SAR Interferometric Baseline Refinement Based on Flat-Earth Phase without a Ground Control Point

Interferometric baseline estimation is a key procedure of interferometric synthetic aperture radar (SAR) data processing. The error of the interferometric baseline affects not only the removal of the flat-earth phase, but also the transformation coefficient between the topographic phase and elevation, which will affect the topographic phase removal for differential interferometric SAR (D-InSAR) and the accuracy of the final generated digital elevation model (DEM) product for interferometric synthetic aperture (InSAR). To obtain a highly accurate interferometric baseline, this paper firstly investigates the geometry of InSAR imaging and establishes a rigorous relationship between the interferometric baseline and the flat-earth phase. Then, a baseline refinement method without a ground control point (GCP) is proposed, where a relevant theoretical model and resolving method are developed. Synthetic and real SAR datasets are used in the experiments, and a comparison with the conventional least-square (LS) baseline refinement method is made. The results demonstrate that the proposed method exhibits an obvious improvement over the conventional LS method, with percentages of up to 51.5% in the cross-track direction. Therefore, the proposed method is effective and advantageous.

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OPTIMIZATION OF GROUND CONTROL POINT (GCP) CONFIGURATION FOR UNMANNED AERIAL VEHICLE (UAV) SURVEY USING STRUCTURE FROM MOTION (SFM)

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xlii-4-w12-167-2019 ◽

2019 ◽

Vol XLII-4/W12 ◽

pp. 167-174 ◽

Cited By ~ 6

Author(s):

J. K. S. Villanueva ◽

A. C. Blanco

Keyword(s):

Structure From Motion ◽

Reference Data ◽

Control Point ◽

Ground Control ◽

Ground Control Point ◽

Center Configuration ◽

Digital Elevation ◽

Aerial Vehicle ◽

Elevation Model ◽

The Impact

Abstract. This research presents a method in assessing the impact of Ground Control Point (GCP) distribution, quantity, and inter-GCP distances on the output Digital Elevation Model (DEM) by utilizing SfM and GIS. The study was carried out in a quarry site to assess the impacts of these parameters on the accuracy of accurate volumetric measurements UAV derivatives. Based on GCP Root Mean Square Error (RMSE) and surface checkpoint error (SCE), results showed that the best configuration is the evenly distributed GCP set (1.58&thinsp;m average RMSE, 1.30&thinsp;m average SCE). Configurations clumped to edge and distributed to edge follow suit with respective RMSE (SCE) of 2.53&thinsp;m (2.13&thinsp;m) and 3.11&thinsp;m (2.54&thinsp;m). The clumped to center configuration yielded 6.23&thinsp;m RMSE and 4.66&thinsp;m SCE. As the number of GCPs used increase, the RMSE and SCE are observed to decrease consistently for all configurations. Further iteration of the best configuration showed that from RMSE of 4.11&thinsp;m when 4 GCPs are used, there is a drastic decrease to 0.86&thinsp;m once 10 GCPs are used. From that quantity, only centimeter differences can be observed until the full set of 24 GCPs have been used with a 0.012&thinsp;m error. This is reflected in the stockpile measurement when the iteration results are compared to the reference data. The dataset processed with a minimum of 4 GCPs have a 606,991.43&thinsp;m3 difference, whereas the dataset processed with 23 out of 24 has a 791.12&thinsp;m3 difference from the reference data. The accuracy of the SfM-based DEM increases with the quantity of the GCPs used with an even distribution.

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PENENTUAN GARIS PANTAI MENGGUNAKAN FOTO UDARA DARI WAHANA TANPA AWAK (Studi Kasus Pantai Ujong Batee Aceh)

Seminar Nasional Geomatika ◽

10.24895/sng.2020.0-0.1185 ◽

2021 ◽

pp. 707

Author(s):

Herjuno Gularso ◽

Andri Daniel Parapat ◽

Teguh Sulistian ◽

Alfian Adi Atmaja

Keyword(s):

Digital Elevation Model ◽

Point Cloud ◽

Control Point ◽

Ground Control ◽

Check Point ◽

Ground Sample ◽

Ground Control Point ◽

Digital Elevation ◽

Elevation Model ◽

Sample Distance

Garis pantai merujuk Undang-undang No 4 tahun 2011 pasal 13 merupakan garis pertemuan antara daratan dengan lautan yang dipengaruhi oleh pasang surut air laut. Pembentukan garis pantai membutuhkan data Digital Elevation Model (DEM) diwilayah pesisir dengan resolusi dan ketelitian tinggi, sementara teknologi foto udara memiliki kemampuan dalam hal ekstraksi point ketinggian (point cloud) dari titik sekutu antar foto udara yang bertampalan dan juga memiliki kelebihan menghemat waktu pekerjaan dan biaya jika dibandingkan dengan pengukuran terestris. Penelitian ini bertujuan untuk menguji hasil pembentukan DEM dari data foto udara yang selanjutnya digunakan untuk pembentukan garis pantai di pantai Ujong Batee Aceh. Proses pengumpulan data menggunaan wahana Multi rotor DJI Mavic Pro. Jumlah titik Ground Control Point (GCP) adalah 10 titik yang tersebar secara merata untuk seluruh area yang dipetakan. Hasil Ground Sample Distance adalah 1,97 cm/pixel dengan cakupan area yaitu 16,8 hektar. Hasil uji akurasi vertikal DEM menggunakan 167 Independent Check Point (ICP) adalah sebesar 0,863 m, dapat disimpulkan bahwa data foto udara kamera non-metrik dalam penelitian ini memenuhi ketelitian vertikal peta RBI pada skala 1:5.000 kelas I (SNI Ketelitian peta dasar 8202:2019). Pembentukan garis pantai menggunakan DEM dari foto udara yang sudah dikoreksi menggunakan model pasut BIG sehingga datum vertikal dari DEM adalah muka air rata- rata. Garis pantai yang terbentuk pada lokasi penelitian hanya garis pantai pasang tertinggi dan muka air laut rata-rata. Pemotretan udara untuk mendapatkan DEM diwilayah pesisir sebaiknya dilakukan pada saat air surut untuk memperoleh garis pantai air muka laut rata-rata dan pasang tertinggi.

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Evaluation of Low Cost Digital Cameras for Producing Photogrammetric Output from UAV

International Journal of Engineering & Technology ◽

10.14419/ijet.v7i2.29.14258 ◽

2018 ◽

Vol 7 (2.29) ◽

pp. 792 ◽

Cited By ~ 1

Author(s):

Syafiq Sukor ◽

Anuar Ahmad

Keyword(s):

Global Positioning System ◽

Mean Squared Error ◽

Low Cost ◽

Control Point ◽

Ground Control ◽

Digital Cameras ◽

Squared Error ◽

Digital Elevation ◽

Global Positioning ◽

Elevation Model

Recently there a lot of improvement in digital photogrammetry and this allow photogrammetry to become faster and cheaper . This study discuss about two type of low cost camera which is the compact camera (Canon Power Shot SX230 ) and action camera (Xiaomi yi) where both of them have different lens distortion. This study is conducted within UTM (Universiti Teknologi Malaysia) Skudai campus at Kolej Tun Razak. Both of the Canon Power Shot SX230 and Xiaomi yi camera would be attach to the UAV to take aerial photo with three different altitude which is 60 meter, 80 meter and 100 meter with a similar flight path. Check point (CPs) and Ground control point (GCPs) were also established using rapid static technique of Global Positioning System (GPS) and Total Station. The Canon Power Shot SX230 and Xiaomi yi camera is then calibrated using checkboard calibration this is done by using Agisoft Lens software. Then all of the pictures that been taken by the Canon Power Shot SX230 and the Xiaomi yi would be processed by using Agisoft Photoscan software to generate Digital Elevation Model (DEM), orthophoto and contour line. The accuracy of DEM was determined based on Root Mean Squared Error (RMSE) value. Both of the result is then analyze visually and statically. Overall both of the camera gives a slight different in accuracy.

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Assessing the accuracy of river channel bathymetry measurements using an RTK rotary-winged Unmanned Aerial Vehicle (UAV) with varying Ground Control Point (GCP) number and placement

10.5194/egusphere-egu2020-1534 ◽

2020 ◽

Author(s):

Ian Maddock ◽

Josie Lynch

Keyword(s):

Control Point ◽

Base Station ◽

River Channel ◽

Ground Control ◽

Time Saving ◽

Digital Elevation ◽

Wadeable Streams ◽

Rtk Gps ◽

Elevation Model ◽

Submerged Area

Previous studies have established the ability to map river channel bathymetry accurately in clear water, shallow wadeable streams using imagery from Unmanned Aerial Vehicles (UAVs), Structure-from-Motion (SfM) photogrammetry and the application of refraction correction. However, because standard rotary-winged UAVs geotag imagery at a relatively low accuracy, there has been a need to use Ground Control Points (GCPs) to georeference the Digital Elevation Model (DEM). This is problematic in that is requires the operators to navigate around the site to place, survey and collect the GCPs which can be very time consuming and/or hazardous. A potential solution lies with the recent introduction of lower cost rotary-winged drones fitted with higher accuracy on-board RTK GPS sensors. These have raised the possibility of conducting UAV surveys with the use of very few or no GCPs across the survey site, saving time and removing the need to access all areas for GCP placement.To test this possibility, we flew a 250 metre reach of the River Teme (max depth ~1m) on the English-Welsh border at 40m in July 2019 with two drones, i.e. a DJI Phantom 4 RTK UAV and base station and a DJI Phantom 4 PRO (non-rtk). The Phantom 4 RTK UAV was flown three times, i) using the flight program&#8217;s 2D option (nadir only and one flight path) ii) using the 3D option (camera angled at 60&#176; and flown in two directions) and iii) using the RTK off option and then using post-processing (PPK) to correct the image locations. 20 GCPs were placed across the site and their locations surveyed with a Trimble R8 dGPS and an additional 20 Independent Validation Points (IVPs) were surveyed along the floodplain for terrestrial validation points and 100 points within the channel were surveyed submerged area validation points.Imagery was processed with Agisoft Metashape (v1.5.5). A total of 28 DEMs were produced using the imagery from the two drones, different flight paths and different combinations of numbers and location of GCPs. These included reducing the number of GCPs from 20, to 10, 5, 3, 1 and 0. When using three GCPs, DEMs were produced by having them i) spread throughout the reach and ii) clustered close to one another. The bed heights of the submerged locations were corrected using the simple refraction correction first used by Westaway et al (2001) and then compared to the measured heights in the field. Accuracy was quantified using linear regression.The results of this analysis demonstrated the ability to obtain accurate surveys of bathymetry in depths upto 1m using a DJI Phantom 4 RTK UAV and base station and a significantly reduced number of GCPS, combined with the application of refraction correction. This study confirms that considerable time saving in terms of fieldwork can be gained from the use of an RTK rotary-winged drone and base station. This technology can also be beneficial for obtaining accurate survey data in locations where it may be unsafe or impossible to place GCPs due to the hazardous nature of the terrain.

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Assessing the Accuracy of Ortho-image using Photogrammetric Unmanned Aerial System

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprsarchives-xli-b1-867-2016 ◽

2016 ◽

Vol XLI-B1 ◽

pp. 867-872 ◽

Cited By ~ 3

Author(s):

H. H. Jeong ◽

J. W. Park ◽

J. S. Kim ◽

C. U. Choi

Keyword(s):

Camera Calibration ◽

Low Cost ◽

Control Point ◽

Image Data ◽

Ground Control ◽

Target Area ◽

Smart Camera ◽

Ground Control Point ◽

Time Basis ◽

Elevation Model

Smart-camera can not only be operated under network environment anytime and any place but also cost less than the existing photogrammetric UAV since it provides high-resolution image, 3D location and attitude data on a real-time basis from a variety of built-in sensors. This study’s proposed UAV photogrammetric method, low-cost UAV and smart camera were used. The elements of interior orientation were acquired through camera calibration. The image triangulation was conducted in accordance with presence or absence of consideration of the interior orientation (IO) parameters determined by camera calibration, The Digital Elevation Model (DEM) was constructed using the image data photographed at the target area and the results of the ground control point survey. This study also analyzes the proposed method’s application possibility by comparing a Ortho-image the results of the ground control point survey. Considering these study findings, it is suggested that smartphone is very feasible as a payload for UAV system. It is also expected that smartphone may be loaded onto existing UAV playing direct or indirect roles significantly.

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Deceptive Targets Generation Simulation Against Multichannel SAR

Electronics ◽

10.3390/electronics9040597 ◽

2020 ◽

Vol 9 (4) ◽

pp. 597

Author(s):

Penghui Ji ◽

Shiqi Xing ◽

Dahai Dai ◽

Bo Pang

Keyword(s):

Synthetic Aperture ◽

Minimum Condition ◽

Complex Coefficient ◽

Sar Images ◽

Digital Elevation ◽

Deceptive Jamming ◽

Elevation Model ◽

Interferometric Sar ◽

General Architecture ◽

Ground Moving Target Indication

Traditional synthetic aperture radar (SAR) deceptive jamming can effectively generate deceptive scenes or false targets in SAR images. However, these false targets or scenes can be easily distinguished or eliminated by the multichannel SAR system. To interfere with the multichannel SAR, we first analyzed the results of SAR deceptive jamming generated by one transponder and two transponders against three-channel SAR- ground moving target indication (GMTI). Then, we propose a new deceptive jamming method against three-channel SAR-GMTI by using three synergetic transponders. By modulating each transponder with a complex coefficient, three synergetic transponders can generate false moving targets with the controllable radial velocity and located azimuth position in three-channel SAR-GMTI. Besides, in this paper, we also introduce an algorithm to deploy three transponders reasonably by utilizing the minimum condition number. In the end, a general architecture of multiple transponders deceiving multichannel SAR is given. The proposed method can not only generate deceptive false targets against multichannel SAR-GMTI, but also guide the production of a deceptive digital elevation model (DEM) against multichannel interferometric SAR (InSAR). Simulations verify the effectiveness of the proposed method.

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High-Resolution Elevation Model of Lop Nur Playa Derived from TanDEM-X

Journal of Sensors ◽

10.1155/2019/6839703 ◽

2019 ◽

Vol 2019 ◽

pp. 1-12

Author(s):

Yuyang Geng ◽

Yun Shao ◽

Tingting Zhang ◽

Huaze Gong ◽

Lan Yang

Keyword(s):

High Resolution ◽

Least Square ◽

Synthetic Aperture ◽

Interferometric Synthetic Aperture Radar ◽

Relative Height ◽

Laser Altimeter ◽

Ice Cloud ◽

Digital Elevation ◽

Lop Nur ◽

Elevation Model

In this paper, a digital elevation model (DEM) was produced for Lop Nur playa produced with the data from TanDEM-X mission. The spatial resolution is 10 m. It covers an area of 38,000 km2 for orthometric height from 785 m to 900 m above sea level, which is composed of 42 interferometric synthetic aperture radar (InSAR) scenes. A least-square adjustment approach was used to reduce the systematic errors in each DEM scene. The DEM produced was validated with data from other sensors including Ice, Cloud, and land Elevation Satellite (ICESat) Geoscience Laser Altimeter System (GLAS) and aerial Structure-from-Motion (SfM) DEM. The results show that global elevation root mean square error to GLAS is 0.57 m, and the relative height error to SfM DEM in complicated terrain is 3 m. The excellent height reliability of TanDEM InSAR DEM in Lop region was proved in this paper. A reliable high-resolution basic topographic dataset for researches of Lop Nur was provided.

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InSAR Baseline Estimation for Gaofen-3 Real-Time DEM Generation

10.20944/preprints201806.0447.v1 ◽

2018 ◽

Author(s):

Huan Lu ◽

Zhiyong Suo ◽

Zhenfang Li ◽

Jinwei Xie ◽

Qingjun Zhang

Keyword(s):

Real Time ◽

Estimation Method ◽

Shuttle Radar Topography Mission ◽

The Real ◽

Digital Elevation ◽

Orbit Fitting ◽

Elevation Model ◽

Interferometric Sar ◽

Baseline Estimation ◽

Baseline Error

For Interferometry Synthetic Aperture Radar (InSAR), the normal baseline is one of the main factors that affect the accuracy of the ground elevation. For Gaofen-3 (GF-3) InSAR processing, the poor accuracy of the real-time orbit determination resulting in a large baseline error, leads to the modulation error in azimuth and the slope error in range for timely Digital Elevation Model (DEM) generation. In order to address this problem, a baseline estimation method based on external DEM is proposed in this paper. Firstly, according to the characteristic of the real-time orbit of GF-3 images, orbit fitting is executed to remove the non-linear error factor. Secondly, the height errors are obtained in slant-range plane between Shuttle Radar Topography Mission (SRTM) DEM and the GF-3 generated DEM after orbit fitting. At the same time, the height errors are used to estimate the baseline error which has a linear variation. In this way, the orbit error can be calibrated by the estimated baseline error. Finally, DEM generation is performed by using the modified baseline and orbit. This procedure is implemented iteratively to achieve a higher accuracy DEM. Based on the results of GF-3 interferometric SAR data for Hebei, the effectiveness of the proposed algorithm is verified and the accuracy of GF-3 real-time DEM products can be improved extensively.

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EVALUASI KETELITIAN HASIL ORTHOREKTIFIKASI CITRA SATELIT RESOLUSI TINGGI MENGGUNAKAN DEM STEREO-PAIR PLEIADES

Seminar Nasional Geomatika ◽

10.24895/sng.2018.3-0.923 ◽

2019 ◽

Vol 3 ◽

pp. 11

Author(s):

Diaz Cahya Kusuma Yuwana ◽

Maundri Prihanggo ◽

Agung Syetiawan

Keyword(s):

Sea Level ◽

Digital Elevation Model ◽

Control Point ◽

Ground Control ◽

Stereo Pair ◽

Check Point ◽

Mean Sea Level ◽

Rational Polynomial ◽

Digital Elevation ◽

Elevation Model

Implementasi proses orthorektifikasi membutuhkan data Digital Elevation Model (DEM) yang akurat. Ketersediaan data DEM yang akurat menjadi permasalahan tersendiri dalam proses orthorektifikasi. DEM hasil proses stereo-pair citra satelit pleiades menjadi sebuah alternatif. Penelitian ini berfokus untuk mengkaji ketelitian geometrik hasil orthorektifikasi dengan masukan DEM hasil stereo-pair (1m) citra satelit plaiades dengan DEM IFSAR (5m). Data yang digunakan meliputi sepasang Citra Satelit Pleiades, data hasil pengukuran GPS sebanyak 23 titik yang nantinya 11 titik dijadikan sebagai Ground Control Point (GCP) dan 12 titik dijadikan sebagai Independent Check Point (ICP), dan data DEM Ifsar 5 meter. Penelitian ini mendasarkan pada perbandingan ketelitian geometrik antara citra hasil othorektifikasi menggunakan masukan DEM IFSAR 5 m dengan masukan DEM dari hasil proses stereo-pair dua pasang citra satelit pleiades. Metode rational polynomial coefficient (RPC) digunakan untuk mendapatkan pembentukan epipolar citra dan citra ortho. DEM hasil stereo-pair citra satelit plaiades memiliki rentang -37 meter sampai dengan 155 meter di atas mean sea level (MSL). DEM hasil stereo-pair jauh lebih detail dari DEM IFSAR, kondisi perumahan dan jalan raya terepresentasikan lebih baik dan lebih jelas. Akurasi pada citra hasil orthorektifikasi menggunkan DEM stereo-pair 1 m adalah 1,04019 lebih baik dari hasil ortho menggunakan DEM IFSAR 5 m yaitu 1,12783. Perbedaan resolusi DEM sebesar 4 meter tidak signifikan mempengaruhi hasil orthorektifikasi citra satelit resolusi tinggi. Secara keseluruhan hasil akhir yang didapat dari kedua citra ortho dengan masukan data DEM tersebut masuk dalam ketelitian peta skala 1:5000 kelas 2 CE90.

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