Verification of ZY-3 Satellite Imagery Geometric Accuracy Without Ground Control Points

Large scale base map can be obtained by various methods, one of them is orthorectification process of remote sensing satellite imagery to eliminate the relief displacement caused by height variation of earth surface. To obtain a map images with good quality, it requires additional data such as sensor model in the form of rational polynomial coefficients (RPC), surface model data, and ground control points Satellite imageries with high resolution file size are relatively large. In order to process them, high specification of hardwares were required. To overcome this by cutting only a portion of the images, based on certain study areas were suffer from of georeference lost so it would not be able to orthorectified. On the other hand, in several remote sensing software such as ESA SNAP and Orfeo Toolbox (OTB) subset or pixel extraction from satellite imagery, preserve the imagery geometric sensor models. This research aimed at geometric accuracy of orthorectification carried out in a single scene of Pleiades Imagery within the Kepahiang Subdistrict, located at Kepahiang Regency, Bengkulu Province, by using DEMNAS and the imagery refined sensor mode, and ground control points taken using GPS Survey. Related with the raw imagery condition which consists of Panchromatic and multispectral bands, this study were separated to assembly, pan sharpening , and sensor model refinement stages prior to orthorectification carried out both in the original or full extent imagery and the result of subset extent imagery. After these processses taken place, we measure the accuracy of each full and subset imagery.These procedures were carried out using Orfeo toolbox 6.6.0 in the Linux Mint 19 Operating system. From the process log, running time in total were 7814.518 second for the full extent and 4321.95 seconds for the subset processess. And as a big data process, the total of full extent imageries was 83.15 GB while the subset size was only 30.73 GB. The relative accuracy of the full extent and its subset imagery were 0.431 meters. Accuracy of the sensor model refinement process are 1.217 meters and 1.550 meters with GCP added, while the accuracu of the orthorectifications results were 0.416 meters and 0.751 meters by using ICP. Variation of execution time may caused by the data input size and complexity of the mathematical process carried out in each stages. Meanwhile, the variation of accuracy may caused by the check or control points placements above satellite Imagery which suffer from uncertainty when dealing with the sub-pixel position or under 0.5 meters.

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THE OVERSEAS GEOMETRIC ACCURACY VALIDATION OF ZY-3 SATELLITES IMAGES

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

10.5194/isprs-archives-xliii-b3-2020-1403-2020 ◽

2020 ◽

Vol XLIII-B3-2020 ◽

pp. 1403-1410

Author(s):

Y. Xue ◽

X. Tang ◽

X. Gao ◽

Q. Yue ◽

W. Kainz ◽

...

Keyword(s):

Cloud Service ◽

Geographic Information ◽

Ground Control ◽

Accuracy Evaluation ◽

Control Points ◽

Geometric Accuracy ◽

Mountain Area ◽

Ground Control Points ◽

Information Updating ◽

Corrected Image

Abstract. With China’s first stereo imaging satellite ZY-3’s successful launch and two satellites networking operation, space remote sensing becomes an important means of data acquisition for survey and mapping, and geographic information updating in China.The updating period of 4D products in China is shortened by one third, the geographic information updating capability was improved more than 2 times.After more than eight years of stable and continued earth observation, ZY-3 statellites data coverage has gradually achieved more than half of the earth land which enables the overseas service for global geospatial application. Focusing on the Chinese domestic mapping applications and services, the data of ZY-3 and other domestic land observation satellites can be real-time pushed and distributed across China through the satellite cloud service platform, and worldwide for facilitating the "Belt and Road" initiative, which is promoted through the GEOSS as well for global application.This paper presents the overseas geometric accuracy evaluation and validation of ZY-3 satellites images, which was carried out systematically for the first time abroad and complements with China’s mapping evaluation practices to provide a comprehensive technical guidelines for global mapping application. The direct location accuracy of ZY-3 satellites sensor corrected image products were further evaluated and verified cooperating with the University of Vienna, Austria. The location deviations in mountain area and in flat area were analyzed and compared to check the deviation pattern and validate their consistency with the results in China.Utilizing China’s ZY-3 satellites images ranging from 2012–2018, the DSM was generated automatically based on a semiglobal optimization method (Yue et al. 2016) using self-developed software SDP without ground control points but using SRTM data as elevation reference to improve the geometric accuracy. The result shows the elevation accuracy of DSM is 3.19 m (RMSE), satisfying the local requirement for 10m interval contour mapping.The planar accuracy of DOM generated without ground control points utilizing ZY-3 satellites images within 2012–2015 is 2.46 m (RMSE). With 128 orthorectified aerial photo slots provided by NGD of Laos as reference, the planar accuracy of the DOM generated utilizing ZY-3 satellites images from 2016–2018 is 1.65 m (RMSE), which can satisfy the local 1:25000 planar accuracy requirement and overlay with the local 1:2000 transportation data exactly. The overseas geometric accuracy evaluation and validation of ZY-3 satellites images provides a systematic and practical guidance for future global applications by complementing with china’s experience, which would be beneficial to overseas users in acknowledging the usage of ZY-3 satellites data and help to promote it’s global applications.

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