摘要
　　數值地形模型(Digital Terrain Model，DTM)，係指不含地表植被及人工建物之地表自然起伏的數值模型。近年廣泛應用於各種領域。
　　由於台灣地區處於板塊交接處，地震頻繁，且地形陡峭河流短促，往往因颱風帶來之豐沛雨量導致土石流或坍塌，所以DTM 近年常用於坡地災害及河川淹水模式之研究。採用DTM 資料可應用於災後範圍調查，若結合現地之地質資料甚至可做到災前預警之功能，而這些均取決於DTM 之取得及精度。過去DTM　產製主要由航空攝影作業產生，其產生過程困難、取得不易，更新更是困難。而光達(Light Detection And Ranging，LiDAR)產生DTM 為目前最新的應用技術，
可取得高精度之DTM 資料，由於較不受限於天氣且由接收至處理時間快速，在防災應用上可達到近即時(Near Real Time)之目的。
　　本研究先利用內政部公告之一、二等水準點及一、二、三等衛星控制點資料來驗證LiDAR 5 公尺網格DTM、航測產製之5 公尺網格DTM 及舊有之農航所40 公尺網格DTM 之高程精度，發現LiDAR 5 公尺網格DTM 精度最高RMS 值約0.14 公尺公分、40 公尺網格DTM 之RMS 值達2.78 公尺，己不敷使用，而航測產製之5 公尺網格DTM 之RMS 值約0.59 公尺，精度雖佳，但與LiDAR相較之下，處理過程費時費力。
　　文中最後利用精度最高的LiDAR5 公尺網格DTM 結合RTK 水深測量建立烏山頭水庫之數值地形模型，使用多項式回歸方式，求出該水庫的HA、HV 曲線。再與之前的庫容數據相比，推估出目前水庫的淤積量。

ABSTRACT
　　Taiwan locates on the junction of several earth plates, which associates withfrequent earthquakes, steep landforms and short streams. Due to this kind of geology,mudflows and landslides usually come after a heavy rain brought by typhoons.Therefore, disaster protection and investigation is a big issue. Digital Terrain Model(DTM) has been applied on the researches of slope disasters and flood in the recentyears.
　　Digital Terrain Model (DTM) is a three-dimension model digitizing the naturalundulation of the earth surface, excluding vegetation and artificial buildings. It has
been applied on various areas recently. DTM could help after-disaster investigations.If cooperating with present geology information, it even could have pre-warning
functions for disasters, which depends on the precision of DTM data. In the past,DTM was created from aerial photo processing. The defects are difficulties in　obtainment of the raw data and DTM creation, even renewal. LiDAR (Light Detection　And Ranging) is the latest technology for creating DTM, which could get higher　accuracy of DTM. It has no restriction of weather and has faster proceeding from
receiving the data. Thus, it could achieve the near-real-time purpose on disaster　protections.
　　This study uses the data of the first-order leveling network, and the GPS　controlling networks announced by the Ministry of the Interior to test and verify the　vertical accuracy of LiDAR 5m grid DTM, 5m grid DTM generated by
photo-geometry and the existed 40-meter grid DTM owned by Agricultural and　Forestry Aerial Survey Institute (AFASI). The result found that the LiDAR 5 DTM　has the highest precision, and the 40-meter DTM is inadequate to use any more.　Besides, the DTM generated by photo-geometry has good accuracy, however it is　more time-consuming and more laborious compared to the LiDAR DTM.
　　In the final part, the study applies the LiDAR 5-m grid DTM, the most accurate　digital model in this research, combining with Real-Time Kinematic survey (RTK) of　water deepness to build the digital terrain model of Wushantou Reservoir. In addition,　it uses polynomial regression to get HA and HV curves of the reservoir, and then　compares with the former reservoir volume data to estimate the present amounts of　silt under the reservoir.

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