Passenger　transportation　is　one　of　the　primary　sources　of　urban　carbon　emissions.　Travel　data　acquisition　and　appropriate　emission　inventory　availability　make　estimating　high-resolution　urban　passenger　transportation　carbon　emissions　challenging.　This　paper　aims　to　establish　a　method　to　estimate　and　analyze　urban　passenger　transportation　carbon　emissions　based　on　sparse　trip　trajectory　data.　First,　a　trip　chain　identification　and　reconstruction　method　is　proposed　to　extract　travelers＇　trip　information　from　sparse　trip　trajectory　data.　Meanwhile,　a　city-scale　trip　sampling　expansion　method　based　on　population　and　checkpoint　data　is　proposed　to　estimate　population　movements.　Second,　the　identified　trip　information　(e.g.,　trip　origin　and　destination,　and　travel　modes)　is　used　to　calculate　multimodal　passenger　transportation　CO2　emissions　based　on　a　bottom-up　CO2　emissions　calculation　approach.　Third,　we　develop　a　multi-scale　high-resolution　transportation　carbon　emission　calculation　and　monitoring　platform　and　take　the　city　of　Hangzhou,　one　of　China＇s　leading　cities,　as　our　case　study,　with　around　10　million　daily　trips　data　and　a　quarter　million　road　links.　Five　modes　of　passenger　transportation　are　identified,　i.e.,　walking,　cycling,　buses,　metro,　and　cars.　Hourly　carbon　emissions　are　calculated　and　attributed　to　corresponding　road　links,　which　build　up　passenger　transportation　carbon　emissions　from　road　links　to　region　and　city　levels.　Results　show　that　a　typical　working　day＇s　total　passenger　transportation　CO2　emission　is　about　36,435　tonnes,　equivalent　to　CO2　emissions　from　4　million　gallons　of　gasoline　consumed.　According　to　our　analysis　of　the　carbon　emissions　produced　by　approximately　40,000　km　of　roadways,　urban　expressways　have　the　most　hourly　carbon　emissions　at　194　kg/(h.km).　Moreover,　potential　applications　of　the　developed　methods　and　platform　linking　to　smart　mobility　management　(e.g.,　Mobility　as　a　Service,　MaaS)　and　how　to　work　in　tandem　to　support　green　transportation　policies　(e.g.,　green　travel　rewards　and　carbon　credits　in　transportation)　have　been　discussed.