Disclosed in some examples are methods, systems, devices, and machine-readable mediums for providing a PNT system provided by stratospheric balloons. This stratospheric PNT system (SPNTS) replaces the space-segment of a standard PNTS with a stratospheric segment comprising one or more stratospheric balloons that provide PNTS signals usable to determine timing, positioning, and/or navigation for user devices.

A method for generating private eLoran signals includes receiving, by a transmitter that is configured to transmit a transmission at a fixed time, a transmission key; determining, by the transmitter, a pseudo-random transmission time for transmitting the transmission, where the pseudo-random transmission time is determined using the transmission key; and initiating transmission, by the transmitter, of the transmission at the pseudo-random transmission time. A receiving device includes a processor that is configured to obtain a pseudo-random time for receiving a transmission from a transmitter; receive the transmission at the pseudo-random time; and use the transmission to determine at least one of a time, a longitude, or a latitude at the receiving device.

A method for generating private eLoran signals includes receiving, by a transmitter that is configured to transmit a transmission at a fixed time, a transmission key; determining, by the transmitter, a pseudo-random transmission time for transmitting the transmission, where the pseudo-random transmission time is determined using the transmission key; and initiating transmission, by the transmitter, of the transmission at the pseudo-random transmission time. A receiving device includes a processor that is configured to obtain a pseudo-random time for receiving a transmission from a transmitter; receive the transmission at the pseudo-random time; and use the transmission to determine at least one of a time, a longitude, or a latitude at the receiving device.

An eLORAN receiver may include an antenna and eLORAN receiver circuitry coupled to the antenna. The antenna may have a ferromagnetic core including a ferromagnetic medial portion and ferromagnetic arms extending outwardly from the ferromagnetic medial portion, a respective electrically conductive winding surrounding each of the ferromagnetic arms, and an electrically conductive patch element adjacent the ferromagnetic core.

An RF PNT system may include LORAN stations. Each LORAN station may include a LORAN antenna, and a LORAN transmitter coupled to the LORAN antenna and configured to transmit a series of LORAN PNT RF pulses having a time spacing between adjacent LORAN PNT RF pulses. One or more of the LORAN stations may include a message embedding generator coupled to the LORAN transmitter and configured to generate message RF bursts based upon an input message, and with each message RF burst being in the time spacing between respective adjacent LORAN PNT RF pulses.

Provided herein is a method for separating Loran sky and ground waves based on a Levenberg-Marquart algorithm, including: (1) collecting a plurality of Loran sky-ground wave signals followed by normalization to obtain a normalized signal; (2) preprocessing the normalized signal by inverse Fourier transform method to obtain an initialization parameter; (3) establishing a mathematical model for the Loran sky-ground wave signals in time domain; and (4) solving parameters of the mathematical model using the Levenberg-Marquart algorithm to separate the Loran sky and ground waves.

Provided herein is a method for separating Loran sky and ground waves based on a Levenberg-Marquart algorithm, including: (1) collecting a plurality of Loran sky-ground wave signals followed by normalization to obtain a normalized signal; (2) preprocessing the normalized signal by inverse Fourier transform method to obtain an initialization parameter; (3) establishing a mathematical model for the Loran sky-ground wave signals in time domain; and (4) solving parameters of the mathematical model using the Levenberg-Marquart algorithm to separate the Loran sky and ground waves.

A smart landing pad comprises a flexible display that shows images or patterns, and a protective layer over the display. The protective layer allows a UAV to land without damaging the display. Locator and range finder devices, coupled to the display, communicate with the UAV. The display is operative for wireless communications with a computer or mobile device that provides on-demand user functions, allowing for dynamically changing or customizing the images/patterns shown on the display. The images/patterns comprise a background area showing changeable images that match an environment where the landing pad is placed, and a target landing area surrounded by the background area. The target landing area includes a changeable insensitive, contrast portion, and changeable marker pattern portions having changeable colors/shapes. The images/patterns also include changeable QR codes on the target landing area. The display is IoT enabled so that data from the landing pad is remotely cloud accessible.

A geographic tracking system with minimal power and size required at the mobile terminal collects observation data at the mobile terminal, forwards the data to a processor, which calculates the position. The mobile terminal needs only to gather a few milliseconds of observation data, and to relay this observation data to the processor. In one embodiment, the observation data is communicated to the processor using either a satellite communication network or through a mobile telephone network.

A target user equipment (UE), which may be a vehicle or UE carried by a pedestrian, may receive sequentially broadcast ranging signals from a set of ranging source entities (SEs), which may be road side units or other vehicles. The target UE further receives location information separately broadcast by each SEs. The location information, for example, may include the position for the SE, the time of transmission of the ranging signals transmitted by the SE and/or a sequence identifier for the SE. The target UE may determine ranges to the SEs using time of arrival measurements for the ranging signals and the time of transmissions of the ranging signals or the sequence identifier received in the location information. The position of the target UE may be determined using the determined ranges to the SEs and the positions of the SEs received in the location information.