Ephemeris and almanac are used as basic concepts on which the cold start function is based. The essence of these terms will be discussed below. Users of modern technology have little interest in the internal processes of its work. The navigator is no exception, which is widely used today for various purposes to obtain accurate coordinates.
The mechanism of this device is very simple. With a couple of finger movements, you can sketch out a future route in a minute. After turning on, the device determines the exact coordinate location of its owner in seconds.
To understand the characteristics of the technical side that are inherent in this type of technology, and even more so to understand how to make a cold start on the navigator, it is not enough just to get acquainted with the basic information necessary for use. It is necessary to dig deeper both into the terminology itself and into the structure of the apparatus and the operation of its functional side.
Basic terminology
To understand how GPS cold start and hot start work, you need to understand some basic terminology. Every field of technology and science is full of terms. Despite the relative mystery of the first heard word, when parsing the meaning, it acquires a completely understandable and conscious meaning.
The theory of space navigation is considered:
- movement of satellites;
- signal reception, processing, transmission;
- signal coding.
As mentioned earlier, hot start and cold start are terminologically dependent. Let us consider in more detail the concepts of almanac and ephemeris.
How the almanac is used in navigation
Many are familiar with the term "almanac". And for the first time this word could be heard at school. In fact, an almanac is considered to be a kind of reference book containing the main information data of astronomical significance. Such data include the positions of celestial bodies in outer space, the specifics of linking their movement to calendar days. The oldest almanac on Earth is the book "Tong Xing" from China.
By the time of the appearance of navigators that have hot and cold start, nothing has changed in the purpose of almanacs. Changes have undergone only the data itself, or rather their number. Taking into account the development of modern technologies, as well as the peculiarities of the functioning of the most complex equipment, the data in the almanacs have become more extensive and accurate.
The almanac used in modern space navigation is a set of data that includes information about all the main orbital parameters within which satellites move through the navigation system.
Almanac hassix orbital parameters belonging to the satellites. And each of them is valid for a certain period of time. Each satellite of this system has data on other satellites. As a result, the navigator, establishing a connection with only one of them, upon receiving the almanac, "learns" data on all their other orbits.
When downloading the almanac to the memory of the navigator, the user can use this information for 30 days. Despite this, data refinement occurs much more frequently. This process is carried out during the connection with one of the existing ground stations once every few days.
Ephemeris specifics
Cold start is also guided by data such as ephemeris. They are used to calculate orbital deviations, perturbation factors, and more. In other words, ephemeris not only helps to determine the positions of satellites, but also makes it possible to do this with high accuracy.
Those ephemeris, which carry the most accurate data, are the fastest to become obsolete. The activity of this information lasts only 30 minutes. This data is also updated by ground stations.
The importance of this data in order to make a hot or cold start in the navigator is obvious. Without information about the location of navigation satellites, it is impossible to determine the coordinates of the receiver. This requires four satellites.
Algorithm used in the navigator
Understand the general principles by which a cold start occurs in the navigator,not difficult. But if we talk about the algorithm that operates in the device itself, then it can only be general. In-depth knowledge can only be possessed by the developers of the navigator.
In general, the action of this device is as follows:
- The enabled navigator is trying to contact one of the existing navigation satellites.
- The first satellite with which it was possible to successfully establish a connection starts transmitting the almanac to the device. It usually contains all the basic orbital information about one constellation of satellites within a particular navigation system.
- Since communication with one satellite is not enough to obtain accurate coordinates (the minimum number of them is 4), the remaining ones start transmitting their ephemeris. Their placement is being clarified.
Cold start features
When you turn on the navigator for the first time or after a long break in work, a cold start is triggered. The user has to wait some time until his own coordinates are received. This will be the GPS cold start time.
The length of the waiting period depends on various reasons:
- from the quality level of the receiving unit installed in the navigator;
- on how many satellites are in the field of view;
- from atmospheric features;
- from the indicator of electromagnetic noise, which is at operating frequencies.
In general, a cold start is a state of the navigator in which its memory does not have anyephemeris and almanac. In some cases, this data may be present, but it will be considered out of date.
To obtain new data, you will have to start a cold start of the GPS and perform all the necessary manipulations.
Cold start action algorithm
Navigator needs to go through a full cycle to receive new data.
Cold start in this case includes the following actions:
- search for the first satellite and try to establish a connection with it;
- obtaining an almanac and storing this data;
- getting and saving ephemeris;
- attempting to establish contact with three other satellites;
- receiving ephemeris from three satellites and storing these data;
- use of ephemeris to calculate own coordinates.
Given how many actions are performed to “warm up” the navigator, it becomes clear why the device takes time during a cold start.
In general, if we draw analogies, such a launch of the navigator resembles a cold engine start in terms of time spent.
Features of warm and hot starts
Hot start of the navigator is characterized by the presence of up-to-date data in its memory - active almanac and ephemeris. The timing has already been considered. It is 30 days for almanacs, half an hour for ephemeris.
A hot start is possible if the power has been turned off for a short period of time. This means that in order to obtain the coordinates, the algorithminclusion will be significantly reduced.
All you need is:
- try to communicate with all satellites;
- if necessary, update the ephemeris and save them;
- calculate your own location using ephemeris.
A warm start makes work much easier. In this state, the navigator has an up-to-date almanac, but it needs to receive updated ephemeris.
Features of the Navitel navigator
"Navitel" is a navigation type software. It is designed for various types of devices equipped with an external or built-in GPS receiver. This program provides downloading maps of various countries in a detailed form.
These cards contain:
- house numbering;
- street names;
- names of subway stations and more.
Cold start "Navitel" implies that unknown indicators are time, ephemeris, position, almanac. The shutdown threshold at which data is lost by the navigator is 70 hours or more. This can be facilitated by the transportation of the navigator over long distances in the off state. The process of obtaining data in this case has already been described earlier. Cold start time can last more than 20 minutes.
Many drivers purchase a Webasto cold start kit for their cars. After all, the car engine during downtime in the cold season also needs to be warmed up, as well asnavigator.
If we talk about the warm and hot start of the Navitel navigator, it should be noted that the scheme of action is similar. Only with a warm start, the device is activated after a few minutes. When hot, the coordinates are calculated in less than a minute.
Advantages of Navitel navigator
There are many similar programs. But in comparison with them, Navitel has many advantages.
Device Advantages:
- fast map zooming and scrolling system;
- switching process is automated;
- the ability to choose the orientation of the map based on the direction in which the movement is carried out, or based on the location of the north;
- full-screen perception of information;
- 2D and 3D modes;
- tooltip function.
The functional side of the device supports many features, including determining the current position on the map, displaying it, laying a route (manually or automatically), etc.
