Knockoutjs谷歌地图绑定与Ajax调用

I have scratched my head on this code with extensive reading and tinkering but can't seem to get myself to apply knockout js on google maps. Let me know if am on the right track. I am rendering a map with some default markers (which is working as intended) then want to update them with points derived from making an ajax call triggered by on change event on the select form. It is possible I am missing on something very basic as this is the first time am using google maps with KO and not quite sure where to separate the V and the VMI have scratched my head on this code with exte