Hotspot Center Locator for MySejahtera app
Theoretically, this is possible to locate the center of hotspot if only 1 covid19 case around the area, by walking around the area and collect the there have been 1 reported case(s) of COVID-19 within a 1km radius from your searched location in the last 14 days. data. When no case means outside of the boundary of hotspot circle, while the 1 case means inside the hotspot. And eventually figure out the center of the hotspot.
The basic flow is, figure out direction west/east/north/south/southeast/northeast/northwest/southwest based on 1km outer of current position, which case 1(inner) is the direction it need to follow until hit case 0(outer). Walk straight on that direction from 500 M step until hit the 0 case from case 1. Then fallback one step and retry with 500 M/2 = 250 M step, and until retry 6 CM step. Then walk the opposite side(I call 2 sides either of major(area) or minor(area) side) and repeat the walk steps. Then it get the chord line which can get a perpendicular line in the middle. Then repeat the 2 sides walk on that perpendicular line direction. Eventually it get diameter of hotspot circle, which can simply divide diameter by 2 to locate the center. To avoid false positive causes by outer has another hotspot nearby, it check <2 case in every step, and also distance of walk to ensures only walk 2km on that diameter. At the beginning, It also do basic(not covers all) checking 1km outer of current position to abort early if >1 cases.
