都市基盤工学 ( リモートセンシングと GIS 入門 ) Introduction to Remote Sensing and GIS. Ground-based sensors 地上からのセンサ 第 4 回 千葉大学大学院融合理工学府

Transcription

1 都市基盤工学 ( リモートセンシングと GIS 入門 ) Introduction to Remote Sensing and GIS 第 4 回 千葉大学大学院融合理工学府 Graduate School of Science and Engineering, Chiba University 地球環境科学専攻都市環境システムコース Department of Urban Environment Systems 劉ウェン Wen LIU 1 講義予定 Lecture Schedule (1) 2018 年 4 月 11 日 ( 水 ) イントロダクション Introduction (2) 2018 年 4 月 18 日 ( 水 ) リモセンの基礎原理 1 Fundamentals of RS #1 (3) 2018 年 4 月 25 日 ( 水 ) リモセンの基礎原理 2 Fundamentals of RS #2 (4) 2018 年 5 月 9 日 ( 水 ) 衛星とセンサ 1 Satellites and sensors #1 Liu (5) 2018 年 5 月 16 日 ( 水 ) 衛星とセンサ 2 Satellites and sensors #2 (6) 2018 年 5 月 23 日 ( 水 ) 衛星とセンサ 3 Satellites and sensors #3 (7) 2018 年 5 月 30 日 ( 水 ) 画像解析 1 Image Analysis #1 Liu (7) 2018 年 6 月 6 日 ( 水 ) 画像解析 2 Image Analysis #2 Liu (9) 2018 年 6 月 13 日 ( 水 ) GIS の基礎 1 Basics of GIS #1 Maruyama (10) 2018 年 6 月 20 日 ( 水 )GIS の基礎 2 Basics of GIS #1 Maruyama (11) 2018 年 6 月 27 日 ( 水 ) マイクロ波リモセン #1 Microwave RS #1 Liu (12) 2018 年 7 月 4 日 ( 水 )GIS の基礎 3 Basics of GIS #3 Maruyama (13) 2018 年 7 月 11 日 ( 水 ) 課題発表 1 Presentation by Students #1 (14) 2018 年 7 月 18 日 ( 水 ) 課題発表 2 Presentation by Students #2 (15) 2018 年 7 月 25 日 ( 水 ) 課題発表 3 Presentation by Students #3 2 Various Platforms on the Ground, in the Air, and in Space Platforms for remote sensors may be situated on the ground, on an aircraft or balloon (or some other platform within the Earth's atmosphere), or on a spacecraft or satellite outside of the Earth's atmosphere. プラットフォームは地上, 空中, 宇宙 Ground-based sensors 地上からのセンサ Ground-based sensors are often used to record detailed information about the surface. 地表の詳細な情報を得る Sensors may be placed on a ladder, scaffolding, tall building, cherry-picker, crane, etc. 梯子, 足場, 高層ビル, クレーン Mobile Laser Scanner Ground Penetration Radar Remote sensing in early days 3 High-position camera Nasca Lines, Peru Ground Laser Scanner 4

2 Aircraft 航空機 Aerial platforms are primarily stable wing aircraft, although helicopters are occasionally used. 固定翼航空機, ペリコプターなど Aircraft are often used to collect very detailed images and facilitate the collection of data over virtually any portion of the Earth s surface at any time. いつでもどこでも行ける Start Point Unmanned Aerial Vehicles (UAVs) 無人航空機 Z Y X Observation Point Radio Control Helicopter DSM Dr. Y. Honda, CEReS, Chiba Univ. Kunikaze III, GSI Disaster reconnaissance Small Helicopter-type UAV Drone Air Photo Service Co. DJI Phantom 2 Aerial photo 5 AR.Drone 2.0 MS-06LB Nonami Lab 6 Structure from Motion (SfM) Unknown camera viewpoints Reconstruct Scene geometry Camera motion Construction of 3D model of structures from many images with unknown positions 複数の画像からカメラの撮影位置を自動的に推定し 3D モデルを構築する技術. Space Shuttle スペースシャトル On February 11, 2000, the Shuttle Radar Topography Mission (SRTM) payload onboard Space Shuttle Endeavour launched into space. With its radars sweeping most of the Earth s surfaces, SRTM acquired enough data during its ten days of operation to obtain the most complete near-global high-resolution database of the Earth s topography. 毛利さんのデータ The Shuttle Radar Topography Mission maps 80% of the Earth s terrain at 30 meter resolution. 地表の80% の標高データを30m 解像度で取得 p 1 p 4 p 3 p 5 p 2 p 7 minimize f(r, T, P) p6 Camera 1 Camera 3 Camera 2 R 1,t 1 R R 2,t 3,t 数字は観測回数 8

3 SRTM Data 1-arc second (30 meter) SRTM data postings of the continental United States can now be obtained via the USGS EDC Seamless Distribution System. 1 秒メッシュ (30m) の標高データは米国について公開 As new 3-arc second (90 meter) international continental datasets are processed and received, USGS will distribute this data via the Seamless Data Distribution System. 世界データは3 秒メッシュ (90m) で公開 2014 年より30mで世界大半を公開開始 arc second: a unit equal to 1/3600th of a degree the newly available full-resolution data 3D Representation of satellite images with SRTM 90m DEM 衛星画像とSRTM 90m DEMによる3D 表示 2004 年インド洋津波,Khaolak, Phan-ga, Thailand 2008 年中国 四川地震 Before 2004/12/31 ASTER After QuickBird KHAO LAK, PHANG NGA, THAILAND 2002/11/ Satellites 人工衛星 In space, remote sensing is conducted commonly from satellites. 宇宙からは人工衛星 Man-made satellites include those platforms launched for remote sensing, communication, and telemetry (location and navigation) purposes. 衛星はリモセン, 通信, 位置観測など Because of their orbits, satellites permit repetitive coverage of the Earth s surface on a continuing basis. 衛星は繰り返し連続的に地球をカバー Orbits of Satellites 衛星軌道 Orbit selection can vary in terms of altitude and their orientation and rotation relative to the Earth. 軌道は高度, 方向と地球に対する回転で決まる Satellites at very high altitudes, which view the same portion of the Earth s surface at all times, have geostationary orbits. 静止衛星は高度が高い Many remote sensing platforms are designed to follow a near polar orbit (basically north-south) which, in conjunction with the Earth s rotation (west-east), allows them to cover most of the Earth s surface 地球観測衛星は準極軌道 Cost is often a significant factor in choosing among the various platform options. 費用がプラットフォームの選択要因 11 Orbit of Terra 12

4 Geostationary Orbits 静止衛星 The geostationary satellites, at altitudes of approximately 36,000 km, revolve at speeds which match the rotation of the Earth so they seem stationary, relative to the Earth s surface. 地球の自転と同じ速度で赤道上の上空に位置する This allows the satellites to observe and collect information continuously over specific areas. Weather and communications satellites commonly have these types of orbits. 特定の地域を常時観測, 気象衛星や通信衛星 Due to their high altitude, some geostationary weather satellites can monitor weather and cloud patterns covering an entire hemisphere of the Earth. ほぼ半球を観測可能 Near-polar Orbits 準極軌道 Near-polar orbits are so named for the inclination of the orbit relative to a line running between the North and South poles. 極を結ぶ面よりやや傾く Many of these satellite orbits are also sun-synchronous such that they cover each area of the world at a constant local time of day. 同じ時間に回帰をする ( 太陽同期 ) At any given latitude, the position of the sun in the sky as the satellite passes overhead will be the same within the same season. 同緯度では衛星通過時刻の太陽位置は季節ごとに同じ This ensures consistent illumination conditions when acquiring images in a specific season over successive years, or over a particular area over a series of days. 永年に渡る観測データで同じ日照条件 This is an important factor for monitoring changes between images or for mosaicking adjacent images together. 環境変化把握やモザイク画像作成が可能 Ascending and Descending Paths 上昇 下降軌道 Most of the remote sensing satellites are in near-polar orbits, which means that the satellite travels northwards (ascending) on one side of the Earth and then toward the southern pole (descending) on the second half of its orbit. 準極軌道では北向きが上昇軌道, 南向きが下降軌道 Orbits of earth observation satellites 衛星は今どこにいるか? If the orbit is also sun-synchronous, the ascending path is most likely on the shadowed side of the Earth while the descending path is on the sunlit side. 太陽同期軌道では上昇が夜間, 下降が日中 Sensors recording reflected solar energy only image the surface on a descending path. Active sensors which provide their own illumination or passive sensors that record emitted (e.g. thermal) radiation can also image the surface on ascending paths. 太陽エネルギーを使う光学センサは下降軌道で画像取得 15 UTC: Universal Time Coordinate UTC+9 hours in Japan 16

5 Swath 観測幅 走査幅 As a satellite revolves around the Earth, the sensor sees a certain portion of the Earth s surface. The area imaged on the surface, is referred to as the swath. 衛星の軌道から観測される範囲を観測幅という Swath and spatial resolution of various satellites If seen from the Earth, the satellite is shifting westward because the Earth is rotating. This apparent movement allows the satellite swath to cover a new area with each consecutive path. 地球の自転により, 軌道は見かけ上, 西に移動 ETM+ Spatial Resolution Relative to Other Sensors a_properties/prog_sect6_2.html The satellite s orbit and the rotation of the Earth work together to allow complete coverage of the Earth s surface, after it has completed one complete cycle of orbits. 衛星軌道と地球の自転により,1 周期の軌道で地球全域をカバー Orbit Cycle and Revisit Period 軌道周期と回帰周期 An orbit cycle will be completed when the satellite retraces its path, passing over the same point on the Earth s surface directly below the satellite (called the nadir point) for a second time. 直下の同じ地点に来る時間は軌道周期 Steerable sensors can view an area (off-nadir) before and after the orbit passes over a target, thus making the revisit period less than the orbit cycle time. 直下でない観測域に入る時間を回帰周期 The revisit period is an important consideration for a number of monitoring applications, especially when frequent imaging is required (e.g., to monitor the spread of an oil spill). 回帰周期は頻繁な観測が必要な場合に重要 In near-polar orbits, areas at high latitudes will be imaged more frequently than the equatorial zone due to the increasing overlap in adjacent swaths. 準極軌道では高緯度地域は頻繁に観測 = Path (orbit) = Path Number = USGS/EROS Data Center - Sioux Falls, SD = Svalbaard, Norway = Poker Flat, Alaska Paths of Landsat Path and Row of Landsat 20

6 Spatial Resolution of Satellites 空間解像度 Images where only large features are visible are said to have coarse or low resolution. 荒い ( 低 ) 解像度 ( 分解能 ) In fine or high resolution images, small objects can be detected. Military sensors for example, are designed to view as much detail as possible, and therefore have very fine resolution. 細かい ( 高 ) 解像度 => 軍事衛星 Commercial satellites provide imagery with resolutions varying from a few meters to several kilometers. 商業衛星は様々な解像度 Generally speaking, the finer the resolution, the less total ground area can be seen. 解像度が高いと写す範囲は狭い 21 Multispectral Sensors of Moderate-Resolution Satellites 主な中解像度衛星のマルチスペクトル センサ Sponsor Lifespan Spatial Resolution Swath Spectral Bands Other Sensor Specs m MS 185x172 MS 7 Bands VNIR-TIR 120m TIR km Comparison of 1m (left), 10m (middle), 30m (right) spatial resolution 22 Multispectral IRS-P6 Sensor - Satellite Landsat 4 & 5 TM NASA/NOA A/USGS Landsat 7 ETM+ NASA/NOA A/USGS SPOT 4 LISS-4, LISS-3 & AWiFS April 15th ongoing** 6 yrs mission 2xHRV-IR CNES March & ongoing? Vegetation INDIA (ISRO) Oct ongoing 5.8, 23.5 & 56m 23.9, 141 LISS-4 3 bands nm & 740 km CBERS-2 CCD Camera ASTER Terra MITI/NASA December 15m VNIR 60 km x 3 bands VNIR nm, km 6 yrs mission 30m SWIR 6 bands SWIR nm, 90m TIR 5 bands TIR nm, Bands for stereoscopy 780- CHINA- BRAZIL Repeat Cycle 16 days 15m Pan 185x172 Pan nm ** Data quality 16 days km dropped significantly 30m MS 5 Bands VNIR since the SLC 60m TIR 2 Bands SWIR failure in June 1 Band TIR m Pan 60x60 km MS 4 bands ( , 610- Also Vegetation 3 to , , nm) Instrument at days 20m MS Pan ( nm) 1.1km pixel ±27 inclination ASTER DEM product available, about 30m accuracy. 24 days 16 days Oct yrs 20m CCD(high-res.,5bands) 113 km 26 days ALOS AVNIR-2 JAXA Jan m MS 4 bands 46 days PRISM JAXA Jan m Pan 1 band Sensors of High-Resolution Satellites 高解像度衛星とセンサ High Resolution Sensor - Satellite ORBView-3 Quickbird-2 IKONOS-2 EROS 1A SPOT 5a HGR & Vegetatio n Sponsor Lifespan Spatial Resolutio Orbimage DigitalGlob e Space Imaging Swath Spectral Bands Other Sensor Specs June m Pan 8 km MS 4 bands ( , , , nm) 5 yrs mission 4m MS Pan ( nm) Oct ongoing 0.61m Pan 16.5 km MS 4 bands ( , , , 760- Sept ongoing 2.44m MS 165 km track 890nm) Pan ( nm) Repeat Cycle QB 2 polar orbit days ±30 in all directions Stereo ±26 inclination 1m Pan 11.3 km MS 4 bands ( , wide at nadir , , nm) 4m MS Pan ( nm) 11 bits data West Dec m Pan 12.6x12. Pan ( nm) Indian ongoing 6 km Spot Image May & 5m Pan 60 km > 5 yrs mission? MS 4 bands ( , , , ) ±45 off nadir < 3 days Also Vegetation Instrument 1-3 days days 3 to 26 days 10m MS Pan nm ±31 inclination 20m SWIR IRS-1C & 1D LISS3 & INDIA 1C: Dec. 95 5m Pan 70x70 k Pan nm Pan ±26 24 days WiFS sensors (ISRO) - ongoing 1D: Sept m MS m Pan 142x142 MS 4 bands ( , km MSS , , inclination 5-24 offnadir Pan 180m WiFS 774x774 WiFS 2 bands ( , km WiFS nm) WorldView-1 DigitalGlobe Sept m Pan 17.6km Pan 1.7 days WorldView-2 DigitalGlobe Oct m Pan 16.4km MS 8 bands (1.8m) + Pan (0.5m) 1.1 days GeoEye-1 GeoEye Sept m Pan 15.2km MS bands (1.6m) + Pan (0.4m) 2.1 days WorldView-3 DigitalGlob Aug m Pan 13.1km MS bands (1.24m) + Pan (0.31m) 1 day 23 Spectral Resolution スペクトル分解能 Different classes of features and details in an image can often be distinguished by comparing their responses over distinct wavelength ranges. Broad classes, such as water and vegetation, can usually be separated using very broad wavelength ranges - the visible and near infrared. 波長に依存する反射特性は物質を見分けるのに利用 Other more specific classes, such as different rock types, may not be easily distinguishable using these broad wavelength ranges and would require comparison at much finer wavelength ranges to separate them. より詳細な分類には細かい反射特性が必要 Reflectance of Different Rock Types 24

7 Multi-spectral and Hyper-spectral Sensors マルチスペクトル, ハイパースペクトル センサ Many remote sensing systems record energy over several separate wavelength ranges at various spectral resolutions. These are referred to as multi-spectral sensors. 通常の光学センサはマルチスペクトル Advanced multi-spectral sensors called hyperspectral sensors, detect hundreds of very narrow spectral bands throughout the visible, near-ir, and mid-ir portions of the EM spectrum. 百を越えるような多数のバンドを持つセンサはハイパースペクトル Hyperspectral Sensors 主なハイパースペクトル衛星センサ Hyperspectral Sensor - Satellite Sponsor Lifespan Spatial Resolution Swath Spectral Bands Other Sensor Specs EO-1 Hyperion NASA Dec m 7.5 km x 220 bands 400nm to ongoing! 100 km Grating Imaging Spec (sept. 2003) Grating Imaging Spec 1 yr mission EO-1 LEISA AC NASA 12/1/ m 7.5 km x 309 Bands 1 yr mission 100 km Wedge Imaging Spec Envisat-1 MERIS ESA May m 1150 km 15 bands programmable 5 identical Aerospatiale 5 and sensors France, mission 1200m Cannes, ACRI global ADEOS-2 GLI NASDA Dec /1000m 19 bands Failed Oct prematurely on 3 yrs design 4 bands october bands 7 bands Repeat Cycle 35 days Their very high spectral resolution facilitates fine discrimination between different targets based on their spectral response in each of the narrow bands. ハイパースペクトル センサは物質の詳細な識別に利用 25 Current and planned hyperspectral civilian spaceborne hyperspectral imagers. VISNIR: Visible and near-ir. SWIR: Short-wave IR. TIR: Thermal IR Terra-MODIS (Moderate Resolution Imaging Spectroradiometer) Sees every point on our world every 1-2 days in 36 discrete spectral bands. Primary Use Band Bandwidth Land/Cloud Boundaries Land/Cloud Properties Ocean Color/ Phytoplankton/ Biogeochemistry Atmospheric Water Vapor Surface/Cloud Temperature Atmospheric Temperature Cirrus Clouds Water Vapor Ozone Surface/Cloud Temperature Cloud Top Altitude Bands 1 to 19, nm; Bands 20-36, μm Spatial Resolution: 250 m (bands 1-2) 250m 1km (at nadir): 500 m (bands 3-7) 1000 m (bands 8-36) 500m 27 Radiometric Resolution 放射分解能 Every time an image is acquired on film or by a sensor, its sensitivity to the magnitude of the EM energy determines the radiometric resolution. 電磁エネルギーの大きさに対する感度をいう The radiometric resolution of an imaging system describes its ability to discriminate very slight differences in energy. The finer the radiometric resolution of a sensor, the more sensitive it is to detecting small differences in reflected or emitted energy. 放射分解能が高いと放射特性の違いを見分けれる Quantitization 量子化 ( 濃度値の離散化 ) 2-bit Image 8-bit Image (4 grey levels) (256 grey levels) 28

8 Temporal Resolution 時間分解能 In addition to spatial, spectral, and radiometric resolution, the concept of temporal resolution is also important to consider in a remote sensing system. 時間分解能 ( 観測頻度 ) も重要 The absolute temporal resolution of a remote sensing system to image the exact same area at the same viewing angle a second time is equal to the revisit period. 回帰日数で, 同じ地域を同じ角度でみることができる Due to overlap in the imaging swaths of adjacent orbits for most satellites and the increase in this overlap with increasing latitude, some areas of the Earth tend to be re-imaged more frequently. 観測幅の重なりにより高緯度ではより頻繁な観測 Multi-temporal Imagery 多時期画像の重要性 The time factor in imaging is important when: Persistent clouds offer limited clear views of the Earth s surface (often in the tropics) 天候による観測可能日の制限 Short-lived phenomena (floods, oil slicks, etc.) need to be imaged 短期間の現象の撮影 Multi-temporal comparisons are required (e.g. the spread of a forest disease from one year to the next) 多時期による比較 The changing appearance of a feature over time can be used to distinguish it from near-similar features (wheat / corn) 時間変化による似たものの分類 Some satellite systems are able to point their sensors to image the same area between different satellite paths. センサの向きを変えて他の軌道から観測できる衛星もある. 29 RapidEye five satellites constellation 30 Banda Ache before and after the Tsunami False Color Composite 0 500m Seasonal change of NDVI by NOAA Dr. Y. Honda, CEReS, Chiba Univ. 32