Presizyonlu elektromanyetik uzunluk ölçmelerinde atmosferik etkilerinin ve ölçek hatalarının lokal ölçek parametreleri modeli ile giderilmesi
Başlık çevirisi mevcut değil.
- Tez No: 55922
- Danışmanlar: PROF.DR. RASİM DENİZ
- Tez Türü: Doktora
- Konular: Jeodezi ve Fotogrametri, Geodesy and Photogrammetry
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1996
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 101
Özet
ÖZET Günümüzde, yüksek teknoloji ürünü elektronik uzunluk ölçerlerle uzunluk ölçmeleri, jeodezik çalışmaların vazgeçilemez uygulaması olmuştur. Jeodezik çalışmalarda, milimetre mertebelerinde yüksek doğrulukların planlanması ve beklenmesi, ölçmelerde kullanılan aletlerin ölçme doğrulukları ile birlikte diğer değerlendirmelerin de iyileştirilmesini zorunlu hale getirmiştir. Bu amaçla gerçekleştirilen çalışmaların büyük bir kısmı, atmosferik etkilerin presizyonlu olarak belirlenmesi ve ölçülerin bu etkilerden arındırılmasına yönelmiştir. Bu çalışmada, öncelikle elektromanyetik uzunluk ölçmelerinin güncel temel fiziksel eşitlikleri özetlenmiştir. Atmosferik parametrelerin presizyonlu olarak ölçülmesi için geliştirilen sistemler ve ölçme yöntemleri tanımlanmıştır. Atmosferin ölçme dalgalarına olan etkileri incelenmiş, bu etkilerin belirlenmesi ve ölçülerden kaldırılması için geliştirilen atmosferik modeller, çevresel ve bütüncül modeller olarak özetlenmiştir. Mikrometeoroloji alanındaki gelişmelere paralel olarak geliştirilen türbülans transfer ve kenar oranları modellerinin birlikte ele alınmasıyla elde edilen lokal ölçek parametreleri atmosferik modelinin teorik esasları verilmiştir. Lokal ölçek parametreleri modeli, bir mikrojeodezik test ağında Kern Mekometer ME 5000 ile gerçekleştirilmiş beş yıllık presizyonlu kenar ölçülerine uygulanmıştır. Model sonuçlan; gerek ağ dengelenmesinde ve gerekse deformasyon analizinde kullanılarak test edilmiş ve irdelenmiştir. Lokal ölçek parametreleri (LÖP) modelinin söz konusu test ağında, ölçülerin değerlendirilmesinde kullanılan lineer kırılma indisi modeline göre, tüm periyotlarda, ağ dengelemesinde ve deformasyon analizinde daha presizyonlu sonuçlar verdiği gösterilmiştir. Sonuç olarak, lokal ölçek parametreleri modeli, yüksek doğruluk gerektiren tüm uygulamalarda atmosferik düzeltmelerin hesaplanmasında kullanılabilir bir metoddur. Metod, ayrıca aletsel ölçek değişimlerinin etkisini de ortadan kaldırarak, ağda ölçek homojenleştirmesi sağlamaktadır. Bu durum, deformasyon analizini kolaylaştırmaktadır. Lokal ölçek parametreleri metodu, ölçme robotları ile yapılan ölçülerin değerlendirilmesinde de diğer yöntemlere göre daha iyi sonuç veren bir yöntem olarak önerilmektedir. XV
Özet (Çeviri)
SUMMARY AN INVESTIGATION TO REMOVE ATMOSPHERIC EFFECTS AND SCALE ERRORS USING A LOCAL SCALE PARAMETER MODEL IN PRECISE EDM MEASUREMENTS The main limitation of the attainable accuracy in electronic distance measurement (EDM) is the determination of the representative refractive index along the measured wave path, in principle, electronic distance measurements should be corrected for the integral refractive index over the entire wave path. This could involve the measurement of temperature, pressure and humidity along the wave path to calculate the refractive index and the subsequent integration of these refractive index values along the wave path. In practice, simplified methods called“peripheral atmospheric models”based on 'end point 'measurements' are usually adopted. Refractive indices evaluated from temperature, pressure and humidity readings taken at instrument height at the end points of lines will represent the integral value over the wave path as long as the EDM wave path is parallel to the ground. This case occurs most likely on close range where lines of more than a few hundred metre lengths, the average ground clearance is likely to exceed significantly instrument and reflector heights. In these cases, the refractive indices computed from meteorological observations at the terminals will no longer closely approach the integral value over the wave path. Diurnal temperature variations in the lowest 1 00 metres of the atmosphere on clear (sunny) summer days show that temperatures measured at instrument height are not representative for temperatures at a height of, say, 100 m above ground. Temperatures measured during day light hours are too high and those measured at night too low when compared with temperatures at 100 m. It can be shown that first velocity corrections based on end point measurements could make the distances 4 ppm too short at midnight and 2 ppm too long at noon. It should be noted that these errors apply to clear nights and sunny days as define above. The magnitude of these effects will be considerably reduced for similar lines on heavily overcast and windy days. Refractive indices computed from measurements of atmospheric parameters at the terminals of lines can severely bias the corrected distances. The ground proximity effects are worst on clear sunny days and in clear nights. Generally speaking, cloud cover over EDM lines and/or moderate to strong winds will reduce the ground proximity effects on meteorological end point measurements. As it is not practical to restrict EDM observations to those favourable conditions, techniques have been XVIdeveloped which overcome some of the limitations of the end point measurements of atmospheric parameters. Very powerful method developed to overcome these limitations is previously known as“length ratios”. This method not only reduces scale biases in the distance ratios due to atmospheric effects, meteorological measurement errors and network constrains but also saves time by omitting the measurements of some atmospheric parameters. The length ratio method is a so-called“operational”model and makes use of the fact that all distance measurements made from one station to a number of reflector stations in a short time interval exhibit proportional atmospheric propagation effects. Originally, the ratio of line pairs was formed and introduced as observations into the least squares adjustment. However, it is of advantage to use the technique in the form of a“local scale parameter model”where all distances or groups of distances measured from one station are assigned a common but unknown scale parameter. When compared with the ratio method of line pairs, the network adjustment exhibits a much improved degree of freedom. This new technique is classified under the term of integral atmospheric model due to its theory tha* is based on estimating the integral atmospheric values along the wave path.' The local scale parameter model needs only atmospheric parameter measurements at instrument station. The main aim of this study is to derive all details of an improved local scale parameter (LSP) model for electro-optical distance measurement from first principles and show how the method can be applied using the standard least squares analysis technique. Moreover, the LSP model is applied for the EDM measurements obtained from five epochs of observations made with a Mekometer ME 5000 precise EDM instrument in a geodetic test network which has been established for earthquake prediction research on the North Anatolian Fault Zone, Mudurnu. To show how powerful the LSP model is, same data groups are also processed using a peripheral atmospheric model which is being the best performed peripheral model in this geodetic network. The best performed peripheral model is based on conventional first velocity correction using Owen's formulae and determined as the best model after a research carried out in this test network using different peripheral atmospheric models with same data groups. In this study, the basic principles of electro magnetic distance measurements are discussed and some equations are redefined from the first principles. Since one of the most important steps in atmospheric modelling is to measurements of the atmospheric parameters, types of atmospheric parameter measurements, instruments and some instructions are mentioned. Different kinds of atmospheric parameter measurement techniques are shown by means of some photos taken during the real field works in the test network. The geodetic test network is defined and research activities executed since its established time are discussed. Most commonly used peripheral atmospheric models to overcome the limitations due to atmospheric effects, Linear Refractive Index Model (standard first velocity correction using Owen's formulae), Turbulent Transfer Model, Logarithmic XVIIRefractive Index Model, Spherical-Parabolic Refractive Index Model, Length Ratio Methods and Simplified Local Scale Parameter Model are given under the term of peripheral atmospheric models. All mentioned peripheral atmospheric models are taking care of first and second velocity corrections on the basis of some assumptions. The local scale parameter model is not only taking first and second velocity corrections into account also counting the vertical potential temperature gradient and temperature and pressure changes along the wave path. Also LSP model introduces the (nref -£,) term into a least square adjustment as an unknown and solves this term as a scale parameter. This term basically refers the first velocity correction. The basic form of local scale parameter model is defined as follows;,dB AS = - (iA S + CAS mm + CApS mm+ - (a pCAS sin z): öh 24 The first term of the formula is being the local scale factor introduced into the least square adjustment: The second term' is taking the vertical' potential temperature gradient into account along the wave path as well as the third term temperature and pressure changes. Fourth term is basically presenting the second velocity correction. As the application of the study, LSP model is applied for the EDM measurements obtained from five epochs of observations made with a Mekometer ME 5000 precise EDM instrument in a geodetic test network which has been established for earthquake prediction research on the North Anatolian Fault Zone, Mudurnu. Same data groups are also processed using the best performed peripheral atmospheric model, linear refractive index model. Processing same data groups using two different methods makes us enable to decide which model works best. For the aim of deciding about the best model some criterion are applied on the results. The basic comparisons are made using the least square adjustment results. These results are summarised as below, Table 1 Positioning errors and internal precisions of the measured distances obtained with Local scale parameter model XVIIITable 2 Positioning errors and internal precisions of the measured distances obtained with Lineer refractive index model As it is seen in the Tables 1 and 2, the local scale parameter model performs very well. The results obtained from five epochs are evident that LSP model is very powerful. Since all results over five years of period consistent with each other, it can be said that these are free of random effects. The LSP solution of a geodetic network gives us a minimum constraint least squares solution due to the absolute scale of the distances is lost as no absolute first velocity corrections are applied. It shouldbe noted that the coordinates of the network with minimum constraints are free of any scale distortions. This is very important for deformation surveys. Because of this advantage of LSP model application, further post processing is made to understand the behaviour of the LSP model in terms of deformation analysis. Using same five epochs of observations processed with local scale parameter model and linear refractive index model, a deformation analysis is made between epochs. In the test to determine reference control point block (stable control points for the analysis), two different result obtained from two different models. Basically, the linear refractive index model is not good enough to determine movements between the epochs. Taking the reference control points stable determined with LSP results, a deformation analysis is processed with two different data sets. After the analysis, a strange trend is seen with LSP processed data set as far as the movements are concerned. This found trend defined by geologists at the time of first project started in the area that indicates the assumed earthquake fault zone. Using other atmospheric correction models would not be certainly good enough to determine such results. The following figure indicates the atmospheric corrections in ppm obtained from two different processes. The reference lines in the figure are selected according to their length which are presenting the different profiles and lengths in the network. As it is seen in the Figure 1, using a peripheral atmospheric model leads to over correct the measured distances as far as the atmospheric effects are concerned. XIX50 45-1 40- 35- I 30i i **? o E 2
Benzer Tezler
- Presizyonlu hidrografik ölçmelerde bat-çık etkisinin GPS yöntemi ile belirlenmesi
Başlık çevirisi yok
REHA METİN ALKAN
Doktora
Türkçe
1998
Jeodezi ve Fotogrametriİstanbul Teknik ÜniversitesiJeodezi ve Coğrafi Bilgi Sistemleri Ana Bilim Dalı
PROF. DR. EMİRHAN ALGÜL
- Presizyonlu nivelman ağlarında dengeleme öncesi stokastik model için bir yaklaşım
A Study for stocastic model before adjustment in precise levelling
YUNUS KALKAN
- Presizyonlu elektro magnetik kenar ölçmelerinde atmosferik model araştırması
Study on the investigation of the atmospheric effects on electro magnetic distance measurements in a geodetic network
MEHMET GÖKALP ALANKO
- Presizyonlu nivelman yerine trigonometrik nivelman yönteminin kullanılabilirliği üzerine bir çalışma
Comparison of precise levelling and trigonometric height determination methods
AYHAN CEYLAN
Doktora
Türkçe
1993
Jeodezi ve FotogrametriSelçuk ÜniversitesiJeodezi ve Fotogrametri Ana Bilim Dalı
PROF.DR. ORHAN BAYKAL
- Presizyonlu eğim sensörüyle büyük yapıların deformasyonlarının izlenmesi
Monitoring deformations of large buildings by precision inclanation sensors
BİHTER ÖZÖNER
Yüksek Lisans
Türkçe
2000
Jeodezi ve Fotogrametriİstanbul Teknik ÜniversitesiDOÇ.DR. RAHMİ NURHAN ÇELİK