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ch9_handbook:getting_started [2014/08/11 14:11]
bob
ch9_handbook:getting_started [2014/08/11 14:27] (current)
bob
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 So without further adieu, let’s look at an extremely simple TMATS file. So without further adieu, let’s look at an extremely simple TMATS file.
 +
 +a. __RCC IRIG 106 Revision Level__. Identifies the RCC IRIG 106 version of TMATS used to generate the file. The format to describe a Revision Level is 106-xx, with xx as the last two digits of the year. 
 +
 +<​code>​G\106:​09;</​code>​
 +
 +b. Point of Contact (POC) information.
 +
 +(1) __Number of POCs__. Identifies the number of Points of contact (POC) to be given.
 +
 +<​code>​G\POC\N:​1;</​code>​
 +
 +(2) __POC Name__. Identifies the name of the POC.
 +
 +<​code>​G\POC1-1:​ Wile E. Coyote;</​code>​
 +
 +(3) __POC Agency__. Identifies the agency the named POC is associated with.
 +
 +<​code>​G\POC2-1:​ACME Corp;</​code>​
 +
 +(4) __POC Address__. Identifies the agency address.
 +
 +<​code>​G\POC3-1:​123 Roadrunner Way;</​code>​
 +
 +(5) __POC Telephone__. Identifies the named POC contact number.
 +
 +<​code>​G\POC4-1:​(555)555-5555;</​code>​
 +
 +Now, that wasn't so bad, was it? Well, unfortunately,​ this example is not very useful because it does not actually describe anything … but it’s a start.
 +
 +===== Attribute General Syntax and Semantics =====
 +
 +Before we consider a more meaningful example, let's get a general idea of what TMATS 
 +should look like. Each TMATS attribute consists of a unique code name and a data item. The
 +code name appears first, delimited by a colon. The data item follows, delimited by a semicolon.
 +Thus, an attribute appears as A:B; - where “A” is the code name and “B” is the data item.
 +
 +There are two basic types of attribute code names: single entry and multiple entry. Single ​
 +entry attributes are those for which there is only one code name and one data item. Multiple ​
 +entry attributes have multiple indexed code names and data items, each of which corresponds to 
 +an index number. These attribute types allow for lists of like items, such as measurements.
 +
 +a. __Single Entry Example__
 +
 +<​code>​G\OD:​05-11-2009;</​code>​
 +
 +The code name is “G\OD” which is “Origination Date”. ​
 +
 +The data item is “05-11-2009” which indicates May 11, 2009.
 +
 +b. __Multiple Entry Example__
 +<​code>​G\DSI-2:​AIRCRAFT_DATA;</​code>​
 +
 +The code name is “G\DSI-2” which is “Data Source ID’. ​
 +
 +The index “2” specifies that this is the second data source ID.
 +
 +The data item is “Aircraft Data” which is the identification of this data source.
 +
 +Numeric values for data items may be either integer or decimal. Scientific notation is 
 +allowed only for those attributes specifically defined for its use. For alphanumeric data items, ​
 +including keywords, either upper or lower case is allowed; TMATS is not case sensitive. ​
 +Semicolons are not allowed in any data item, including comments. Leading, trailing, and 
 +embedded blanks are assumed to be intentional and must be accounted for if they appear within ​
 +code names or data items. Carriage return (CR) and line feed (LF) may be used to improve ​
 +readability.
 +
 +===== A “Measurement” by any Other Name… =====
 +
 +You might not believe the number of person years that have been spent discussing the 
 +definition of “measurement.” Other words that are related, or possibly mean the same thing 
 +depending on who you ask, are: measurand, sample, parameter, and derived measurement. So 
 +let’s look at the basic process to illustrate.
 +
 +For this example, assume some raw phenomenon exists such as temperature,​ pressure or 
 +velocity. You can also talk about discrete settings such as weight on wheels or other settings or 
 +values that are not necessarily physical phenomena. But let’s start with just real world things ​
 +that we tend to measure. A sensor is placed somewhere to “measure” this phenomenon. Most 
 +sensors are analog devices that “measure” the phenomenon and produce a voltage output
 +(actually, millivolt output). An analog to digital converter (ADC) translates this voltage into a 
 +set of discrete bits. Usually, these bits are the ones that are telemetered. These bits are then 
 +converted using some algorithm into engineering units (EU) such as degrees Fahrenheit or 
 +furlongs per fortnight. The EU data is what engineers like to examine. Now consider that there 
 +isn’t just one sample of each item, but rather a series of samples over time.
 +
 +So there are essentially four things involved here: the raw phenomenon, the voltage ​
 +output of the sensor, the raw digitized data value, and the EU data. Well, there is something of a 
 +fifth thing in the sense that values of different phenomena might be used to “derive” another ​
 +“measurement.” For example, a series of position and time samples might be used to derive ​
 +velocity. Then the sixth thing is the full set of samples of a given phenomenon over time. 
 +Which of these is a measurement,​ sample, parameter, measurand, etc.?
 +
 +A related terminology issue is the concept of “raw” data. Sticking our neck out a little, ​
 +we’ll say that this usually implies the non-EU digitized bits that are telemetered. But the term 
 +can be moved in either direction. That is, someone might refer to the “raw signal” meaning the 
 +voltage output of the sensor or, as used above, the “raw phenomenon.” Or, occasionally,​ the 
 +initial EU data might be considered “raw” since the ultimate analysis is usually presented in 
 +some form derived from these low level measurements. To add to the confusion, there are some 
 +people that talk about “generations” of data, implying that the initial digitized sensor output is a 
 +different generation from the EU or derived calculations.
 +
 +In practice, the words measurement,​ measurand, sample, and parameter are often used 
 +interchangeably. The use of the term “raw” is probably sensitive to context. However, there are 
 +people and systems that make subtle distinctions between these words, so one must be careful. ​
 +This handbook will use the word “measurement” for all of these words, and the word “raw” will 
 +not be used in this document.
 +
 +===== A “Look and Feel” Example =====
 +
 +
 +===== Attributes for the Look and Feel Example =====
 +
 +
 +===== Let’s Talk About Bits =====
 + 
 +
 +==== Bit Masks ====
 +
 +==== Transfer Order ====
 +
 +==== Fragment Order and Concatenation ====
 +
ch9_handbook/getting_started.txt · Last modified: 2014/08/11 14:27 by bob