Changeset 3102 in ntrip

Timestamp:

Mar 10, 2011, 8:31:34 PM (13 years ago)

Author:

weber

Message:

Wording improved

File:

• trunk/BNC/bnchelp.html (modified) (1 diff)

trunk/BNC/bnchelp.html

@@ -1383 +1383 @@
 <p>
 BNC allows to process several orbit and clock corrections streams in real-time to produce, encode, upload and save a combination of correctors from various providers following a Kalman Filter approach. It is only the satellite clock corrections which are combined here while orbit correctors in the combination product as well as the product update rates are just taken over from one of the incoming corrections streams. 
-
-</p>
-<p>
-The 'Combination' functionality has been integrated in BNC because
-<ul>
-<li>the software with its Graphic User Interface and wide range of supported Operation Systems represents a perfect platform to simultaneously process several incoming broadcast corrections streams.</li>
-<li>outliers and outages of individual Analysis Center (AC) product streams can be reduced through merging several incoming streams into a combined product.</li>
-<li>a Combination Center (CC) can operate BNC to globally disseminate a combination product via NTRIP broadcast.</li>
-<li>an individual AC could prefer to disseminate a stream combined from its primary and its backup resources to reduce outages.</li>
-<li>a BNC PPP user is enabled to follow his own preference in combining streams from individual ACs for Precise Point Positioning.</li>
-<li>it allows an instantaneous quality control of the combination process not only in the time domain but also in the space domain. This can be done through direct application of the combination stream in a PPP solution even without prior stream upload to an NTRIP Broadcaster.</li>
-<li>it enables the output of SP3 files containing precise orbit and clock information for further processing using other tools than BNC.</li>
-</ul>
-</p>
-<p>
-Note that the combination process requires real-time access to Broadcast Ephemeris. So, in addition to the orbit and clock corrections streams BNC must pull a stream carrying Broadcast Ephemeris in the form of RTCM Version 3 message types 1019, 1020, and (proposed) 1045. Stream RTCM3EPH on caster <u>products.igs-ip.net</u> is an example for such a stream.
+</p>
+<p>
+In view of IGS real-time products, the 'Combination' functionality has been integrated in BNC because
+<ul>
+<li>the software with its Graphic User Interface and wide range of supported Operation Systems represents a perfect platform to process many broadcast corrections streams in parallel;</li>
+<li>outages of single Analysis Center (AC) product streams can be neutralized through merging several incoming streams into a combined product;</li>
+<li>generating a combination product allows detecting and rejecting outliers;</li> 
+<li>a Combination Center (CC) can operate BNC to globally disseminate a combination product via NTRIP broadcast;</li>
+<li>an individual AC could prefer to disseminate a stream combined from primary and backup IT resources to reduce outages;</li>
+<li>it enables a BNC PPP user to follow his own preference in combining streams from individual ACs for Precise Point Positioning;</li>
+<li>it allows an instantaneous quality control of the combination process not only in the time domain but also in the space domain; this can be done through direct application of the combination stream in a PPP solution even without prior stream upload to an NTRIP Broadcaster;</li>
+<li>it provides the means to output SP3 files containing precise orbit and clock information for further processing using other tools than BNC.</li>
+</ul>
+</p>
+<p>
+Note that the combination process requires real-time access to Broadcast Ephemeris. So, in addition to the orbit and clock corrections streams BNC must pull a stream carrying Broadcast Ephemeris in the form of RTCM Version 3 messages. Stream RTCM3EPH on caster <u>products.igs-ip.net</u> is an example for that.
+</p>
+<p>
+With respect to IGS, it is important to understand that the biggest effect in the combination of GNSS orbit and clock corrections streams is the selection of ACs to include. It is likely that a combination product could be improved in accuracy by using only the best two or three ACs. However, with only a few  ACs to depend on, the reliability of the combination product could suffer and the risk of total failures increase. So there is an important tradeoff here that must be considered when selecting streams for a combination. The major strength of a combination product is its reliability and stable median performance which can be much better than that of any single AC product.
 </p>