Below the statistics of ZTD estimates from all AC's are compared to HIRLAM analysis times 00, 06, 12 and 18 UTC. GPS ZTD observations are linearly interpolated to these times.

Period	2012/05/14 - 2012/05/22

AC	Total number of Obs.	Number of Sites	site biases mean/stddev	site stddev mean/stddev	stddev. of all Obs.
ASIC	7985	171	12.1 / 46.8	21.0 / 34.7	52.8
ASI_	2895	61	3.5 / 12.0	17.6 / 5.6	22.1
BKG_	4490	91	17.5 / 31.2	25.7 / 45.3	64.1
GFZ_	14576	293	14.8 / 15.6	13.7 / 22.2	32.5
GOP1	3102	62	14.8 / 28.2	25.6 / 43.8	60.4
GOPG	1049	25	81.2 / 197.0	23.5 / 36.5	137.1
G_UK	962	25	82.2 / 196.2	22.8 / 35.2	134.5
IGE_	7008	195	5.1 / 37.4	10.9 / 4.4	15.7
KNM3	3030	63	13.5 / 24.7	18.2 / 35.6	50.3
KNM4	1527	33	10.1 / 21.1	18.1 / 37.2	49.7
LPTR	2189	46	-4.4 / 7.4	16.1 / 21.3	28.8
LPT_	5169	114	14.8 / 51.5	16.2 / 29.5	46.9
METO	10455	219	5.4 / 16.4	14.9 / 24.4	34.2
NGAA	15415	370	-37.0 / 245.4	23.8 / 58.3	223.7
N_UK	94	2	0.0 / 0.0	0.0 / 0.0	0.0
ROB_	7881	166	9.5 / 25.7	21.3 / 34.7	48.1
SGN1	12770	339	-0.8 / 20.8	19.5 / 25.8	41.0
SGNC	24	2	747.6 / 3.5	12.1 / 0.5	745.1
SGN_	12436	312	-1.1 / 21.7	19.8 / 26.8	41.4