gis-landslide meeting お手軽地形測量 2011-11-26
TRANSCRIPT
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Yuichi S. Hayakawa
レーザ距離計とGNSSを用いた現場でのお手軽地形図作成法
早川裕弌東京大学空間情報科学研究センター
2011.11.26 GIS-Landslide Workshop 3rd
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Yuichi S. Hayakawa
Introduction
Detailed topographic maps/data are necessary as the basic material for geoscientific field surveys
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Yuichi S. Hayakawa
How to get a topo map?Freehand Classical methods High-tech methods
easy
inaccurate accurate
effortful
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Yuichi S. Hayakawa
Disadvantages of high-tech methods
• High resolution satellite images and/or airphotos are still expensive. In some countries their acquisition is limited due to military reason.
• Data processing of satellite/airphotoimages for topographic data is often cost-ineffective (time & money).
• Airboren/terrestrial laser scanning is also time-consuming or restricted in rural areas abroad.
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Yuichi S. Hayakawa
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Yuichi S. Hayakawa
Use of portable devices: LRF and DGNSS
• LRF; laser range finder• DGNSS; differential global navigation
satellite system (incl. GPS, GLONASS) Quick acquisition of accurate maps
• Advantages: portability, price
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Yuichi S. Hayakawa
FIELD MEASUREMENT METHODFor acquisition of DEMs in field
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Yuichi S. Hayakawa
Portable system for topographic measurement
• LRF with digital compass– Impulse 200 LR &
Mapstar by LaserTech• Portable DGNSS
– MobileMapper Pro by Thales Navigation
• Monopod with bipod legs
• Operating PC(早川・津村, 2008;
Hayakawa and Tsumura, 2009.)
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Yuichi S. Hayakawa
Another combination
Trimble GeoXH 6000
LaserTechTruPulse 360B
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Yuichi S. Hayakawa
Field measurement
Basepoint:DGNSS positioning
Laser measurements(distance, angles)
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Yuichi S. Hayakawa
Measuring point:DGNSS positioning
Laser measurements(distance, angles)
Measurement by DGPS + LRF
(Base point:the first measuring point)
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Yuichi S. Hayakawa
Data processing
Distance (horizontal)
Height (vertical)
Direct distanceElevation angleAzimuth(mag. north)
Raw Computed
Horizontal distanceHeightAzimuth(true north)
XYZ
(x, y, z) geographic coordinate by DGNSS
(BaseTarget)
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Yuichi S. Hayakawa
Hacıtuğrul Tepe
Ankara
Study site
Turkey
SyiraIraq
Bulgaria Georgia
Greece
300 km
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Yuichi S. Hayakawa
600 m !!
Hacıtuğrul Tepe
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Yuichi S. Hayakawa
Base point coordinate32°13’16.9″E, 32°42’19.9″N, 915.8 m a.s.l.
Time for measurement 4 days for overall topography and 5 days for detailed local topographyBy 2 persons
Area and number of points approx. 1 km2
17,549 pts (13,217 pts after error reduction)11,017 pts (10,908 pts after error reduction)
Interpolation Method: Ordinary KrigingModel: Exponential for overall, Linear for localNugget effect: On Resolution (cell size): 4 m for overall, 0.2 m for local
Data property
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Yuichi S. Hayakawa
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Distance (m)
Actual dataSphericalCircularExponentialGaussianLinear with sill
Kriging interpolation (exponential)
4-m DEMSemivariogramPoint cloud
Overall topography
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Yuichi S. Hayakawa
Topographic map of HacıtuğrulTepe
- 4 days by 2 operators- DEM resolution: 4 m- Contour interval: 0.5 m- Accuracy: ~1 m
300 m
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Yuichi S. Hayakawa
927 m
890 m
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Distance (m)
Actual dataSphericalCircularExponentialGaussianLinear with sill
Kriging interpolation (linear)
20-cm DEMSemivariogramPoint cloud
Partially high-resolution map
Point density is flexible.(trade-off with time)
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Yuichi S. Hayakawa
0 60 12030 m
10-cm contour map and hillshade image
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Yuichi S. Hayakawa
Interpolation
Point cloud DEM + Contour
Ras Jibsh, Oman
Kriging
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Yuichi S. Hayakawa
Measurements of small tepes(~100 m)
Quick, accurate mapping
Zirayet Tepe Kale Höyük Dolma Tepe Hazarşah
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Yuichi S. Hayakawa
Piz dal Büz(A) (B)
(C)
RTK-GPS mobile
DGPS base
RTK-GPS base
LRF
DGPS mobile
Operating PC
A rock glacier in Swiss Alps
Nr. Elevation (m) Difference (m) RTK-GPS Laser-DEM
01 2920.64 2919.88 -0.76 02 2841.43 2841.48 0.05 03 2840.07 2839.17 -0.90 04 2841.23 2841.71 0.48 05 2844.17 2843.99 -0.18 06 2854.75 2855.36 0.61 07 2853.74 2853.52 -0.22 08 2851.39 2851.70 0.31 09 2857.26 2857.42 0.16 10 2854.35 2854.16 -0.19 11 2864.24 2864.33 0.09 12 2865.56 2863.31 -2.25 13 2872.10 2873.22 1.12 14 2870.95 2871.60 0.65 15 2874.76 2875.90 1.14 Average: 0.01 Standard deviation: 0.83
Accuracy: 0.8 mcomparison with RTK-GNSS
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Yuichi S. Hayakawa
Comparison with other DEMs
We can recently use various, worldwide topographic data, but their resolution is often low.
– How accurate or reliable? – Appropriate for what scale?
Here we compare several DEMs from different sources:
[ SRTM, GDEM, PRISM DEM, Field DEM ]
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Yuichi S. Hayakawa
DEMs to compare• SRTM
– CGIAR-SCI (Filled GeoTIFF/ASCII), ver. 4– Resolution = 90 m
• GDEM– METI/NASA, ver. 1– Resolution = 30 m
cf. 2011/10/17 ver. 2 release• PRISM DEM
– AIST: GEOGrid PRISM DEM processing service– Resolution = 10 m
• Field DEM– LRF/DGNSS measurement– Resolution = 2 m
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Yuichi S. Hayakawa
Study site
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Yuichi S. Hayakawa
Eğriköy
• Early Bronze – Rome/Byzantine• Located at shoreline of old lake
(Sultansazligi)• 250 m long, 10 m high• Triangular shape (onigiri)
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Yuichi S. Hayakawa
EğriköyField DEM >>> PRISM DEM >> SRTM > GDEM
SRTM(Contour=2m,10m)
GDEM(Contour=2m,10m)
PRISM DEM(Contour=2m,10m)
Field DEM(Contour=1m)
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Yuichi S. Hayakawa
0
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LRF
PRISM(10^2)
GDEM
SRTM(10^-1)
Elevation (m) Slope (degrees)
Curvature (m-1)
% %
%
Histograms
SRTMGDEMPRISM DEMField DEM
SRTM (10-1)GDEMPRISM DEM (102)Field DEM
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Yuichi S. Hayakawa
ResultsApplicability
– 103 m scale objects: SRTM, GDEM, PRISM DEM, Field DEM
– 102 m scale objects: SRTM, GDEM, PRISM DEM, Field DEM
– 100–101 m scale objects: SRTM, GDEM, PRISM DEM, Field DEM
Advantages / Disadvantages– SRTM
• OK: Wide area / NG: Small (<102 m) objects– GDEM
• OK: Mountainous steep terrain / NG: Lowlands– PRISM DEM
• OK: Wide area, small objects (~102 m) / NG: Noisy– Field DEM
• OK: ~100 m very small objects / NG: Wide area (>100 km2)
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Yuichi S. Hayakawa
Remarks• >102 m scale objects / >102 km2 extent
– SRTM• 102 m scale objects / 100–102 km2 extent
– PRISM DEM• 100–101 m scale objects / 10-1–100 km2 extent
– Field DEM
cf. Laser scanning technologies– ALS (Airborne laser scan)
• 100–101 m scale object / >100 km2 extent• Fine resolution, wide area
– TLS (Terrestrial laser scan)• 10-2–101 m scale object / 10-1–100 km2 extent• Very fine resolution, relatively narrow area
Select appropriate methods for appropriate scales/extent