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Hidrografide prezisyonlu derinlik belirlemesi için akustik iskandil ölçülerine getirilecek düzeltme ve indirgemelerin incelenmesi

Başlık çevirisi mevcut değil.

  1. Tez No: 75481
  2. Yazar: DENİZ BAŞ
  3. Danışmanlar: PROF. DR. EMİRHAN ALGÜL
  4. Tez Türü: Yüksek Lisans
  5. Konular: Jeodezi ve Fotogrametri, Geodesy and Photogrammetry
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1998
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Jeodezi ve Fotogrametri Mühendisliği Ana Bilim Dalı
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 84

Özet

ÖZET Hidrografi, yaklaşık %70 i sularla örtülü yeryüzünün, sualtı topografyasının belirlenmesi amacıyla geliştirilmiş bir bilim dalıdır. Hidrografinin uygulama alanı, amaca uygun deniz, göl ve akarsu haritalarının yapılması, su ortamında yapılacak her türlü aplikasyon işleri, ortalama su seviyesinin belirlenmesi, yer çekimi ivmesi (gravite) ölçmelerinin yapılması olarak sayılabilir. Beslenme, maden ve enerji kaynakları yönünden son derece önem kazanan denizlerde, gerek petrol, doğal gaz ve maden kaynaklarının araştırılması, gerekse güvenlik amaçlı çalışmalarda sualtı topografyasının belirlenmesi zorunlu olmaktadır. Kaynakların kullanılmasına yönelik üretilecek her türlü projede, derinlikleri belirlenmiş hidrografi haritalarının temel altlık görevi üstleneceği kesindir. Bu hidrografi haritalarında işaretlenmiş derinlikler ve eş derinlik eğinlerinin doğruluğu, kullanılan yöntemlerle de ilişkilidir. Kullanılan yöntemler ne kadar presizyonlu olursa, hidrografık haritaların altlık olarak alındığı projeler o derece güvenilir olacaktır. Projelerin uygulamalarında kullanılan altlıkların doğruluğu arttıkça, proje maliyetlerinden ve zamandan kazanç sağlanacaktır. Çünkü hata içeren hidrografi haritaları ile yapılacak uygulamalarda, değişik ve ciddi problemler ortaya çıkacak, bu problemlerin çözümü için, ölçme ve hesapların tekrar yapılması gerekebilecektir. Deniz, göl gibi doğal sınırlara sahip komşu ülkeler arasında deniz yetki alanlarının, münhasıran ekonomik bölgenin ve kıta sahanlıklarının belirlenmesinde derinliklerin doğruluğu son derece önemlidir. Teknolojik gelişmelere paralel olarak, önemi giderek artan hidrografîk çalışmalarda, derinlikler santimetre doğruluğunda belirlenebilmektedir. Bu çalışmada derinlik ölçme yöntemleri kısaca açıklandıktan sonra, tez konusunu oluşturan Akustik İskandil Yöntemi ve ölçülere getirilecek düzeltme ve indirgemeler ayrıntılı olarak incelenmiştir. Ölçme hataları ayrıntılı olarak açıklanarak, bu hataların etkilerinin azaltılması için alınabilecek önlemler belirtilmeye çalışılmıştır. IX

Özet (Çeviri)

SUMMARY THE ANALYSIS OF THE CORRECTIONS AND THE REDUCTIONS ON ACOUSTIC MEASUREMENTS FOR PRECISION DEPTH DETERMINATION EV HYDROGRAPHY Hydrography is a branch of science dealing with the topographical status of water covered places which form 70% of the Earth. Cartography of seas, lakes and running waters; determining the average water-level; the survey of gravity acceleration form the fundamentals of hydrography. The importance of hydrography has increased with the emergence of the fact that seas are as rich as lands in dietetical, mineralogical and row materials for energy point of view and that shipping is more economical. Besides, hydrographic charting has been essential for underwater and nearwater technical service planning and works in a modern way. Hydrographical measurements targeting this aim has usually been made in shallow seas, shallow seas, shoals, lakes, rivers, dams, harbours, etc. In order to determine the topographical status of waterbase, vertical measurements towards the surface of the water are made. This process is called 'sounding', and the point of which depth is identified is called 'sounding point'. Depth measurements are generally named according to the instrument used. Measurements are made either by an operator or automatically by the instrument. Measuring post consist of two people whatever the method is. Depth values are acquired either directly or indirectly. The point of which the depth measurement made and the depth value- as well as the time of measurement- are recorded on the measurement list or automatically into a magnetic medium. Depth measurements are classified according to the values acquired. These are: 1. Directly resulting methods 2. Indirectly resulting methods. In directly resulting methods, depth values are read directly during the measuring process. These methods are named according to the instruments used: l.Lath Measurement 2.Rope Measurement 3. Mechanical MeasurementThey are divided into four according to the physical rules applied in the indirectly resulting methods: 1. Hydrostatic Measurement 2.Thermometric Measurement 3. Laser Measurement 4.Acoustic Measurement Directly and indirectly resulting methods have briefly been explained in this study. Acoustic measurement method and corrections and reductions on measurements are studied in detail Acoustic measurement method is based on the evaluation of the reflections of acoustic waves from the reflections of acoustic waves from the reflectors underwater. The measurement (of the topographical profile under the hydrography vehicle moving on a line) according to the principles of acoustic wave diffusion form the fundamentals of the method. Acoustic measurement is a depth measuring method safely used for it minimises individual errors, unaffected by streams and for its high efficiency. Sound impulses -vertically sent from the transducer in water towards the waterbase- spread in a conic manner and are reflected back to the receiving unit. The spread velocity of sound waves in water change relating to the density of water, that is, heat, salinity and depth. If the velocity is known, cruising time can be calculated with the below equation: The general equation used for calculating the spread velocity of sound waves in water is as follows: VA = Vo +A Vp + A Vc + A VT + A VOTp And the meaning of the symbols used in the equation are stated below Vo : The spread velocity of sound in water under normal conditions, that is, 1445,5 m/s according to S.Kuwahara, 1449,2 m/s according to W.D.Wilson AVP : pressure correction AV0 : salinity correction AVT : heat correction AVorp : the correction in case of a simultaneous change of the data. Acoustic measuring instruments consist of 3 units. These units can be classified as: XI1. Transducer 2. Ekograf 3. Energy unit Sound impulses reflected from the waterbase back to the receiving unit are chronologically registered in the record-list. The earliest arriving sound impulse is revealed as the top depth value. The latter thicken the line and cause it droop. Depths are read from the top edge of the graphic except for special cases. Yet, evaluations are made differently according to he shape of the base (steep or plain). Temporary water depth is called H 'row data'. The following corrections are made width the 'row data :. Velocity correction (dHv). Transducer depth correction (a). Slope correction (dHe). Settlement and squat correction. Datum and tide correction Owing to this difference all depth measurements must be velocity-corrected. It is advised that the control unit should be calibratable according to the average sound velocity determined for the medium since it would be time-consuming to velocity- correct the depth measurements. The temporary row depth read from the record list reveals the depth from the waterbase to the transducer and represented as: H' = fV-t If the distance between the transducer and the water level is added to the this depth, temporary depth for the sounding point will be calculated with H = H' + a In practise, this correction may be disappeared by changing the zero point in record lists as much as the transducer depth. Therefore, the depth value in the record lists will be equal to the H. Transducer depth correction is a result of transducer's being in water. Since the sound impulses which travels the shortest route will be received the earliest, always values smaller than the real depth are measured in acoustic measurement. In this study, slope correction, which is of great importance for precision depth determination, is analysed under two main titles: when the echo sounder units are in different places. Within these two titles are the slope correction formulae: xu. According to the real slope. According to the apparent slope After the corrections, depth measurements are reduced to the surface which correspond to the average water level determined by marigraphic measurements. Reasons of errors in acoustic measurement can be classified in three main titles. These are :. Water caused errors. Instrumental errors. Individual errors Precisions of positions of sounding points are as important as depth measures precision in Hydrography. Therefore, positioning errors should be known first. Factors affecting position precision at sea can be indicated as follows:. Measuring method. Quality of measuring instruments. Experience of the operators. Specifications of the research ship. Positions and precisions of terrestrial points. Evaluation style of measurement. Effects of the medium A 10-100 meter position correction which is sufficient in oceans can be raised to 1 meter in coastal or harbour works and underwater pipe or cable installations, expected positioning instruments. As for applications, expected positioning precision can be defined as 3-5 m. for territorial waters and offshore works. Positioning correction has been reduced to 10 m for moving targets, and 1 m for still targets with GPS (Global Positioning System). As a result, it is quite obvious that the precision acquired in terrestrial positioning with modern systems is higher than depth measuring precisions owing to nautical conditions. An Ha corrected depth value is gained after the application of corrections which were explained on an H1 depth, measured by an acoustic depth measuring instrument. Therefore, Hd depth is calculated as follows in acoustic measurement: xmH,=H' + a + dH +dH +dH +. d v e a and the precision of the depth is: 'h^V* mH =± ^m2H' +m2a +m2Hv +m2H“ +m2H”+.. In this formula; mH, : KM.S.(Root Mean Square) of row depth measures m : KM. S of transducer depth. mu : KM. S of velocity correction. riv m^ : KM. S of slope correction. tie m., : KM. S of calibration correction of the instrument. Ma In modern acoustic measuring instruments depth precision per 100 m mH' = ± 0.10 - 0.20 m. Velocity correction precision per 100 m is mu = ± 0.30 - 0.60 m, and depth riv determination precision is moK = ± 0.5 mm M (vertical scale). Transducer depth measuring precision can be assumed as ma = ± 0.05 m on an average. Since calibration correction is done by rope or mechanical measurement, it is assumed that m" ^ hiok. Slope correction precision is primarily related to the slope of waterbase. Under these conditions, general precision of the method can be assumed as follows: In classical instruments : ± 1 m (±%1 H) In precision instruments : ± % (0. 1 - 0.25)-H xiv

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