Abstract: In some implementations, the techniques may include at a first time: performing, using a first sensor, a first ranging measurement with a second device to obtain a first distance; and performing, using a second sensor, a first altitude measurement to obtain a first altitude. In addition, the techniques may include at a second time: performing, using the first sensor, a second ranging measurement with the second device to obtain a second distance; and performing, using the second sensor, a second altitude measurement to obtain a second altitude. The techniques may include determining a ranging difference between the first distance and the second distance. Moreover, the techniques may include determining an altitude difference between the first altitude and the second altitude. Also, the techniques may include determining whether the second device is on a different floor of a building than the first device.

Abstract: In some implementations, techniques may include at a plurality of times while a user of the first portable device is moving with the first portable device: performing ranging at a respective position with a second device to determine a respective distance, thereby determining a plurality of respective distances, where the second device is stationary; obtaining raw measurements from a motion sensor of the first portable device. In addition, the device may include using the raw measurements at the plurality of times to determine relative positions at the plurality of times, the relative position from an initial position. The techniques may include estimating a second position of the second device that optimizes a loss function that includes differences of the respective distances at the relative positions and the actual distance between the relative positions and the second position.