Map Verification Research Articles

A-posteriori analysis of the performance of a rockfall susceptibility map

BackgroundRockfalls pose a serious threat along the main road network, representing a major hazard in mountainous territory and causing damage and victims. Currently, susceptibility mapping represents a starting point to identify areas more susceptible to rockfall occurrence, a key approach in land use planning and risk management. Despite the extensive use of these maps by decision makers and administrators, the usability of such maps over time and their reliability represent a poorly discussed and examined feature.MethodsHere, we proposed a-posteriori analysis of a three-year-old rockfall susceptibility map, generated along the main road network of the Aosta Valley, an alpine region of north-western Italy. To verify map consistency over time, we implemented a dual-analysis in GIS-environment and by text mining, to respectively analyse the geocoded data and textual information derivable from the regional landslide inventory. The first one allowed us to extract rockfall events occurred after the susceptibility map generation. By this way, we operated to spatially and temporally verify the map consistency. Jointly, the textual information reported in the Event Description Form, linked to each geocoded event, are being exploited. This allowed us to derive relevant information about occurred damage and their degree, presence of protective measures or secondary roads, i.e. involvement of, farm or forestry, road.ResultsThe implemented approach allowed us to prove the quality of the previous map in terms of reliability, robustness and degree of fitting respect to the succession of rockfall occurrence over time. After only three years as many as 198 rockfall events have been occurred and collected since the map was generated. Particularly, 80% of rockfall fit with “high” and “very high” susceptibility classes, and pointed out large involvement of main roads in rockfall occurrence, representing the most affected target with damage to road pavement and vehicles, as well as a relevant involvement of existing rockfall barriers and of the dense network of forestry roads and footpaths that characterize this alpine region.ResultsThe proposed approach representing a starting point in landslide susceptibility map verification and usability as valid instrument for a reliable land planning.

THE BASIC PROBLEMS AND COUNTERMEASURES OF MAP INSPECTION

Abstract. Map verification plays a crucial role in ensuring the accuracy and reliability of map data, which in turn establishes the foundation for map transparency. In China, the number of approved map inspections has been increasing annually, with a diverse range of map products being applied for inspection. Taking the example of the 'number of maps accepted for inspection' by the Ministry of Natural Resources of the People’s Republic of China, there has been a consistent upward trend in the number of accepted inspections. From 2017 to 2021, the average annual growth rate of accepted inspections exceeds 18.85%. Not only are new types, uses, and formats of map products emerging, but there is also an increase in the utilization of electronic global maps. However, challenges such as the inefficient information transfer during the inspection application process and the limited automation of technical inspections persist. Furthermore, issues related to the variability of inspection results based on individual experiences need to be addressed. To tackle these problems, this paper proposes a comprehensive technical framework for map verification based on the principles of "data sharing, business collaboration, and intelligent assistance". The objective is to establish a map verification service mechanism that promotes cross-departmental coordination and intelligent cooperation. Implementing this framework will facilitate the smooth operation of national map verification services and expedite the sharing and openness of geospatial data.

Historical maps confirm the accuracy of zero‐inflated model predictions of ancient tree abundance in English wood‐pastures

Abstract Ancient trees have important ecological, historical and social connections, and are a key source of dead and decaying wood, a globally declining resource. Wood‐pastures, which combine livestock grazing, open spaces and scattered trees, are significant reservoirs of ancient trees, yet information about their true abundance within wood‐pastures is limited. England has extensive databases of both ancient trees and wood‐pasture habitat, providing a unique opportunity for the first large‐scale, national case study to address this knowledge gap. We investigated the relationship between the abundance of ancient trees in a large sample of English wood‐pastures (5,571) and various unique environmental, historical and anthropogenic predictors, to identify wood‐pastures with high numbers of undiscovered ancient trees. A major challenge in many modelling studies is obtaining independent data for model verification: here we introduce a novel model verification step using series of historic maps with detailed records of trees to validate our model predictions. This desk‐based method enables rapid verification of model predictions using completely independent data across a large geographical area, without the need for, or limitations associated with, extensive field surveys. Historic map verification estimates correlated well with model predictions of tree abundance. Model predictions suggest there are ~101,400 undiscovered ancient trees in all wood‐pastures in England, around 10 times the total current number of ancient tree records. Important predictors of ancient tree abundance included wood‐pasture area, distance to several features including cities, commons, historic Royal forests and Tudor deer parks, and different types of soil and land classes. Synthesis and applications. Historical maps and statistical models can be used in combination to produce accurate predictions of ancient tree abundance in wood‐pastures, and inform future targeted surveys of wood‐pasture habitat, with a focus on those deemed to have undiscovered ancient trees. This study provides support for improvements to conservation policy and protection measures for ancient trees and wood‐pastures.

Диагностика и картографирование Местообитаний южных тундр (на примере ключевого участка р. Шапкина)

A classification of habitats is given for the area studied on the right bank of the Shapkina River, (East European tundra, southern subzone). The classification is based on the topographic position of biotopes and their plant communities. The mosaic of tundra vegetation makes it difficult for mapping. Usually in nature the combinations of plant communities are confined to specific types of habitats. To display the regularities of a fine-contour vegetation cover on maps, we used the habitat approach diagnosed by combinations of plant communities. The field survey was done in the summer of 2020; total area of about 150 km2 was surveyed. Ultra-high resolution (3–5 cm/px) aerial photography was carried out for key areas, using a DJI Mavic Pro Platinum quadrocopter (shooting height from 80 to 200 m). 25 geobotanical relevés were completed; in addition 180 short descriptions were made for map verification. All types of habitats in the proposed scheme are correlated with EUNIS units, lists of syntaxa are given. A large-scale map (1 : 50 000) of habitats was prepared. All tundra habitats are divided into two groups. First level of habitat classification confined to the main landscape types: watersheds and river valleys of watercourses with a floodplain regime. Watershed habitats are subdivided into 5 categories (second level of habitat classification), determined by their runoff-geochemical position on the generalized geomorphological profile (from the highest relief elements to the lowest ones), including underlying rocks, moisture regime and migration of elements, exposure features. Due to the small amount of data mapping of river valley habitats was performed only for units of the second level. At the third level watershed habitats are well diagnosed by vegetation at the level of associations, combinations of commuities, soil cover, and microrelief. As a result, most units of the second and third levels are clearly distinguished on aerial photography obtained using a quadrocopter, and also correlate with specific syntaxa. As a result of field data and aerial photographs analyses, 12 categories of habitats, represented by 17 syntaxa, were identified for watersheds at the 3rd level.

GIS-Based Landslide Susceptibility Map Verification by its Geotechnical and Geological Characteristics

The famous 2006 Laplae rainfall-triggered landslide has caused hundreds of million Baht lost. The objective of this paper is to evaluate and to compare present geotechnical and geological conditions between the landslide area and landslide-free area to verify a landslide susceptibility map. Detailed field surveys acquired 14 samples: undisturbed, disturbed soils as well as rocks. Sensitivity and back-analysis were also performed. 35.44% of landslides occurred in meta-shale - greywacke-interbedding Formation, and another 64.56% happened in meta-greywacke - basaltic andesite Formation. The dominant slope of the landslide is in 300-400 slope, with aspects toward South direction, and in a range of <1,000 meters from geological structures. Landslide area is distinguished from the non-landslide area by its various grades of materials, lower quartz content, higher clay content, finer composition of parental rocks and soils, higher average ratio of smectite versus quartz, lower compressive strength, lower shear strength, lower angle of internal friction, lower cohesion value, more poorly graded, higher soil moisture, higher liquid limit and plasticity index, and factor of safety is generally less than 1. The result of the sensitivity analysis indicated that in a failure condition, the cohesion and angle of internal friction angle values are equal to 2.51 kPa and 13.700, respectively. However, the results of laboratory tests showed that the cohesion and angle of internal friction values are equal to 8.59 kPa and 14.20. These results verified the landslide susceptibility map that the high landslide susceptibility area has the engineering characteristics of the landslide-prone area, while the low susceptible one has the characteristics of the non-landslide area.

SU‐F‐T‐522: Dosimetric Study of Junction Dose in Double Isocenter Flatten and Flatten Filter Free IMRT and VMAT Plan Delivery

Purpose:To quantify the dosimetric accuracy of junction dose in double isocenter flattened and flatten filter free(FFF) intensity modulated radiation therapy(IMRT) and volumetric modulated arc therapy(VMAT) plan delivery using pelvis phantom.Methods:Five large field pelvis patients were selected for this study. Double isocenter IMRT and VMAT treatment plans were generated in Eclipse Treatment planning System (V.11.0) using 6MV FB and FFF beams. For all the plans same distance 17.0cm was kept between one isocenter to another isocenter. IMRT Plans were made with 7 coplanar fields and VMAT plans were made with full double arcs. Dose calculation was performed using AAA algorithms with dose grid size of 0.25 cm. Verification plans were calculated on Scanditronix Wellhofer pelvis slab phantom. Measurement point was selected and calculated, where two isocenter plan fields are overlapping, this measurement point was kept at distance 8.5cm from both isocenter. The plans were delivered using Varian TrueBeamTM machine on pelvis slab phantom. Point dose measurements was carried out using CC13 ion chamber volume of 0.13cm3.Results:The measured junction point dose are compared with TPS calculated dose. The mean difference observed was 4.5%, 6.0%, 4.0% and 7.0% for IMRT‐FB,IMRT‐FFF, VMAT‐FB and VMAT‐FFF respectively. The measured dose results shows closer agreement with calculated dose in Flatten beam planning in both IMRT and VMAT, whereas in FFF beam plan dose difference are more compared with flatten beam plan.Conclusion:Dosimetry accuracy of Large Field junction dose difference was found less in Flatten beam compared with FFF beam plan delivery. Even though more dosimetric studies are required to analyse junction dose for FFF beam planning using multiple point dose measurements and fluence map verification in field junction area.

Pemanfaatan citra ASTER dalam penentuan dan verifikasi daerah rawan Demam Berdarah Dengue (DBD) di Kota Banjar Provinsi Jawa Barat

Distribution of Dengue Hemorrhagic Fever (DHF) can be viewed from geospatial perspective elaborating temperature, rain fall, humidity, and certain land uses information. Remote sensing and GIS approach can be used as effective tool on dengue prevention and control policies. The aim of this study was to identify vulnerable dengue areas in Banjar, West Java through image verification. This study is an observational study with cross sectional analysis conducted in Banjar in March to October 2012 with a sample from the entire population suffering from dengue at all ages as well as environmental conditions. As for the single sample larvae method. Results showed that the area of DF high vulnerability zones in Banjar was 18.29%,, moderate zone (63.45%) and less vulnerable zone (18.27%). The map verification was done high and moderate vulnerability zones were classified into dengue-prone classes, while low vulnerability zone was grouped into dengue-free zone. In conclusion, the accuracy was reached 94.74% and it was indicated that dengue cases was mostly spreaded in dengue-prone areas. Keywords: geographic information system, remote sensing, dengue fever, Banjar city, ASTER

Poster — Thur Eve — 61: Intensity Modulated Radiation Therapy: The Relationship between Planar Dose Map Verification and Dosimetric Outcome

This work analyses the consequences of random and systematic dose differences in the comparison of calculated against measured planar dose distributions for IMRT from the perspective of a surrogate of the treatment outcome: Equivalent Uniform Dose (EUD). In‐house software was developed to incorporate normally distributed errors in the fluence maps of 3 head and neck (H&amp;N) and 3 prostate plans and simulate dose differences that appear randomly across the planar dose maps. The plans with random errors were grouped according to the following passing rates: 1) 90–95%, 2)85–90% and 3)80–85% during patient specific quality control. The passing criteria included a 3% absolute dose, 3 mm distance to agreement (DTA), and a minimum dose difference of 2 cGy. A systematic 1% dose error could also be incorporated by altering the MUs of each plan with random errors. The impact of random errors on the prescribed EUDs of H&amp;N plans ranged from −2.7 to −1.3% for the CTV and −1.0 to 0.6 Gy for the OARs while in prostate plans they ranged from −1.6 to −0.6% for the CTV and −1.2 to −0.4 Gy for the OARs over the range examined. The criterion of 90% passing rate for 3% absolute dose and 3 mm DTA kept the effects of random errors within a dosimetric goal of 2% change in prescribed EUDs of the targets and 2 Gy for the OARs. Systematic errors, if present, may cause larger effects on clinical dosimetry while still meeting patient specific quality control tolerances.

SU‐DD‐A1‐04: In Vivo Prostate IMRT Dosimetry With MOSFET Detectors Using Brass Build‐Up Caps

Purpose: To develop a general formalism with various correction factors to predict dmax entrance dose with the new hemispherical brass buildup caps to be used with MOSFET detectors in anterior prostate IMRT fields and thereby integrate in vivo IMRT dose measurement as part of routine QA process in IMRT radiotherapy Method and Materials: We have used the new wide energy hemispherical build‐up caps for this study. Due to its high density and high atomic number it provides the minimal amount of metal needed to achieve full build‐up at Dmax for a range of photon energies. We have developed a general formalism to predict Dmax entrance dose by applying necessary correction factors after studying the response of MOSFET with brass build up caps for energy, dose rate, dose reproducibility, SSD and patient specific IMRT correction factor. Results: In vivo Prostate IMRT dose measurements with MOSFET detectors using brass buildup caps was performed and compared against dose predicted by two different treatment planning systems. We used both 6 MV and 10 MV for this study and compared the in vivo MOSFET detector reading with dose predicted by Philips Pinnacle (6 MV) and CMS XiO (10 MV) treatment planning systems respectively. We achieved a overall accuracy of better than ± 5% on measured patient doses. Conclusion: Routine IMRT QA in most institutions today only involves verifying the optimized fluence map delivered to the patient in a test phantom at a certain preset depth. Based on our work here, we believe adding in vivo IMRT dosimetry with MOSFET detectors using the new brass build up caps along with routine fluence map verification in phantoms and MLC quality assurance offers greater accuracy and confidence in actual dose delivered to the patient.

SU‐FF‐T‐291: Intensity Map Verification for IMRT QA Using An A‐Si EPID

Purpose: To use a flat panel electronic portal imaging device (EPID) for intensity map verification as part of an intensity modulated radiation therapy (IMRT) QA program. Method and Materials: An a‐Si EPID was used to image each field shape segment of a head and neck IMRT treatment. The DICOM images produced from each gantry angle were summed together and weighted according to the number of MU measured. Open field portal images were acquired at the end of the treatment, for each gantry angle, and subtracted from each composite image. A GUI was created in the MATLAB environment to read and sort each image according to gantry angle and MU measured, perform the image summations/subtractions, produce and display a final composite image. Results: Subtraction of the open field portal image from the field shape composite image removed the anatomy from the treatment area and produced a true intensity map. Outside of the treatment area the anatomy was visible, thus providing verification of correct radiation delivery location. The composite images were compared to other composite images produced using the same treatment plan delivered with and without a phantom and were found to be in excellent agreement. The images were also compared to the intensity map images created in the treatment planning system. Imaging of each segment of an IMRT treatment required no additional radiation be delivered to the patient. The open field portal images require additional radiation, however each image needs only to be acquired once during a course of treatment. Conclusion: This work indicates that flat panel EPIDs may be used to image an IMRT treatment and accurately and efficiently verify the intensity and location of the delivered radiation. Future investigations will use the 2D images to produce a 3D intensity “cloud” image.

Efficient multipoint mapping: making use of dominant repulsion-phase markers.

The paper is devoted to the problem of multipoint gene ordering with a particular focus on "dominance" complication that acts differently in conditions of coupling-phase and repulsion-phase markers. To solve the problem we split the dataset into two complementary subsets each containing shared codominant markers and dominant markers in the coupling-phase only. Multilocus ordering in the proposed algorithm is based on pairwise recombination frequencies and using the well-known travelling salesman problem (TSP) formalization. To obtain accurate results, we developed a multiphase algorithm that includes synchronized-marker ordering of two subsets assisted by re-sampling-based map verification, combining the resulting maps into an integrated map followed by verification of the integrated map. A new synchronized Evolution-Strategy discrete optimization algorithm was developed here for the proposed multilocus ordering approach in which common codominant markers facilitate stabilization of the marker order of the two complementary maps. High performance of the employed algorithm allows systematic treatment for the problem of verification of the obtained multilocus orders, based on computing-intensive bootstrap and jackknife technologies for detection and removing unreliable marker scores. The efficiency of the proposed algorithm was demonstrated on simulated and real data.

Robot Map Verification of a Graph World

In the map verification problem, a robot is given a (possibly incorrect) map M of the world G with its position and orientation indicated on the map. The task is to find out whether this map, for the given robot position and its orientation in the map, is correct for the world G. We consider the world model of a graph G = (V G, E G) in which, for each vertex, edges incident to the vertex are ordered cyclically around that vertex. (This also holds for the map M = (V M, E M.) The robot can traverse edges and enumerate edges incident on the current vertex, but it cannot distinguish vertices (and edges) from each other. To solve the verification problem, the robot uses a portable edge marker, that it can put down at an edge of the graph world G and pick up later as needed. The robot can recognize the edge marker when it encounters it in the world G. By reducing the verification problem to an exploration problem, verification can be completed in O(|V G| × |E G|) edge traversals (the mechanical cost) with the help of a single vertex marker which can be dropped and picked up at vertices of the graph world (G. Dudek, M. Jenkin, E. Milios, and D. Wilkes, IEEE Trans. on Robotics and Automation, vol. 7, pp. 859–865, 1991; Robotics and Autonomous Systems, vol. 22(2), pp. 159–178, 1997). In this paper, we show a strategy that verifies a map in O(|V M|) edge traversals only, using a single edge marker, when M is a plane embedded graph, even though G may not be planar (e.g., G may contain overpasses, tunnels, etc.).

THE NEED FOR CONTROLLED INFORMATION PROCESSING IN THE VISUAL ACQUISITION OF ROUTE KNOWLEDGE

The route knowledge of participants who performed a concurrent task during a simulated route-learning exercise was compared to that of participants engaged only in the route-learning exercise by employing tests of scene recognition, distance estimation and map verification. Results indicated performance decrements on the scene recognition and distance estimation tasks on the part of participants in the concurrent task condition, thus supporting the interpretation that these tasks were sensitive to the reduction in available attentional resources. Performance on the map verification task was generally poor, a fact that may have masked the general effect of the concurrent task manipulation. Comparisons involving only those subgroups for which performance was above chance level provided evidence that this task was also sensitive to the availability of resources. In addition, results from the map verification task clearly pointed to map orientation as an important factor influencing the ability to recognize a cartographic representation of a path of movement within a large-scale environment.