例句與造句

1. In this paper , the main research works are as follows : 1 ) survey and analysis previous work in auv navigation and summarize : as the cumulate error , the dead - reckoning and inertial navigation systems ca n ' t be used without other modified system ; the acoustic navigation system is used only in small range , and is very expensive . 2 ) two important approaches in geophysical navigation techniques are summarized , one is terrain contour based navigation , this approach is investigated keystone today ; the other is image based navigation , due to no perfect image sensors and image seabed map , this approach has seldom been practised . 3 ) two important terrain contour based navigation algorithms has been applied to auv , one is match algorithm - based terrain contour match ( tercom ) ; the other is kalman filter - based sandia inertia terrain - aided navigation ( sitan )
   主要研究?jī)?nèi)容包括：一、總結(jié)分析了當(dāng)前水下導(dǎo)航的常用方法和不足之處，指出基于航位推算的導(dǎo)航方法，存在著最大的問(wèn)題就是導(dǎo)航誤差的積累問(wèn)題，如果沒(méi)有修正系統(tǒng)，這種方法很難滿足使用要求；其次指出基于聲學(xué)的導(dǎo)航方法，造價(jià)昂貴，導(dǎo)航范圍有限，難以滿足自主水下航行器大范圍導(dǎo)航的需求；二、總結(jié)了當(dāng)前水下地形輔助導(dǎo)航的主要技術(shù)路線，一是基于地形高程的匹配方法，這是當(dāng)前研究的重點(diǎn)；二是基于地形圖像的匹配方法，由于缺乏良好的圖像傳感器，和可用的海底圖像地圖，目前這種方法還有待研究發(fā)展；三、將兩種地形高程匹配的常用方法應(yīng)用到自主水下航行器上：以相關(guān)算法為前提的地形輪廓匹配( tercom )方法和以卡爾曼濾波為基礎(chǔ)的桑迪亞慣性地形輔助導(dǎo)航( sitan )方法，前者算法簡(jiǎn)單可靠，但是導(dǎo)航精度不高，后者雖然精度比較高，但存在著算法較為復(fù)雜、有可能發(fā)散和出現(xiàn)奇異值等問(wèn)題。
2. It's difficult to find seabed mapping in a sentence. 用seabed mapping造句挺難的