table below is based on the historical content of the above table.
Skimmer 0607 0606 0605 0604 0603 0602 0601 0531 0530 0529 --------------------------------------------------------------------- 3D2AG +0.5 +0.3 +0.4 +0.3 +0.1 +0.2 +0.1 5Z4GO +0.2 +0.6 +0.1 +0.2 +0.5 +0.6 +0.6 +0.6 +0.0 9M2CNC +0.4 +0.5 +0.3 +0.3 +0.6 +0.7 +0.8 +0.6 +0.5 +0.2 AA0O -4.0 -6.6 -6.0 -6.3 -5.0 -6.9 -5.0 AA4PA +0.1 +0.1 +0.0 +0.1 +0.1 +0.2 +0.2 +0.2 +0.2 -0.2 AC0C-1 -0.1 -0.0 -0.1 -0.1 -0.1 AK6RI-1 -0.2 -0.0 +0.0 -0.3 +0.0 +0.1 -0.0 -0.0 -0.0 -0.1 BA6KC -0.0 +0.0 -0.1 -0.0 +0.0 +0.1 -0.0 +0.1 +0.0 -0.1 BD4UNT +0.1 +0.1 +0.2 +0.1 +0.3 +0.1 +0.1 +0.2 +0.2 +0.1 BD7JNA +0.0 +0.1 -0.1 +0.3 +0.2 +0.4 +0.4 +0.1 -0.0 +0.2 BD8CS -0.0 -0.1 +0.0 +0.0 +0.0 -0.0 -0.0 +0.0 -0.0 -0.1 BG0AJO/0 +0.0 +0.3 +0.2 -0.1 +0.0 +0.1 +0.2 +0.8 BG2TFW -0.1 -0.2 +0.0 +0.0 +0.2 +0.0 +0.0 +0.7 +0.7 +1.3 BH4HKZ +0.3 +0.0 BH4RRG +0.0 +0.0 +0.0 +0.3 +0.0 +0.0 +0.1 +0.1 +0.1 BH4RRG0 +0.1 +0.2 +0.0 +0.4 +0.3 +0.0 +0.8 +0.4 +0.3 +0.3 BH4XDZ +0.0 +0.3 +0.0 -0.1 +0.0 +0.0 +0.0 +0.0 -0.0 -0.0 BI4MPH +0.0 +0.0 +0.1 +0.2 +0.2 +0.3 -0.0 +0.2 +0.2 +0.2 BI7JMD -0.0 -0.1 +0.0 +0.1 +0.0 -0.1 -0.3 +0.0 +0.1 +0.0 CT1EYQ -0.6 -0.4 -0.5 -0.4 -0.3 -0.4 -0.1 -0.2 -0.2 -0.1 CX7ACH +16.1 +16.1 DC8YZ +0.2 +0.1 +0.1 +0.2 +0.1 +0.1 -0.0 +0.1 +0.1 -0.0 DD0VS +0.6 +0.5 DE1LON -0.2 -0.2 -0.1 -0.2 -0.1 -0.1 -0.0 -0.2 -0.3 -0.3 DF7GB +0.0 -0.0 -0.0 +0.0 -0.0 -0.0 +0.1 -0.0 +0.0 +0.0 DK0TE +0.7 +0.8 +0.4 +0.5 +0.4 +0.5 +0.2 +1.5 +1.5 +0.8 DK3UA +1.3 -0.3 +0.0 +0.4 -0.4 DK3WW +0.0 +0.1 +0.1 +0.2 +0.2 +0.2 +0.2 +0.8 +0.7 +0.1 DK8NE +0.0 -0.0 -0.2 DK9IP-1 -10.9 -12.0 -11.5 -5.6 +0.0 +0.1 +0.0 +0.1 +0.1 +0.1 DK9IP -11.4 -12.3 -11.9 -5.9 -0.0 +0.1 +0.0 +0.1 +0.1 -0.0 DL0LA -0.0 +0.0 -0.0 -0.0 +0.0 -0.0 +0.1 +0.1 +0.1 +0.1 DL1GME +1.0 DL1HWS +1.2 +1.2 +0.8 +0.8 +1.1 +0.9 +0.9 +1.5 +1.4 +0.9 DL1HWS-3 +1.7 +1.6 +1.2 +1.4 +1.6 +1.3 +1.3 +2.1 +2.1 +1.6 DL1HWS-4 +1.3 +0.9 +0.6 +1.5 +1.5 +1.3 +0.8 +2.0 +1.2 +1.3 DL3OBQ -7.9 -7.1 -7.3 -7.4 DL5RCN +14.2 +14.1 +13.9 +14.3 DL5RMH +3.7 +3.4 DL8LAS-1 +0.3 +0.4 +0.2 +0.4 +0.5 +0.5 +0.3 +0.3 +0.4 +0.3 DL8LAS +1.1 +1.1 +0.9 +1.1 +1.5 +1.4 +1.7 +1.8 +1.4 DL8LAS-3 +3.8 DL8TG -0.1 -0.9 -1.6 -0.0 -0.0 -0.0 +0.1 +0.0 -0.0 DM5GG +1.8 +1.6 DM6EE +0.3 -0.0 -0.9 -0.1 -0.0 +0.0 -0.0 +0.0 DO4DXA +0.0 +0.1 +0.0 +0.0 +0.0 +0.0 +0.1 +0.1 +0.1 +0.1 DP5G -0.1 -0.1 -0.0 -0.0 -0.1 -0.0 -0.1 -0.1 -0.1 -0.1 DR4W -1.1 -0.7 -1.0 -1.6 -1.7 -1.0 -0.8 -1.4 -1.0 -1.2 DR5X +2.3 +2.3 +2.1 +2.4 +2.1 +1.6 +2.2 +3.1 +3.4 +2.9 E28AC +0.0 +0.5 +0.8 +0.8 +0.0 EA1DAV -0.0 -0.0 -0.0 +0.0 +0.0 -0.0 -0.0 +0.1 +0.1 -0.0 EA2CW -0.4 -0.3 +0.1 +0.2 +0.2 +0.0 +0.2 +0.2 +0.2 +0.2 EA2RCF-4 +0.7 +0.8 +0.5 +0.6 +0.8 +0.7 +0.8 +1.4 +1.6 +1.0 EA5WU -0.1 -0.0 -0.0 +0.0 -0.0 +0.0 -0.1 +0.0 +0.0 -0.0 EA8/DF4UE +0.1 +0.0 +0.1 +0.1 +0.1 -3.3 -5.7 -6.7 EA/VE3NZ -0.1 EI4HQ -0.1 -0.0 -0.1 -0.0 -0.0 -0.0 +0.0 +0.0 -0.0 -0.0 ES2RR -0.0 -0.0 -0.0 +0.0 +0.0 -0.0 -0.1 +0.0 +0.0 -0.0 ES5PC -0.0 -0.0 +0.0 -0.0 -0.0 -0.0 +0.0 EU1ST +5.5 EU8RO +0.5 +0.5 EY8ZE +4.3 +0.2 -0.0 -0.1 -0.1 F4BPO +1.1 +0.3 F4GOU -0.3 -0.3 -0.1 -0.3 -0.3 -0.3 -0.1 +0.0 +0.4 +0.5 F4VVG +0.0 -0.1 +0.0 -0.2 -0.3 -0.1 F5AHD +3.4 +3.4 +2.7 +2.4 +4.2 +3.6 F6IIT -2.0 -1.5 +0.0 +0.0 +0.0 -0.1 +0.0 +0.2 F6KGL +0.3 +0.2 +0.3 +0.1 F8DGY -4.8 -4.6 -4.8 +0.3 G0KTN +0.2 +0.4 +0.3 +0.2 +0.4 +0.4 +0.4 +0.6 +0.5 +0.3 G0TMX +4.3 +0.5 +0.7 +0.7 G3YPP +0.2 -0.3 -0.0 +1.3 +1.1 +0.3 G4HDS +0.5 +0.3 +0.2 -8.1 G4IRN +0.4 +0.5 +0.4 +0.4 +0.4 +0.3 +0.4 +0.6 +0.6 +0.4 G4KCM -0.1 +0.0 +0.0 -0.0 -0.0 -0.0 +0.1 -0.0 -0.0 -0.1 G4ZFE -1.5 -1.1 -0.7 -0.7 -0.8 -0.6 -0.6 -1.0 -0.6 -0.2 GI4DOH -0.2 -0.2 -0.1 -0.1 +0.0 +0.2 +0.2 +0.2 +0.2 +0.0 GX0FRE +0.0 +0.1 +0.2 +0.0 +0.1 +0.2 +0.3 +0.4 +0.5 +0.3 HA1VHF +0.8 +0.9 +0.6 +0.7 +0.7 +0.7 +0.7 +1.2 +1.3 +0.8 HA2NA +0.1 +0.2 +0.2 +0.3 +0.5 +0.5 +0.5 +6.0 +0.4 +0.4 HA5E +2.3 HA5PP +0.7 HA7GN +7.7 +7.5 +8.5 +8.0 HA8TKS +0.1 +0.1 +0.1 +0.1 +0.0 +0.1 +0.1 +0.1 +0.1 +0.1 HB9BXE +0.3 +0.5 +0.3 +0.3 HB9DCO -0.5 -0.7 -0.4 -0.6 -0.3 -0.4 -0.2 -0.5 -0.7 -0.3 HB9EMP -0.3 HB9GVO +0.6 +0.6 +0.5 +0.4 +0.6 +0.3 HB9YC-SDR +0.5 +0.4 +0.6 +0.3 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ZF9CW +0.4 +0.4 +0.3 +0.5 +0.7 +0.4 -0.1 -0.6 -0.5 -0.2 ZL2KS +1.5 +1.9 +1.1 +2.2 +2.3 +1.5 +1.9 +2.4 +2.4 +1.9 ZL3X -0.4 -0.6 +0.1 +0.1 -1.0 -0.0 +0.2 +0.6 ZL4YL +0.5 +0.4 +0.3 +0.2 +0.4 +0.6 +0.5 +0.7 +0.7 +0.5 ZS1NN -5.0 -3.8 -3.7 -4.2 -5.3 -3.8 -4.9 -4.5 -4.4 -4.9 Last updated 2026-06-08 00:16:31 UTC
Anchor skimmers
The below skimmers use external frequency references and are confirmed to have continuous, high accuracy. Their accuracy is also confirmed against each other on a daily basis.
DF7GB ES2RR KM3T-5 LZ3CB LZ4UX MM9PSY OE9GHV WB6BEE Last updated 2026-06-08 00:16:31 UTC
It is the owners of these skimmers who make this web page possible. Thank you.
To get good geographic coverage and a good size dataset, a two-step method is used for the analysis shown above. Since the second step also relies on spots from skimmers with slightly lower accuracy the displayed error for the anchor skimmers may not always be 0.0, even though they are perfectly accurate.
Software
The software powering this page can be found on github.