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Start Over Coverage 237-252

1. Characterizations of the 0-distributive semilattice

Creator:
Balasubramani, P.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
semilattice, prime ideal, and filter
Language:
English
Description:
The 0-distributive semilattice is characterized in terms of semiideals, ideals and filters. Some sufficient conditions and some necessary conditions for 0-distributivity are obtained. Counterexamples are given to prove that certain conditions are not necessary and certain conditions are not sufficient.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

2. The impact of tropospheric mapping function on PPP determination for one-month period

Creator:
Nistor, Sorin, Suba, Norbert-Szabolcs, and Buda, Aurelian-Stelian
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
geodynamika, geodynamics, PPP, mapping function, postfit residuals, standard deviation, GNSS, repeatability, 7, and 551
Language:
English
Description:
When using the PPP method, it is recommended to take into account the tropospheric influences for obtaining reliable estimates. Global Navigation Satellite System (GNSS) observations taken at low elevation suffer more strongly from atmospheric, antenna phase center variation and multipath effects, hence the observations are noisier than those at higher elevation angle, but they are essential to decorrelate the estimated station height and tropospheric zenith delay (ZTD). To relate the ZTD in the direction of an observation, the so-called mapping function (MF) are used. In this article the influence of different mapping function was studieds such as: Niell mapping function (NMF), Global Mapping Function (GMF) in conjunction with the Global Pressure and Temperature 2-GPT2, Vienna Mapping Function 1 and no mapping function. The MF were used at different elevation cutoff angles - 50 , 70, 100 and 150. The impact was analyzed: a) on the postfit residuals of the ionospheric free combination for phase (LC) and for pseudorange (PC), b) daily variability for North, East and Up component; c) evaluation of coordinates repeatability and how they are affected by the changes of the cutoff elevation angle and mapping function. The analyzed data was taken from 4 EUREF stations for a period of one month - October 2015. By using the VMF1 mapping function, the lowest value was obtained for the postfit residuals of the LC combination for all the stations. The difference in daily variation between each individual solution for the horizontal component is at the level of ~0.3 ÷ 0.5 mm, with smaller effect on the East component compared to North, whereas the Up component is at the level of ~1.0 ÷ 1.5 mm. The standard deviation (SD) is used as a measure of station position repeatability and the results suggested that for high precision determination a cutoff elevation angle of 100 should be used., Sorin Nistor, Norbert-Szabolcs Suba and Aurelian-Stelian Buda., and Obsahuje bibliografii
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public