GPS data collection in 2003

Thanks to the support of the Colegio Dominicano de Ingenieros, Aquitectos, y Agrimensores (CODIA), Regional Norte, we had the opportunity to remeasure part of the 36-site GPS network that covers the Dominican Republic about one month after the September 22, 2003, earthquake. Due to the emergency nature of the post-earthquake response and to limited funding, we decided to concentrate our measurements on the northern part of the country because it was the most affected by the event. Also, preliminary coseismic deformation models indicated that significant coseismic deformation should be measurable with GPS with about a 50 km radius from the epicenter.

The measurements were carried out using 6 dual-frequency Ashtech Z-12 GPS receivers and choke-ring antennae from University of Arkansas. Power was provided by two 12 V/55 Ah car batteries and 30 W solar panels for each receiver.

The participants were divided into four teams with two sets of GPS equipment per team. All the benchmarks are located in secure locations where the equipment can be left unattended, which allowed the field work to gain in flexibility. Each site was occupied during an average of two consecutive 24 hour sessions, in a similar fashion to the 1999 and 2001 surveys (Table 4.1 and 4.2).

Field participants were:

• Team 1: Henry Turner (Univ. Arkansas), Edy Hernandez (Dominican Department of Transportation)
• Team 2: Eric Calais (Purdue University), Maria Clazadilla Ribeaux (Direccion General de Mineria)
• Team 3: Paul Mann (Univ. of Texas, Austin), Luis Pena (CODIA and private consultant)

We were able to have the equipment clear customs efficiently on Saturday, Oct. 11, thanks to the efficient help of Jose Lockhart. We purchased batteries right away and left for the field on Sunday, Oct. 12. GPS measurements took place between October 12 and 18. The three field teams returned to Santiago on Saturday, Oct., 18, were the GPS data was downloaded from the receivers and archived.

Table 4.1: Measurement schedule for the October 2003 GPS campaign in the Dominican Republic. X = full day; + = partial day, more than 12 hours of observations; - = partial day, less than 12 hours of observations.

			Su	Mo	Tu	We	Th	Fr	Sa
			12	12	14	15	16	17	18
#	FULL NAME	CODE	285	286	287	288	289	290	291
1	Monte Cristi	CRIS	-	X	X	+
2	Pepillo Salcedo	PEPE				+	X	X	-
3	Moncion	MONC		-	X	+
4	Capotillo	CAPT					+	X	-
5	Santiago	SAGO	-	X	X	+
6	Camp David	CAMP	-	X	X	+
7	La Reunion	REUN				-	X	X	+
8	Los Hidalgos	HIDA				-	X	X	+
9	Las Terranas	TERR	+	X	X	+
10	Arroyo Barril	ARRO	+	X	X	+
11	Castillo	CASX				-	X	X	+
12	La Vega	LAVE					-	X	+

Table 4.2: Measurement characteristics for the October 2003 survey

#	Site	Receiver	serial	antenna	serial	rinex	obs.
	name	type	#	type	#	height (m)	by
1	CRIS	Ashtech Z12	LP020005104	choke-ring	CR520012401	0.5000	team 1
2	PEPE	Ashtech Z12	LP020005104	choke-ring	CR520012401	0.5000	team 1
3	MONC	Ashtech Z12	LP020005103	choke-ring	CR520012404	0.5000	team 1
4	CAPT	Ashtech Z12	LP020005103	choke-ring	CR520012404	0.5000	team 1
5	SAGO	Ashtech Z12	LP020005102	choke-ring	CR520012402	0.5000	team 2
6	CAMP	Ashtech Z12	LP020005106	choke-ring	CR520012406	1.2601	team 2
7	REUN	Ashtech Z12	LP020005102	choke-ring	CR520012402	0.5000	team 2
8	HIDA	Ashtech Z12	LP020005106	choke-ring	CR520012406	1.4044	team 2
9	TERR	Ashtech Z12	LP020012202	choke-ring	CR520012403	1.5000	team 3
10	ARRO	Ashtech Z12	LP020012201	choke-ring	CR520012405	1.5000	team 3
11	CASX	Ashtech Z12	LP020012201	choke-ring	CR520012405	1.5000	team 3
12	LAVE	Ashtech Z12	LP020012202	choke-ring	CR520012403	1.5000	team 3

The field survey went well overall. The major problems encountered are listed below:

• The benchmark at site MOCA was lost as the sport arena in Moca was recently redone. We consequently remeasured LAVE instead of MOCA.
• We had problem finding the benchmark at Pepillo Salcedo and decided to measure Moncion first instead. This explains why Moncion was observed for 1 and a half day only. We were eventually able to find the benchmark at Pepillo Salcedo and observed it during the second half of the field period.

After the field work, we converted the raw GPS data into the standard RINEX format and performed a quality control. The output of the quality control is shown on Table 4.3. Multipath noise is usually on the order of 0.5 m, as expected for a site located in an open-sky environment. Site ARRO, however, systematically shows a multipath noise on the order of 1 m, as well as less than 80% of the expected amount of data collected. This is due to the growth of vegetation at the site that is partially masking the sky view.

Table 4.3: Summary of the GPS data collected during the October 2003 campaign in the Dominican Republic. First and last epoch of each file are give in year, month, day, hour:minute. Hrs = total duration of observations; dt = recording interval in seconds; #expt = maximum number of epochs; #have = number of epochs actually recorded; % = percentage of epochs recorded; mp1 = multipath noise on frequency 1 in meters; mp2 = multipath noise on frequency 2 in meters; o/slps = ratio of observations to cycle slips.

file name	first epoch	last epoch	hrs	dt	#expt	#have	%	mp1	mp2	o/slps
arro285	03 10 12 17:54	03 10 12 23:59	6.083	30	6022	4770	79	1.12	1.07	55
camp285	03 10 12 19:14	03 10 12 23:59	4.758	30	4706	4627	98	0.71	0.83	2314
cris285	03 10 12 20:15	03 10 12 23:59	3.742	30	3783	3745	99	0.46	0.47	3745
sago285	03 10 12 17:09	03 10 12 23:59	6.833	30	6853	6846	100	0.46	0.49	6846
terr285	03 10 12 22:06	03 10 12 23:59	1.883	30	1783	1644	92	0.53	0.54	548
arro286	03 10 13 00:00	03 10 13 23:59	23.98	30	22474	17311	77	1.12	1.06	50
camp286	03 10 13 00:00	03 10 13 23:59	23.98	30	22376	20850	93	0.83	0.93	596
capt286	03 10 13 14:30	03 10 13 23:59	9.492	30	9313	9227	99	0.48	0.50	1538
cris286	03 10 13 00:00	03 10 13 23:59	23.98	30	22315	22246	100	0.45	0.47	22246
sago286	03 10 13 00:00	03 10 13 23:59	23.98	30	22385	22303	100	0.45	0.47	7434
terr286	03 10 13 00:00	03 10 13 23:59	23.98	30	22459	20786	93	0.52	0.53	139
arro287	03 10 14 00:00	03 10 14 23:59	23.98	30	22474	17409	77	1.18	1.07	54
camp287	03 10 14 00:00	03 10 14 23:59	23.98	30	22378	21068	94	0.83	0.89	752
capt287	03 10 14 00:00	03 10 14 23:59	23.98	30	22359	22257	100	0.47	0.50	11129
cris287	03 10 14 00:00	03 10 14 12:46	13.66	30	11562	11521	100	0.43	0.45	11521
sago287	03 10 14 00:00	03 10 14 23:59	23.98	30	22380	22317	100	0.46	0.47	5579
terr287	03 10 14 00:00	03 10 14 23:59	23.98	30	22463	20798	93	0.53	0.53	212
arro288	03 10 15 00:00	03 10 15 14:29	14.48	30	13977	10598	76	1.07	1.09	48
camp288	03 10 15 00:00	03 10 15 14:36	14.60	30	14069	12394	88	1.04	1.10	590
capt288	03 10 15 00:00	03 10 15 18:08	18.13	30	17453	17348	99	0.46	0.47	17348
casx288	03 10 15 17:11	03 10 15 23:59	6.800	30	6801	6341	93	0.54	0.55	115
cris288	03 10 15 00:00	03 10 15 12:10	12.16	30	11682	11627	100	0.44	0.46	11627
hida288	03 10 15 20:02	03 10 15 23:59	3.958	30	4009	3857	96	0.58	0.58	3857
monc288	03 10 15 22:16	03 10 15 23:59	1.717	30	1710	1664	97	0.49	0.50	1664
pepe288	03 10 15 14:58	03 10 15 23:59	9.025	30	8848	8111	92	0.61	0.66	737
reun288	03 10 15 00:00	03 10 15 23:59	23.98	30	15074	12263	81	0.45	0.49	943
sago288	03 10 15 00:00	03 10 15 17:10	17.16	30	16545	12729	77	0.44	0.47	2546
terr288	03 10 15 00:00	03 10 15 12:31	12.52	30	12062	11186	93	0.52	0.53	143
casx289	03 10 16 00:00	03 10 16 23:59	23.98	30	23441	22402	96	0.55	0.56	200
hida289	03 10 16 00:00	03 10 16 23:59	23.98	30	23365	22800	98	0.59	0.58	5700
lave289	03 10 16 18:17	03 10 16 23:59	5.700	30	5813	5763	99	0.48	0.49	1153
monc289	03 10 16 00:00	03 10 16 23:59	23.98	30	23398	22866	98	0.50	0.51	4573
pepe289	03 10 16 00:00	03 10 16 23:59	23.98	30	23349	21474	92	0.63	0.63	859
reun289	03 10 16 00:00	03 10 16 23:59	23.98	30	23370	23291	100	0.44	0.47	23291
casx290	03 10 17 00:00	03 10 17 23:59	23.98	30	23448	22329	95	0.56	0.58	147
hida290	03 10 17 00:00	03 10 17 23:59	23.98	30	23362	22698	97	0.58	0.59	2522
lave290	03 10 17 00:00	03 10 17 23:59	23.98	30	23424	23193	99	0.47	0.49	928
monc290	03 10 17 00:00	03 10 17 23:59	23.98	30	23396	22796	97	0.50	0.51	3799
pepe290	03 10 17 00:00	03 10 17 23:59	23.98	30	23345	21631	93	0.63	0.65	983
reun290	03 10 17 00:00	03 10 17 09:47	9.775	30	9042	8953	99	0.40	0.43	4477
casx291	03 10 18 00:00	03 10 18 14:32	14.53	30	14055	13620	97	0.54	0.56	568
lave291	03 10 18 00:00	03 10 18 16:21	16.34	30	15784	15674	99	0.46	0.46	2239
monc291	03 10 18 00:00	03 10 18 14:45	14.75	30	14291	13984	98	0.47	0.49	6992
pepe291	03 10 18 00:00	03 10 18 12:37	12.62	30	12196	11328	93	0.62	0.63	1133

In addition to our campaign measurements, we were able to use continuous GPS data from 4 sites operated by the Dominican Department of Justice. These sites are located at Barahona, San Pedro de Macoris, La Vega, and Santiago Rodriguez.