ANALISIS PERGESERAN KEDUDUKAN TITIK PADA FOTO UDARA YANG DISEBABKAN VARIASI BENTUK TOPOGRAFI DAERAH LIPUTAN

DANA APRIYANTO, Ir. Imam Abdul Roehman

1999 | Skripsi | S1 KEHUTANAN

Pemanfaatan foto udara alcan saogat membantu kegiatan pemetaan dibidang kehutanan, ha1 ini dikarenakan keunggulan-keunggulan yang dimiliki oleh foto udara lUltuk mengatasi kesulitan pengukuran langsung di lapangan. Kedudukan titik obyek yang nampak pada foto udara mengalami pergeseran dari kedudukan yang sebenamya (kedudukan peta). Pergeseran tersebut dapat dfsebabkan oleh distorsi lensa kamera, bentuk relief7topografi daerah liputan, lengkung bumi dan kemiringan sumbu kamera Untuk mencari kedudukan sebenamya dari titik-titik yang ada dalam foto udara dilakukan koreksi kedudukan titik tersebut, yang berarti menghilangkan pergeseran yang ada. Penelitian dilaksanalcan pada bulan November 1998 - Januari 1999 di RPH Redisari, BKPH Gombong Selatan, KPH Kedu Selatan. Adapun tujuan penelitian ini adalah untuk mengetahui besar pergeseran kedudukan titik dalam foto udara pada berbagai variasi bentuk topografi dan membandingkan besar pergeseran yang ditimbulkan oleh variasi bentuk topografi tersebut. Pergeseran kedudukan titik diperoleh dengan menghitung selisih jarak dan arah pasangan titik sampel sebelum dan sesudah terkoreksi dengan metode grafis triangulasi garis radial pa.da tiap strata bentuk topografi. Untuk membandingkan besar pergeseran tersebut, dilakukan uji nilai tengah berpasangan (uji-t) antar strata bentuk topo???? yang digunakan dalam penelitian ini. Hasil penelitian ini menunjukkan bahwa variasi bentuk topografi menyebabkan besar pergeseran arah yang berbeda nyata (melalui uji-t) pada taraf 5%. Bentuk topogndi landai (iereng O - 14%) menimbulkan rata-rata pergeseran arah 1. 74 °, topografi agak curmn (lereng 15-30%) menimbulkan rata-rata pergeseran 2.96°, topografi curmn (lereng 30 - 44%) menimbulkan rata-rata pergeseran 4.42° ,dan topografi terjal (lereng 45% - up) menimbulkan rata-rata pergeseran 5.88°. Disamping itu variasi bentuk topografi juga menyebabkan pergeseran jarak yang berbeda nyata (melalui uji-t) pada taraf 5% (kecuali pa.da pasangan bentuk agak curam-curam tidak berbeda nyata). Pada penelitian ini bentuk topografi landai (lereng O = 14%) menimbulkan rata-rata pocgeseran jarak 0.314 mm, topografi egak cwam (lereng 15 - 300/4) menimbulkan rata-rata pergeseran 0.396 mm, topografi curam (lereng 30 - 44%) menimbulkan rata-rata pergeseran 0.441 mm dan topografi terja1 (lereng 45% - up) menimbulkan rata-rata pergesemn 0.624 mm (PSR yang digunakan 25000).

The usefulness of an aerial photography will highly support forestry mapping activities owing to its prominences to solve difficulties of terrestrial measurement The position of a point ????mbodied by the aerial photography undergoes a displacement from its true position ( a map position). The displacement can be induced by a distortion of a camera lens, the forms of a relief or topography, the arc of the earth and the sloping position of the axis of a camera In order to get the true position of points in the aerial photography, the correction of such positional points which means to eliminate any displacement is performed. The study was undertaken from Non ember 1998 to January 1999 at RPH Re di sari, BKPH Gombong Se Iatan, KPH Kedu Selatan. The purposes of the study were to know the size of displacements of the positional points on the aerial photography in variety of topograpbycal forms and to compare the size of displacements induced by various forms of topography. The displacement of a positional point was obtained by measuring the substraction of the distance and the direction of paired sampling points before and after being con-ected with the radial-line triangulation graphical method at each stratum of topographycal forms. In order to compare the size of the displacements, the paired middle value test (t-test) between the strata of forms of the topography applied in this study. The results of the study showed that various topographical forms induced a significantly different of direction displacement (with t-test at significance level of 5%). The sloping form of the topography (with slopes of 0-14%) resulted in averaged direction displacement of 1,74° , a rather steep topography (with slopes 15-30%) resulted in averaged direction displacement of 2.96° , a steep topography (with slopes 31-44%) resulted in averaged direction displacement of 4.42° , and a very steep topography (The slopes were larger than 45%) resulted in averaged direction displacement of 5.88° . In addition, a variety of forms of topography induced a significantly different of distance displacement (with t-test at significance level of 5%), except on paired forms of rather steep-steep without significant differences. In this study, the sloping form of the topography (with slopes of 0-14%) resulted in averaged distance displacement of 0.314 mm, a rather steep topography (with slopes 15-30%) resulted in averaged distance displacement of 0.396 mm, a steep topography (with slopes 31-44%) resulted in averaged distance displacement of 0.441 mm, and a very steep topography (The slopes were larger than 45%) resulted in averaged distance displacement of0.624 mm (PSR to have been used was 25.000).

Kata Kunci : pergeseran kedudukan, kedudukan peta, bentuk topografi