Site positions, October survey

The first results of the October 2003 GPS survey are precise coordinates for each of the sites observed (Table 6.1). We find 1-$\sigma$ uncertainties on the order of 2.5 mm for the east component, 1.5 mm for the north component, and 8 mm for the vertical component. These uncertainties are typical for high accuracy GPS surveys. Site Arroyo Barril is obviously an outlier, with uncertainties twice higher than the average. This is probably due to the presence of high vegetation surrounding the site, as also indicated by the multipath noise analysis (Table 4.3). Similarly, the sky view at site Los Hidalgos is partially blocked by a palm tree, which may explain its slightly higher vertical uncertainty than average. We have no explanation at this point for the higher uncertainty than average at site La Reunion, located near the runway at the Puerto Plata airport, with no sky obstruction.

Table 6.1: Precise site coordinates derived from the 2003 GPS survey in the Dominican Republic, given at Epoch 2003.7959 in ITRF2000.

Long.	Lat.	sE	sN	sH	SITE	X	Y	Z
(deg)	(deg)	(mm)	(mm)	(mm)		(m)	(m)	(m)
290.694	18.461	2.2	1.3	5.5	SPED	2138652.2794	-5661444.6748	2006842.5876
290.552	19.202	5.3	2.5	17.8	ARRO	2115235.3782	-5641970.8678	2084416.2784
290.499	19.321	2.4	1.5	7.6	TERR	2108555.7487	-5639798.9738	2096932.9624
289.469	19.223	2.1	1.3	5.9	LVEG	2008034.7251	-5680307.7033	2086669.6127
289.435	19.759	2.7	1.8	10.8	REUN	1998096.2559	-5662708.8963	2142559.9793
289.434	19.300	2.4	1.5	8.0	LAVE	2003704.9784	-5679149.9413	2094803.0877
289.364	19.512	2.4	1.6	8.4	CAMP	1994213.6121	-5674345.7739	2117050.4612
289.307	19.467	2.4	1.5	8.0	SAGO	1989025.2458	-5677582.0766	2112172.5920
288.971	19.739	2.6	1.8	10.1	HIDA	1952394.4482	-5679572.7001	2140575.6258
288.902	18.209	2.2	1.3	5.9	BAR_	1963355.5612	-5733913.7922	1980342.0131
288.852	19.410	2.3	1.5	8.1	MONC	1944640.0175	-5695338.0936	2106312.0443
288.659	19.475	2.1	1.3	6.3	SROD	1924568.6665	-5699372.3536	2113052.4232
288.350	19.845	2.4	1.4	7.1	CRIS	1889421.6581	-5696534.4596	2151530.3726
288.329	19.420	2.3	1.5	7.3	CAPT	1892435.2093	-5712356.3996	2107304.5653
288.245	19.703	2.4	1.6	8.9	PEPE	1880631.8245	-5705001.2580	2136735.5325
289.972	19.211	2.5	1.6	8.6	CASX	2057942.2223	-5662856.6829	2085388.5903

An additional way of estimating the measurement precision consists in computing the residual mean square (RMS) of the daily scatter of the positions about their mean value. This quantity is usually called ``daily repeatability''. The campaign sites were observed for too short a time period to provide meaningful statistics. However, the Dominican continuous GPS sites have provided data for 7 days, allowing us to estimate repeatabilities (Table 6.2). We find repeatabilities on the order of 2 mm, 3 mm, and 7 mm for the NS, EW, and vertical components, respectively. These repeatabilities are consistent with the uncertainties reported above. Figure 6.1 shows the corresponding position time series, illustrating the fairly small daily scatter.

Table 6.2: Repeatabilities (i.e., RMS of the daily scatter of the positions about their mean value for the 4 continuous GPS sites operating in the Dominican Republic for the period of the October 2003 survey.

SITE	NS (mm)	EW (mm)	UP (mm)
SROD	2.0	2.0	5.0
BAR_	3.0	1.0	9.9
SPED	2.0	3.0	4.0
LVEG	2.0	5.0	6.0

Figure 6.1: Position time series for the 4 continuous GPS sites operating in the Dominican Republic. Each point represents a position derived from a 24-hour solution, with an error bar representing its formal uncertainty. Top panels: NS component; middle panels: EW component; bottom panels: vertical component.