BEGIN:VCALENDAR VERSION:2.0 PRODID:-//pretalx//talks.osgeo.org//foss4g-2026//talk//WAXYEY BEGIN:VTIMEZONE TZID:JST BEGIN:STANDARD DTSTART:20000101T000000 RRULE:FREQ=YEARLY;BYMONTH=1 TZNAME:JST TZOFFSETFROM:+0900 TZOFFSETTO:+0900 END:STANDARD END:VTIMEZONE BEGIN:VEVENT UID:pretalx-foss4g-2026-WAXYEY@talks.osgeo.org DTSTART;TZID=JST:20260902T140000 DTEND;TZID=JST:20260902T143000 DESCRIPTION:Biological invasions represent one of the most significant thre ats to global biodiversity and agricultural systems\, causing substantial ecological and economic damage worldwide. Among emerging invasive pests in East Asia\, Aromia bungii\, commonly known as the red-necked longhorn bee tle\, has become a serious threat in Japan. The species attacks several Pr unus species\, including ornamental cherry trees (Cerasus spp.)\, peach (P runus persica)\, and plum (Prunus salicina). Because cherry trees play an important ecological and cultural role in Japan\, the spread of this invas ive beetle has raised growing concerns for landscape management and biodiv ersity conservation.\nSince its first detection in Aichi Prefecture in 201 2\, A. bungii has expanded rapidly across urban and peri-urban areas. Unde rstanding its spatial pattern is therefore essential for effective monitor ing and early intervention. Spatial analysis can be applied to these proce sses. However\, such analyses fundamentally depend on how spatial data are defined\, including the geometry of the spatial grid\, which can influenc e the results.\nThus\, to examine how grid shape influences spatial analys is results\, this study evaluates spatial autocorrelation measures using d ifferent tessellations of invasive species occurrence data. Specifically\, we compared rectangular and hexagonal grids for analysing spatial pattern s in A. bungii occurrence records and density of rivers in Saitama Prefect ure\, Japan.\n\nVolunteer-based occurrence data for A. bungii were compile d from field surveys across Saitama Prefecture from 2017 to 2024\, yieldin g 2\,349 confirmed presence records. Records were classified as confirmed presences if either adult beetle observations (Adult-yes = 1) or evidence of tree damage (Tree_damage = 1) was recorded. All records were georeferen ced using latitude–longitude coordinates (WGS84) and then reprojected to UTM Zone 54N (EPSG:32654) to ensure metric accuracy in spatial calculatio ns. We assembled the occurrence data into predefined grid cells to explore spatial patterns across the study area and to enable consistent spatial a ggregation and neighbourhood-based analyses.\n\nTwo grid tessellation sche mes were constructed over the study area. The rectangular grid consisted o f 4\,013 cells at a 1 km × 1 km resolution. Each rectangular cell overlai d with the occurence point of location Aromia bungii presence in Saitama. This configuration corresponds to rook contiguity\, where only four direct ly adjacent neighbours are considered. To evaluate the effect of diagonal bias\, the same rectangular grid was also analysed using queen contiguity\ , which includes eight neighbouring cells by incorporating both direct and diagonal neighbours. The hexagonal grid was generated using Shapely and G eopandas with hierarchical spatial indexing system\, producing hexagonal c ells with an almost equivalent spatial resolution to the rectangular grid. To keep the overall grid coverage comparable to the rectangular represent ation\, 4\,007 hexagonal cells were generated to cover the study area. The rectangular grid had a side length of 1.0 km\, whereas the hexagonal grid had a slightly larger side length of 1.074 km. Each hexagonal cell has a circumradius of 620m and a cell area 0.999km square approximately equivale nt to 1km square rectangular grid ensuring comparable spatial resolution b etween two tessellations. From these two tessellation we set four spatial weight configurations which are\; Rook\, standard Queen\, Distance-Weighte d Queen and Hexagonal KNN-6 and then calculated the spatial autocorrelatio n.\n\nWe found Global spatial autocorrelation analysis confirmed significa nt and positive clustering of A. bungii occurrences across all configurati ons Moran's I = 0.4525--0.5380\, Geary's C = 0.5527--0.5970\, Getis-Ord G all p-value = 0.001\, demonstrating that the spatial agglomeration charact eristic is robust to the choice of tessellation geometry and neighbourhood definition. Local spatial autocorrelation analyses consistently identifie d two primary hotspot zones at the northern (Kazo--Gyoda) and the southeas tern (Soka) parts of Saitama Prefecture across all configurations\, provid ing spatially explicit evidence of persistent infestation core that may se rve as priority zones for targeted surveillance and countermeasure deploym ent.　Across all configurations hotspot areas were consistent\, however c oldspot delineation was found to be unstable with certain configurations i nconsistent coldspot that undermine the accurate identification of managem ent priority zones.\n\nHexagonal tessellation produced higher counts of si milar cells associated with hotspot clusters compared to rectangular confi gurations due to six- neighbourhood structure equidistant by design\, ensu ring the spatial relationships are evaluated uniformly in all directions t hereby reducing directional bias. In contrast\, rectangular configurations evaluate neighbours at unequal distances\, introducing directional bias t hat result in fragmented cluster boundaries and lower hotspot cell counts. The inconsistency of coldspot indicating the spatial clustering outcomes are sensitive to tessellation choice. Practitioners should therefore consi der the tessellation configuration carefully when interpreting spatial clu ster results for management planning\, as different configurations may lea d to different prioritisation of monitoring and eradication efforts\, spec ifically at cold spot areas. \n\nThe limitation of different geometry stru cture should be acknowledged. Although\, the comparable spatial resolution were used\, the exact areal equivalence between rectangular and hexagona l tessellation could not be perfectly achieved due to their difference geo metric structure. DTSTAMP:20260717T234907Z LOCATION:Cosmos1 SUMMARY:Rectangular vs Hexagonal Grid Tessellation for Spatial Analysis of Invasive Species: A Case Study of Aromia bungii in Saitama\, Japan. - Naru masa Tsutsumida\, Irhamillah URL:https://talks.osgeo.org/foss4g-2026/talk/WAXYEY/ END:VEVENT END:VCALENDAR