In 2014, a mission for new global DEM construction was completed as part of the TanDEM-X satellite missions with a relative vertical accuracy of approximately 2 m using height of ambiguity, which was defined as the altitude difference corresponding to flatted interferometric 2\(\pi\) phase change, ranges from 30 to 45 m [23]. The height of ambiguity is inversely proportional to the perpendicular baseline in the radar geometry. Nearly simultaneous observations using TanDEM-X and close flight formation in a helical orbit facilitates a very high coherence (e.g., a reduction in temporal decorrelation and atmospheric artifacts), even on a rapidly varying surface such as an ice stream [24]. However, a moderate height of ambiguity (>30 m) from the short perpendicular baseline in the TanDEM-X operational mode might not be suitable to represent detailed topographic features in a low gradient area, such as a tidal flat or a glacier. To utilize the small height of ambiguity in a low-slope area, the ERS-Envisat cross-interferometry technique with a large perpendicular baseline of approximately 2 km and a short temporal baseline of 30 min was introduced [25]. Although it has been successfully adopted for various applications [26; 27; 28], the 30 min of temporal baseline can have a significant decorrelation effect on a rapidly moving surface, such as a tidal flat or a glacier. In addition, very limited data was acquired because the cross InSAR acquisition mode was experimentally conducted and both satellites were gone. A few studies to calculate mass or elevation changes in glaciers using multiple topographic observations have been reported [19; 20]. However, the calculated DEMs might not show detailed topographic characteristics because of the relatively large height of ambiguity. After the global TanDEM-X DEM mission, the TanDEM-X Science Phase mode was conducted temporarily from October 2014 to December 2015, over 15 months, to experiment with special orbital configurations for scientific purposes [29]. A large perpendicular baseline and a very short or no temporal baseline from the TanDEM-X observations during the Science Phase is preferable to construct more accurate DEMs over low-relief areas, such as intertidal or glacial surfaces [30]. In this study, we examined the feasibility of the TanDEM-X pursuit monostatic observation acquired during the TanDEM-X Science Phase to construct high-resolution and highly sensitive topographic elevation models, which could not be achieved using other conventional InSAR observations. The objective of this study was to evaluate the measurement of more detailed topographic height variation along moving surfaces of low slope like a glacier, using a single TanDEM-X Science Phase observation. The study area selected was the Petermann Glacier, for its low-gradient surface to develop more precise topographic information. First, the absolute topographic elevation model with an improved height of sensitivity by large perpendicular baseline formation was estimated using an InSAR technique. Then, an accuracy assessment was performed using existing DEMs, such as the Greenland Ice Mapping Project (GIMP) DEM and global TanDEM-X DEM, CryoSat-2 radar altimeter observations (SAR/Interferometric mode (SARIn)), and IceBridge Airborne Topographic Mapper (ATM) laser altimeter measurements.