LiDAR(Light Detection and Ranging)

這讓我想起在2008年交通大學史天元教授在東沙群島執行水透光達實驗，利用機載雷達探測海底地形的實驗。

pulses of light travel to the ground. They return and are detected by the sensor giving therange (a variable distance) to the Earth. This is how LiDAR earned its name – Light Detection and Ranging.

看似簡單原理，卻有許多技術必須突破，包含多次的反射、雷達光速強度、反射點的分類等等。

 

 

 

 

 

LiDAR data is a rare, precious GIS resource

From ground to air, explore the types of LiDAR systems

1. Profiling LiDAR was the first type of Light Detection and Ranging used in the 1980s for single line features such as power lines. Profiling LiDAR sends out an individual pulse in one line. It measures height along a single transect with a fixed Nadir angle.

2. Small Footprint LiDAR is what we use today. Small-footprint LiDAR scans at about 20 degrees moving backwards and forwards (scan angle). If it goes beyond 20 degrees, the LiDAR instrument may start seeing the sides of trees instead of straight down.

Two types of LIDAR are topographic and bathymetric:
i. Topographic LIDAR maps the land typically using near-infrared light.
ii. Bathymetric LiDAR uses water-penetrating green light to measure seafloor and riverbed elevations.

3. Large Footprint LiDAR uses full waveforms and averages LiDAR returns in 20m footprints. But it’s very difficult to get terrain from large footprint LiDAR because you get a pulse return based on a larger area which could be sloping. There are generally less applications for large footprint LiDAR. Only SLICER (Scanning Lidar Imager of Canopies by Echo Recovery) and LVIS (Laser Vegetation Imaging Sensor), both built by NASA and are experimental.

4. Ground-based LiDAR sits on a tripod and scans the hemisphere. Ground-based LiDAR is good for scanning buildings. It’s used in geology, forestry, heritage preservation and construction applications.

水土保持局監控雨量站點加權係數研究

現行做法如下：

1. 10分鐘、時雨量、3小時、6小時，及24小時雨量係指以目前時間往前推一定時間累積降雨。
2. 雨場分割ETR1：係指同一雨場，自降雨開始至目前之累積雨量（不作任何拆減）；且雨場分別之標準係以 6 小時內總雨量小於 4mm 時作為雨場結束點。
3. 前期降雨ETR2：即有效累積雨量，其計算方式如下：
   
4. 警戒說明:
5. • 已發布紅色警戒
   • 已發布黃色警戒
   • 接近紅色警戒(有效累積雨量逾土石流警戒值之70%)
   • 達黃色警戒發布標準(有效累積雨量+預測雨量大於土石流警戒值且目前有效累積雨量逾土石流警戒值之30%(警戒值<300)、40%(警戒值>=400))
6. 頻率年資料說明
   • ★:逾50年雨量資料(水土保持工程採用50年之重現期距規劃設計)
   • ★★:逾200年雨量資料(水土保持工程採用50年之重現期距規劃設計)

警戒值動態調整：

1. ＊一級調整 3hr累積雨量>=200mm (原警戒值400mm以下,調降100mm；原警戒值450mm以上,調降150mm)
2. ＃二級調整 3hr累積雨量>=150mm (原警戒值400mm以下,調降50mm；原警戒值450mm以上,調降100mm)
3. ＠三級調整 2hr累積雨量>=100mm (原警戒值400mm以下,調降50mm；原警戒值450mm以上,維持不變)

 

未來研究方向，將針對其加權係數稍作調整，以更符合實際發生情況。

20160604鋒面系統分析

分享幾張作品

目前還在做前端及後端優化工作，初步成品請大家多多指教了

利用Voronoi Polygons tool 製作台灣地區雨量站的多邊形法

Voronoi polygons is a systematic way to divide spaces into a number of regions using a set of points specified at the beginning.

For each point there will be a corresponding region that consists of the points closer to that points than any other. These regions are called voronoi cells.

Voronoi polygons are useful in that they allow mappers to visually see the distribution of points through shapes.

更多的定義可以參考Wiki click here.

水土保持局台中分局>>>整體性治山防災（中長程）計畫 102至105年度（第二期）

一、計畫目標

本期計畫延續第一期計畫目標，持續結合「治山」、「防災」、「保育」及「永續」等四個策略目標，期達成保育水土資源、涵養水源、減免災害、促進土地合理利用、增進國民福祉等主要目標，並戮力朝向土石流災害傷亡趨近於零及國土永續經營之願景。

二、計畫主要辦理工作項目

本計畫持續以軟體防災結合硬體減災，強化土石流監測及防災，並加速辦理各項治山防災工作，以有效減輕災害規模，各分項子計畫分述如下：