One of the first spatial concepts we learn when we are children is the relative position of an object, like above the table, under the bed, in front of me, behind my mom, next to the chair. During our life we refine these concepts by introducing the notion of cardinal points, the idea of a reference system and coordinates (first of all to play battleship), until we understand their practical usefulness in giving road information. Imagine you are in a city you never have been and you do not have any map, neither digital or paper. You are looking for a museum and so you ask information to a person for locating it and going there. How often do you believe you will receive good, sharp and reliable indications? Despite the apparent simple question, even if the person you stopped knows perfectly the city, it is not assured he will be able to allow you to go easily to the museum because his information will be confused and puzzling.
其中之一，当我们的孩子，我们学会第一届空间概念是物体的相对位置，如表上面 ，床底下 ， 在我面前 ，我妈妈身后 ， 旁边的椅子上。 在我们的生活中，我们通过引入基本点的概念，参考系统和坐标的概念(首先是玩战舰 )来完善这些概念，直到我们了解它们在提供道路信息方面的实际用处。 想象一下，您在一个从未去过的城市中，没有电子或纸质地图。 您正在寻找博物馆，因此您向某人询问信息以找到它并前往那里。 您认为您多久会收到一次良好，清晰和可靠的指征？ 尽管存在明显的简单问题，即使您停下的人完全了解这座城市，也不能保证他会允许您轻松前往博物馆，因为他的信息会令人困惑和困惑。
In our digital world geo-location of any information is so important in each field, from business to politics, from science to engineering and so on, that we give it for granted. But providing properly geo-spatial data is not as immediate as can be thought. Traffic Infomation Systems (TIS) are paramount examples of how crucial is the accuracy in location referencing. In such systems the base goal is to be able to transfer traffic information from a producer actor to a consumer actor in a way that is reliable and compact. The location of the traffic information can be a point, a polyline or a two-dimensional shape on the surface of the Earth, while the Location Reference (LR) is a representation of such location. I’ll describe the most common location reference types, but before doing that a brief historical excursus is given.
在我们的数字世界中，从商业到政治，从科学到工程等等的每个领域，任何信息的地理位置都非常重要，我们认为这是理所当然的。 但是，提供适当的地理空间数据并不像想像的那样Swift。 交通信息系统(TIS)是位置参考准确性至关重要的最重要示例。 在这样的系统中，基本目标是能够以可靠和紧凑的方式将交通信息从生产者角色转移到消费者角色。 交通信息的位置可以是地球表面上的点，折线或二维形状，而位置参考(LR)则代表该位置。 我将描述最常见的位置参考类型，但在此之前会给出简短的历史记录。
RDS-TMC，TPEG和TISA (RDS-TMC, TPEG, and TISA)
At the end of the 80s, thanks to a founded European project called DRIVE (Dedicated Road Infrastructure for Vehicle Safety in Europe), there was the first detailed technical proposal at European level for a RDS-TMC protocol for broadcasting in real-time traffic information and weather data.
Radio Data System (RDS) is a communications protocol standard for transmitting digital information via conventional FM radio broadcast. While Traffic Message Channel (TMC) is the protocol defining the content of the traffic data to be transmitted via RDS in a compact digital form. After several proposals the final TMC protocol adopted was the ALERT-C (name inherited from a previous project called RDS-ALERT, and being the C the third specification after A and B).
A no-profit organization, TMC-Forum, was born to discuss traffic information related matters and maintained the TMC-Standard until 2007, when it merged with another organization (TPEG-Forum) giving life to the Traveller Information Services Association (TISA). The Transport Protocol Experts Group (TPEG) is a set of data protocols richer in term of content with respect to the TMC and that can be carried over different transmission media and not only over RDS. TPEG was standardized in a first form as TPEG1 (today deprecated and considered only in legacy systems), but the current ISO standard, supported by TISA too, is the TPEG2 specification.
TMC论坛是一个非营利组织，其诞生是为了讨论交通信息相关事宜，并一直维持TMC标准直到2007年，之后它与另一个组织(TPEG-Forum)合并，为旅行者信息服务协会( TISA ) 增添了活力 。 传输协议专家组( TPEG )是一组相对于TMC而言内容更丰富的数据协议，可以在不同的传输介质上承载，而不仅可以通过RDS承载。 TPEG以第一种形式标准化为TPEG1(今天已弃用，仅在旧系统中考虑)，但是TISA所支持的当前ISO标准也是TPEG2规范。
通过共享同一张地图进行位置参考 (Location Referencing by sharing same map)
The simplest way to transfer geo-spatial data between two actors is when they both have the same identical map in their hands. Despite allowing 100% accuracy, there is a huge downside: updating a map and sharing it among all actors is really cumbersome because it requires high coordination, and it implies a vendor map lock-in. For such reason this solution is almost never used.
在两个参与者之间传递地理空间数据的最简单方法是，当两个参与者手中都拥有相同的相同地图时。 尽管允许100％的准确性，但还有一个很大的缺点：更新地图并在所有参与者之间共享地图确实很麻烦，因为它需要高度的协调，并且这意味着供应商地图锁定。 因此，这种解决方案几乎从未使用过。
通过预编码位置引用位置 (Location Referencing by pre-coded locations)
The first alternative, also from a historical point of view, to the sharing of the same map is the usage of pre-coded locations. It means that the two actors agree on a set of locations codified in some way and fixed until a common agreement of updating them. Each actors has its own map and he has to build for each pre-coded location the corresponding set of links of his map. In such a way when the actor A has to communicate an information located on his links to the actor B, thanks to the mapping to the common shared pre-coded locations, the information can be easily transferred to the links of the other map.
从历史的角度来看，共享同一张地图的第一种选择是使用预编码位置。 这意味着两个参与者在以某种方式编纂并固定的位置上达成一致，直到达成一致同意更新它们为止。 每个演员都有自己的地图，并且他必须为每个预编码位置构建其地图的相应链接集。 通过这种方式，当演员A必须将位于他的链接上的信息传达给演员B时，由于映射到公共共享的预编码位置，因此可以轻松地将信息传递到其他地图的链接。
This location referencing schema is fairly simple even if it requires to build a mapper function between the pre-coded locations and your map, but it is not fully satisfying for the following reasons:
- the pre-coded locations usually do not fully cover the geographical area, so some information can not be transferred 预先编码的位置通常无法完全覆盖该地理区域，因此某些信息无法传输
- the pre-coded location descriptions can not have a high level definition and it implies that the mapper function has some degree of freedom in mapping the links of the map to them, causing lower accuracy of transferred information 预编码的位置描述不能具有较高级别的定义，这意味着映射器函数在将地图的链接映射到它们时具有一定程度的自由度，从而导致传输信息的准确性降低
- some pre-coded locations can not have a mapping to the links in one or both maps due to the map details, and it prevents the possibility to transfer any information 由于地图的详细信息，某些预先编码的位置无法映射到一个或两个地图中的链接，并且它阻止了传输任何信息的可能性
- when there is a map version update or a map vendor switch, there is the need to rebuild/update the mapping between the pre-coded locations and the new map. This is a costly operation that requires some time and in the meantime there will be an outdated provisioning of geo-located information 当有地图版本更新或地图供应商切换时，需要重建/更新预编码位置和新地图之间的映射。 这是一项昂贵的操作，需要一些时间，与此同时，将过时地提供地理位置信息
- when there is a pre-coded location reference update there is a need, as in the case of sharing the same map, of coordination among the several actors for rebuilding/updating the mapping to their own links at the same time, and it can be challenging 当进行预编码的位置参考更新时，例如在共享同一张地图的情况下，需要在多个参与者之间进行协调，以同时将地图重建/更新为他们自己的链接，并且可以具有挑战性的
The master example of pre-coded locations is the ALERT-C location tables used to broadcast traffic information via RDS-TMC.
通过动态位置引用位置 (Location Referencing by dynamic locations)
Another way for location referencing, designed to overcome the struggles of the previously described methods, is the Dynamic Location Refecencing (DLR). It is conceived to be a map agnostic methodology, in the sense that
- the maps of the two actors are totally indipendent (both in term of vendor and version) as for the pre-coded location referencing schema 就预编码的位置引用架构而言，两个参与者的地图是完全独立的(在供应商和版本方面)
- the maps has not to be shared among the actors and there is not any middle layer acting as bridge between the two maps as for the pre-coded location referencing schema 这些地图不必在参与者之间共享，并且就预编码的位置引用架构而言，没有任何中间层充当这两个地图之间的桥梁
There are several DLR methods:
- OpenLR OpenLR的
- TPEG-Loc 聚乙二醇
- AGORA-C 阿古拉
- ULR 超低速
- GIMME 金美
The key common idea of all of them is their capability to encode a location on a given map in a way its information content can be decoded on the other map with a high confidence of success rate. This last one must be intended not only as the correct identified location, but also as the capability to correctly understand that it is not possible to identify a location on a map to the other one. The encoding and decoding procedures rely on algorithms which are specific for each method, and that I will describe in details in future posts.
所有这些工具的主要共同思想是它们能够以给定地图上某个位置的信息内容可以在另一地图上以高成功率置信度进行解码的方式进行编码。 最后一个位置不仅应作为正确识别的位置，而且还应具有能够正确理解不可能在地图上标识到另一个位置的能力。 编码和解码过程取决于每种方法特有的算法，我将在以后的文章中详细介绍。
Traffic data providers like TomTom, INRIX, HERE, use among their location referencing methods also the DLR one, becoming today a de facto standard.