Linear encoders for nanoscale position sensing based on vertical arrays of single multi-walled carbon nanotubes (MWNTs) are investigated from experimental, theoretical, and design perspectives. Vertically aligned single MWNTs are realized using a combination of e-beam lithography and plasma-enhanced chemical vapor deposition (PECVD) growth. Field emission properties of the array are investigated inside a scanning electron microscope (SEM) equipped with a 3-DOF nanorobotic manipulator with nanometer resolution functioning as a scanning anode. Lateral position of the scanning anode is sensed from the emission distribution. High resolution (best: 12.9 nm; practical: 38.0 nm) for lateral position sensing around an emitter has been realized.