Geometric Accuracy Assessment of Very High-Resolution Optical Data Orthorectified using TerraSAR-X DSM to Support Disaster Management in Indonesia

2018 ◽  
Vol 8 (6) ◽  
pp. 2450
Author(s):  
Inggit Lolita Sari ◽  
Sukentyas Estuti Siwi ◽  
Randy Prima Brahmantara ◽  
Haris Suka Dyatmika ◽  
Agus Suprijanto ◽  
...  
Keyword(s):  
High Resolution ◽  
Disaster Management ◽  
Accuracy Assessment ◽  
Optical Data ◽  
Geometric Accuracy ◽  
Very High

scholarly journals Automatic Positional Accuracy Assessment of Imagery Segmentation Processes: A Case Study

2021 ◽  
Vol 10 (7) ◽  
pp. 430
Author(s):  
Juan J. Ruiz-Lendínez ◽  
Manuel A. Ureña-Cámara ◽  
José L. Mesa-Mingorance ◽  
Francisco J. Quesada-Real
Keyword(s):  
High Resolution ◽  
Quality Assessment ◽  
Accuracy Assessment ◽  
Geographic Information ◽  
Aerial Image ◽  
Positional Accuracy ◽  
Key Aspects ◽  
Very High ◽  
The Ideal

There are many studies related to Imagery Segmentation (IS) in the field of Geographic Information (GI). However, none of them address the assessment of IS results from a positional perspective. In a field in which the positional aspect is critical, it seems reasonable to think that the quality associated with this aspect must be controlled. This paper presents an automatic positional accuracy assessment (PAA) method for assessing this quality component of the regions obtained by means of the application of a textural segmentation algorithm to a Very High Resolution (VHR) aerial image. This method is based on the comparison between the ideal segmentation and the computed segmentation by counting their differences. Therefore, it has the same conceptual principles as the automatic procedures used in the evaluation of the GI´s positional accuracy. As in any PAA method, there are two key aspects related to the sample that were addressed: (i) its size—specifically, its influence on the uncertainty of the estimated accuracy values—and (ii) its categorization. Although the results obtained must be taken with caution, they made it clear that automatic PAA procedures, which are mainly applied to carry out the positional quality assessment of cartography, are valid for assessing the positional accuracy reached using other types of processes. Such is the case of the IS process presented in this study.

Reference Data and Methods for Validation of Very High Resolution Optical Data Within ESA / EDAP Project

2021 ◽  
Author(s):  
Sébastien Saunier
Keyword(s):  
High Resolution ◽  
Image Quality ◽  
Spatial Resolution ◽  
Reference Data ◽  
Test Site ◽  
Optical Data ◽  
Surface Model ◽  
Landsat 8 ◽  
Validation Process ◽  
Very High

<p>In this paper, the authors propose to describe the methodologies developed for the validation of Very High-Resolution (VHR) optical missions within the Earthnet Data Assessment Pilot (EDAP) Framework.  The use of surface-based, drone, airborne, and/or space-based observations to build calibration reference is playing a fundamental role in the validation process. A rigorous validation process must compare mission data products with independent reference data suitable for the satellite measurements. As a consequence, one background activity within EDAP is the collection, the consolidation of reference data of various nature depending on the validation methodology.</p><p>The validation methodologies are conventionally divided into three categories; i.e. validations of the measurement, the geometry and the image quality. The validation of the measurement requires an absolute calibration reference. This latter on is built up by using either in situ measurements collected with RadCalNet[1] stations or by using space based observations performed with “gold” mission (Sentinel-2, Landsat-8) over Pseudo Invariant Calibration Site (PICS). For the geometric validation, several test sites have been set up. A test site is equipped with data from different reference sources. The full usability of a test site is not systematic. It depends on the validation metrics and the specifications of the sensor, particularly the spatial resolution and image acquisition geometry. Some existing geometric sites are equipped with Ground Control Point (GCP) set surveyed by using Global Navigation Satellite System (GNSS) devices in the field.  In some cases, the GCP set comes in support to the refinement of an image observed with drones in order to produce a raster reference, subsequently used to validate the internal geometry of images under assessment. Besides, a limiting factor in the usage of VHR optical ortho-rectified data is the accuracy of the Digital Surface Model (DSM) / Digital Terrain Model (DTM). In order to separate errors due to terrain elevation and error due to the sensor itself, some test sites are also equipped with very accurate Light Detection and Ranging (LIDAR) data.</p><p>The validation of image quality address all aspect related to the spatial resolution and is strongly linked to both the measurement and the geometry. The image quality assessments are performed with both qualitative and quantitative approaches. The quantitative approach relies on the analysis of artificial ground target images and lead to the estimate of Modulation Transfer Function (MTF) together with additional image quality parameters such as Signal to Noise Ratio (SNR). On the other hand, the qualitative approach assesses the interpretability of input images and leads to a rating scaling[2] which is strongly related to the sensor Ground Resolution Distance (GRD). This visual inspection task required a database including very detailed image of man-made objects. This database is considered within EDAP as a reference.</p><div> <div> <p>[1] https://www.radcalnet.org</p> </div> <div> <p>[2] https://fas.org/irp/imint/niirs.htm</p> </div> </div>

Disastrous landslides under changing forcing factors triggered end 2019 in West Kenya

2020 ◽  
Author(s):  
Romy Schlögel ◽  
Samir Belabbes ◽  
Luca Dell Oro ◽  
Aline Déprez ◽  
Jean-Philippe Malet
Keyword(s):  
High Resolution ◽  
Heavy Rain ◽  
Detection Algorithm ◽  
Optical Data ◽  
African Countries ◽  
International Space ◽  
Landslide Occurrence ◽  
Rapid Mapping ◽  
West Pokot ◽  
Very High

<p>End of 2019 was particularly damaging in some Central and Eastern African countries due to the heavy rain which triggered numerous mass movements. Extremely heavy rainfall were recorded in Pokot South and Sigor Sub counties located in West Pokot County (Kenya) on 23 and 24 November 2019. An official from the West Pokot county government said 53 people died after devastating rains caused huge landslides in this County while several roads in the valley have been affected and at least 5 bridges were reported as destroyed. Indeed Kenya has seen several villages heavily affected by landslides after floods and torrential rain. These movements were detected from a combination of high-resolution Sentinel 2 images and very high-resolution Pléiades-1 images acquired before and after the landslide catastrophe with the engagement of the UNOSAT’s rapid mapping service which activated the International space charter mechanism. In the following days, a series of analysis of the affected zones from very high-resolution optical data were delivered in the following days to UNOSAT and the emergency response authorities in Kenya. This study explains the mechanism of the rapid mapping activation and the use of the Disaster Charter mechanism to help to detect the extent of the phenomena and impacted infrastructure by providing a rapid mapping related analysis, conducted at UNOSAT with satellite data provided by space agencies involved in the International Space Charter. Science-driven landslide inventories were created with the ALADIM change detection algorithm integrated on the ESA GeoHazards Exploitaton Platform. Over the studied region of 400 km<sup>2</sup>, nearly 6000 landslides were detected, corresponding to an affected area of ca. 18 km<sup>2</sup>. Then, the triggering factors of this disaster were analysed understanding how changing raining conditions is affecting the area while it was not considered as landslides-prone. This research aims to state if this particular event is considered as abnormal according to rainfall trends and landslide occurrence looking at long time series and/or human practices play a major role in triggering this type of catastrophe.</p>

Change detection in very high resolution imagery and vector data applied to the monitoring of geographical conditions

Sensor Review ◽  
2016 ◽  
Vol 36 (4) ◽  
pp. 347-358 ◽  
Author(s):  
Zhenzhen Zhao ◽  
Aiwen Lin ◽  
Qin Yan ◽  
Jiandi Feng
Keyword(s):  
High Resolution ◽  
Change Detection ◽  
Accuracy Assessment ◽  
Assessment Method ◽  
Chinese Government ◽  
Vector Data ◽  
Content Type ◽  
Image Objects ◽  
Object Based ◽  
Very High

Purpose Geographical conditions monitoring (GCM) has elicited significant concerns from the Chinese Government and is closely related to the “Digital China” program. This research aims to focus on object-based change detection (OBCD) methods integrating very-high-resolution (VHR) imagery and vector data for GCM. Design/methodology/approach The main content of this paper is as follows: a multi-resolution segmentation (MRS) algorithm is proposed for obtaining homogeneous and contiguous image objects in two phases; a post-classification comparison (PCC) method based on the nearest neighbor algorithm and an image-object analysis (IOA) technique based on a differential entropy algorithm are used to improve the accuracy of the change detection; and a vector object-based accuracy assessment method is proposed. Findings Results show that image objects obtained using the MRS algorithm attain the objectives of the “same spectrum within classes” and “different spectrum among classes”. Moreover, the two OBCD methods can detect over 85 per cent of the changed regions. The PCC strategy can obtain the categories of image objects with a high degree of precision. The IOA technique is easy to use and largely automated. Originality/value On the basis of the VHR satellite imagery and vector data, the above methods can effectively and accurately provide technical support for GCM implementation.

scholarly journals INFORMATION CONTENT ANALYSIS FROM VERY HIGH RESOLUTION OPTICAL SPACE IMAGERY FOR UPDATING SPATIAL DATABASE

2018 ◽  
Vol XLII-4 ◽  
pp. 25-31 ◽  
Author(s):  
M. Alkan
Keyword(s):  
High Resolution ◽  
Information Content ◽  
Satellite Image ◽  
Topographic Map ◽  
Geometric Accuracy ◽  
Space Images ◽  
Important Place ◽  
Sampling Distance ◽  
Map Scale ◽  
Very High

<p><strong>Abstract.</strong> High resolution satellite images started with IKONOS imagery. After the launch of the very high resolution IKONOS in the 1990s, a new generation of commercial Earth-imaging satellites have pioneered a new era of space imaging for observations of Earth. The IKONOS satellite image has an important place sampling range with 1<span class="thinspace"></span>m GSD. In the subsequent Quickbird satellite image, the GSD is down to 62<span class="thinspace"></span>cm and the sensitivity is even higher. Advancements in the geometric resolution of space images have improved the conditions for generations of large-scale topographic maps. With using WorldView-1, WorldView-2, and GeoEye-1, images can now be captured from space with a 0.5<span class="thinspace"></span>m ground sampling distance (GSD). The Worldview-4 display with the highest technology and resolution is being used in various application areas. WorldView-4 (formerly GeoEye-2), launched in November 2017, provides a second sensor which is capable of delivering imagery at 30<span class="thinspace"></span>cm resolution, the highest level of detail commercially available from satellite. WorldView-4 greatly expands the 30<span class="thinspace"></span>cm collection capabilities and archive growth in today’s imagery environment. Geometric accuracy and information content are the most significant components of mapping from space images. By using economical, rapid and periodic acquisition, and corresponding ground resolution, these satellites have established an alternative to aerial photos and have been widely used for various applications such as object extraction, change detection, topographic map production, and development of Geographic Information Systems (GIS). The utility of VHR images is dependent on their geometric accuracy and information content. Related with the study, the generally required production scale of 0.05 to 0.1<span class="thinspace"></span>mm GSD in the map scale has been confirmed. This corresponds to a topographic map scale of 1<span class="thinspace"></span>:<span class="thinspace"></span>10,000 respectively 1<span class="thinspace"></span>:<span class="thinspace"></span>5000 for 1<span class="thinspace"></span>m and 0.5<span class="thinspace"></span>m GSD images. In this study, images from IKONOS, QuickBird, WorldView-1, Worldview-2 and WorldView-4 have been used for topographic mapping. For this reason, İstanbul and Zonguldak test fields are an important area for applications of the high resolution imageries. The details which can be identified in the space images dominantly depends upon the ground resolution, available as ground sampling distance (GSD). In this study, high resolution imageries have been tested depending on the GSD and corresponding to the map scales for updating GIS database.</p>

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