BEGIN:VCALENDAR VERSION:2.0 PRODID:-//pretalx//talks.staging.osgeo.org//foss4g-europe-2025//talk//8MU9G H BEGIN:VTIMEZONE TZID:CET BEGIN:STANDARD DTSTART:20001029T040000 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10 TZNAME:CET TZOFFSETFROM:+0200 TZOFFSETTO:+0100 END:STANDARD BEGIN:DAYLIGHT DTSTART:20000326T030000 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3 TZNAME:CEST TZOFFSETFROM:+0100 TZOFFSETTO:+0200 END:DAYLIGHT END:VTIMEZONE BEGIN:VEVENT UID:pretalx-foss4g-europe-2025-8MU9GH@talks.staging.osgeo.org DTSTART;TZID=CET:20250717T151000 DTEND;TZID=CET:20250717T151500 DESCRIPTION:Monitoring the urbanization process and early detection of ille gal construction should enable meaningful urban planning and the protectio n of natural and cultural features of the community. Remote sensing method s can greatly assist in these activities today. There is a major problem o f illegal construction in the Republic of Croatia. In 2023 alone\, accordi ng to a report by the State Inspectorate of the Republic of Croatia\, a to tal of 4\,774 inspections were carried out on the territory of the Republi c of Croatia\, and 1\,089 inspection procedures were initiated due to viol ations of construction regulations. Based on them\, 791 decisions were mad e on the removal of illegal buildings (State Inspectorate of the Republic of Croatia\, 2024). Illegal construction undermines the quality of life of individuals and communities because it generally involves disregard for u rban planning rules\, damages the environment\, reduces green areas\, incr eases the risk of urban heat islands\, and burdens municipal infrastructur e.\n\nThis research uses the differences in spectral indices calculated us ing satellite images from different time periods. The assumption is that t he use of the obtained differences in spectral indices from different time periods\, in integration with open data in the form of digital orthophoto images and known data on illegal construction\, could enable greater expe diency of services in sanctioning premature and illegal construction or ot her environmental devastation.\n\nThe aim of this analysis is to examine a nd determine the possibilities of applying remote sensing methods in the e arly detection of areas under construction or other types of devastation. The assessment of the quality and usability of the results will primarily focus on the thematic accuracy and reliability of the detection of areas u nder construction through the use of high and medium spatial resolution im ages for the evaluation of the results. This research uses images from the Sentinel-2 and PlanetScope satellite systems. The idea was to examine the possibility of using a system that provides free imagery and has problema tic spatial resolution for monitoring illegal construction\, and a better spatial resolution system that is commercial. The impact of the spatial re solution of the high-resolution satellite imagery of the PlanetScope satel lite system (spatial resolution 3 m) and the medium-resolution satellite i magery of the Sentinel-2 satellite system (spatial resolutions 10 m and 20 m) on the accuracy of the obtained results was also analyzed.\n\nTen spec tral indices were calculated using images from the Sentinel-2 and PlanetSc ope satellite systems for two reference dates (2017 and 2021). The indices were selected by researching relevant literature. One of the results of t his research is to highlight the indices that gave the best results for th e purpose of detecting illegal construction. The city of Solin (near Split )\, Croatia\, with its wider surroundings\, was selected for the research area.\n\nOn cadastral plots with a known change in development (it is know n that an illegal building was built there)\, the results obtained for the calculated differences in spectral indices were evaluated through visual analysis. Visual analysis means that the spectral index results are displa yed over a digital orthophoto image with a spatial resolution of 0.5 m. Al though previous research suggests that the BAEI and NDTI spectral indices should be suitable for separating built-up areas\, satisfactory results we re not obtained in this study. The same thing happened using the differenc e of the spectral indices NDBI and DBSI. Both spectral indices did not sho w good results in cases where smaller buildings were built on mixed-use la nd\, so there is no significant difference in the spectral response for th e two observed dates. The BRBA and NBAI spectral indices difference images stood out from the others because in some cases\, changes in the structur e of gravel and similar materials were successfully detected\, and accordi ng to previous research\, such detection represents the biggest challenge. It is worth highlighting the results obtained using the NBI spectral inde x\, because in the figure\, the differences in the spectral index of chang es in development stand out best in relation to the environment. The best results were achieved with the difference of NDVI spectral indices calcula ted using the spectral channels of the Sentinel-2 and PlanetScope satellit e systems. According to the achieved results\, it is evident that for this type of research\, the spatial resolution of the used spectral channels ( 3 m PlanetScope and 10 m Sentinel-2) did not have a major impact on the ac curacy of detection.\n\nAfter the described analysis\, the model was verif ied in another area\, as a blind test. The verification model was conducte d with five spectral indices (NDVI\, NDVI (calculated with PlanetScope cha nnels)\, NBI\, BRBA and NBAI) which gave the best results. The blind test area was conducted in the Podstrana municipality (also near Split)\, Croat ia. One urban and one rural location within the settlement were selected. From the obtained results\, it can be concluded that the detection success of the verification model corresponds to the accuracy of the development model for detecting changes in built-up area\, where the analysis with spe ctral indices NDVI\, NDVI (calculated with PlanetScope channels) and NBI s howed the best results.\n\nThe purpose of this method of detecting illegal construction has proven to be very practical in rural areas where the res ulting images of differences were compared with official data on existing illegally constructed structures. From the obtained results\, it can be co ncluded that for areas with a Mediterranean climate\, the use of the diffe rence method of spectral indices NBI\, NDVI and NDVI (calculated by Planet Scope channels) gives very good results that can be of great use for the i nitial control of illegal construction. DTSTAMP:20260527T195037Z LOCATION:PA01 (Quarticle) SUMMARY:TEMPORAL ANALYSIS OF MULTISPECTRAL SATELLITE DATA FOR THE PURPOSE O F URBANIZATION MONITORING - Andrija Krtalić URL:https://talks.staging.osgeo.org/foss4g-europe-2025/talk/8MU9GH/ END:VEVENT END:VCALENDAR