RFID　is　one　of　the　indispensable　technologies　employed　to　implement　the　Internet　of　Things,　where　it　facilitates　the　identification　and　awareness　of　objects　in　our　daily　lives　by　integrating　backscatter　tags.　The　interference　synthetic　aperture　radar　(InSAR)-based　localization　scheme　provides　high　precision　in　3-D　conditions,　although　it　still　has　some　practical　problems　such　as　its　strict　sampling　operation　and　it　is　also　highly　time　consuming.　In　this　article,　we　developed　E3DinSAR　as　an　optimized　InSAR-based　3-D　localization　approach　for　pinpointing　tags　rapidly　and　easily　with　high　accuracy.　E3DinSAR　does　not　use　any　other　infrastructure　or　reference　tags,　and　only　one　movable　reader　with　one　antenna　is　sufficient　to　implement　the　localization　method,　where　it　measures　the　phase　value　of　the　tag　at　different　positions　throughout　its　movement　in　order　to　create　multiple　holographic　images.　In　contrast　to　the　previously　proposed　InSAR-based　technique,　we　extend　the　sampling　trajectory　of　the　reader　to　an　arbitrary　curve　by　restricting　it　to　several　approximate　linear　apertures,　which　allows　more　flexible　operations　and　increase　the　accuracy.　We　also　employ　a　rapid　computing　method　to　calculate　the　results　for　the　holographic　images　by　estimating　the　direction　of　arrival　for　the　tag.　Experiments　were　performed　where　E3DinSAR　was　implemented　with　commercial　off-the-shelf　(COTS)　RFID　products　and　our　systematic　evaluation　showed　that　E3DinSAR　achieved　a　mean　locating　accuracy　of　18.4　cm　in　a　3-D　space.