Özet: Günümüzde konum belirlemede geriden kestirme yöntemi, uydu teknolojisinin gelişmesiyle pek kullanılmasa da, uyduların sinyallerinin alınamadığı yerlerde, klasik geriden kestirme yöntemini kullanmak gerekebilir. Ölçme bilgisi literatüründe geriden kestirme noktasının koordinatının hesaplanmasıyla ilgili Collins, Kaestner ve Cassini yöntemlerinde, kestirme noktasında ölçülen açıların 100g’dan küçük durumları dikkate alınmıştır. Kestirme noktasında ölçülen açılar 100g’dan büyük olduğunda geriden kestirmede hesap yöntemlerinden Collins yöntemiyle kestirme noktasının koordinat hesabında, güçlükler ortaya çıkmaktadır. Yani kestirme noktasında, bakılan nirengi noktaları arsında ölçülen açılar 100g’dan büyük olduğunda, problemin Collins yönteminin klasik haliyle çözülemeyeceği anlaşılmıştır. Problemin çözümü için literatürde bir kaynakta bu konuya yer verildiği, ancak çözümün önereceğimiz yöntemden farklı olduğu görülmüştür. Bu çalışmada, literatürdeki kaynakta belirtilen çözüm yöntemi ile tarafımızca önerilen yöntem açıklanacaktır. Çalışmada, konuyla ilgili uygulamalar yapılmış ve elde edilen bulgular ve kanaatler belirtilmiştir.
<p>In this study, we assess the accuracy of deformation rates produced from GNSS campaign measurements sampled in different frequencies. The ideal frequency of the sampling seems to be 1 measurement per month however it is usually found to be cumbersome. Alternatively the sampling was performed 3 measurements per year and time series analyses were carried out. We used the continuous GPS time series of JPL, NASA from a global network of the IGS to decimate the data down to 4 monthly synthetic GNSS campaign time series. Minimum data period was taken to be 4 years following the suggestions from the literature. Furthermore, the effect of antenna set-up errors in campaign measurements on the estimated trend was taken into account. The accuracy of deformation rates were then determined taking the site velocities from ITRF14 solution as the truth. The RMS of monthly velocities agreed pretty well with the white noise error from global studies given previously in the literature. The RMS of four monthly deformation rates for horizontal positioning were obtained to be 0.45 and 0.50 mm/yr for north and east components respectively whereas the accuracy of vertical deformation rates was found to be 1.73 mm/yr. This is slightly greater than the average level of the white noise error from a global solution previously produced, in which antenna set up errors were out of consideration. Antenna set up errors in campaign measurements modified the above error level to 0.75 and 0.70 mm/yr for the horizontal components north and east respectively whereas the accuracy of the vertical component was slightly shifted to 1.79 mm/yr.</p>
GPS campaign measurements are still in use in the monitoring of ground deformation. Campaign measurements are frequently referred to because installing permanent stations are costly, and they cannot be installed at the desired density. Using the data from the International Global Navigation Satellite Systems (GNSS) Service (IGS) permanent GPS stations, the duration, sampling interval, etc. of the campaign measurements can be simulated. Thus, the contribution of the campaign data to the monitoring of the ground deformation can be evaluated. In this study, we carried out an experiment with the aim of determining the deformation of tectonic plates at the selected IGS stations more accurately considering by extending the observation duration to a full 24 h length. We also made an attempt to take into consideration the antenna set up errors developing a scenario referring to the information available in the literature. We have decimated the continuous data of 40 globally scattered IGS stations into monthly intervals between 2012 and 2016 and estimated the deformation rates at the IGS stations from a continuous time series of four years. The continuous time series solutions for those stations were produced by the Jet Propulsion Laboratory (JPL), NASA. We compare velocities (i.e., the deformation rates) determined from GPS campaigns (in which the sampling was performed monthly and four-monthly) with those of the continuous data. The major conclusion of this study is that the vertical velocity estimation accuracy of the GPS campaign measurements had been improved by about 85% by extending the session duration to 24 h. The repetition interval of GPS campaign measurements as per one observation every four months produced only slightly coarser accuracy (i.e., on the average 8% poorer) than those of the measurements repeated once every month.
<p>The evaluation of the observation data obtained from the GPS system is performed with software. The software used today is divided into academic, web-based and commercial software. Researches generally focus on academic software and web-based services that have become widespread in recent years.Commercial software is often used by daily users, mostly in classical geodesy. These softwares differ from each other; users, their purpose of use, processing methods, accuracy, users knowledge level etc. In this study, we focused commercial software&#8217;s (Topcon Magnet version 4.0.1) accuracy of GPS positioning in single and multiple base solutions.</p> <p>10 stations included in IGS network in California, USA, one base and 2, 3 and 4 network solution results in different session times (1h to 24h) positioning accuracy was achieved. In our study, it has been found that the accuracy obtained for the horizontal components North and East varies between 2 mm and 8 mm and vertical component Up varies between 3 mm and 54 mm.</p> <p>In evaluations with a reference station distance of up to 100km, increasing the number of more than 2 reference stations (3 or 4) for horizontal compenents (North and East) did not make a significant contribution to accuracy. In the case of vertical component (Up) accuracy, it is determined that accuracy is affected by interstation distance and observation time more than the number of reference stations(1, 2, 3 or 4). it was found that it was meaningful to increase the accuracy of the vertical component to be observation time for as long as possible and reference base stations to be selected from the closest possible stations. Avoidance of short observation time (1 hour and less) for all three components was found to be important in terms of accuracy to be achieved.</p> <p><strong>Keywords:</strong> Commercial software, GPS, Multiple base solution.</p>
ÖzKırsal kesimdeki tarım arazileri arasındaki sınırlar bazen zikzaklardan oluşmaktadır. İki komşu parsel arasındaki zikzaklı sınırlar ve yakın çevresi tarımsal ürün kaybına neden olmaktadır. Bu itibarla zikzaklı sınırların düzgünleştirilmesi önem arz etmektedir. Ülkemizde arazi toplulaştırmasının yapılmadığı yerlerde zikzaklı sınırların düzgünleştirilmesi konusu, harita mühendisliğinin çalışma alanlarından biri olmaya devam etmektedir. Literatürde; komşu parseller arasındaki zikzaklı sınırların çelik şerit metre ve prizma gibi basit ölçü aletleriyle düzgünleştirilmesi hakkında bilgiye yer verilmektedir. Parsellerin köşe noktalarının koordinatları bilindiğinde, konunun kutupsal ölçmelerle çözümüne ilişkin bilgilere rastlanılmamıştır. Genellikle tarım yapılan arazilerin sınırlarında çit, tel örgü, tahta perde gibi kalıcı işaretler yer almaktadır. Sınırlardaki bu kalıcı işaretlerden dolayı, sınırların kesişme noktalarına veya sınır üzerinde belirlenen bir noktaya ölçme aletinin kurulması mümkün değildir. Zikzaklı sınırın düzgünleştirilmesinde temel prensip, yeni oluşturulan sınır nedeniyle komşu parsellerin bir alan kaybına uğramamasıdır. Bu çalışmada; sınır düzgünleştirmesi gereken komşu parsellerin köşe noktalarının koordinatları verildiğinde veya ilgili noktaların koordinatları kutupsal ölçmelerle hesaplanarak elde edildiğinde, zikzaklı sınırın, belirlenen bir istasyon noktasından kutupsal ölçmelerle nasıl düzgünleştirileceği incelenmiştir ve konuyla ilgili sayısal uygulama yapılmıştır. Çalışmanın sonucunda elde edilen bulgular ve kanaatler belirtilmiştir.
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