NMEA Data Fields
Data Fields represent the smallest element a sensor's data stream can be broken down into. Each Data Field should correspond to a single data item such as a Latitude, Longitude, Course, Speed, Depth, etc. NMEA Data Fields are parsed out of the full RAW data string by splitting on the comma. For instance, below is the start of defining the indices of the fields from a full GPS RAW message:
Note index 0 is the sentence label itself!
$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47
| Index |
Data Field Value |
|
0
|
$GPGGA
|
| 1 |
123519
|
| 2 |
4807.038
|
| ..... |
..... |
The Basic tab consists of the following fields:
- Description
- Provide an optional description of this item.
- System Name
- System generated name, read only format standard across all SCS systems.
- Useful for post-processing data on shore from multiple different sources/vessels.
- Useful for rotating personnel as each ship will always comply with this format.
- If you wish to have a more user friendly name you can edit the Display Name attribute below
- Display Name
- User supplied name
- Can be anything you wish though must be unique.
- Type
- The Type of DataField Interface being defined.
- This is set upon creation and cannot be changed after the fact.
- Category
- The category/genre of data this field should fall into.
- This must be set appropriately as many calculated interfaces and other sub-systems rely on this setting to filter and generate their inputs/outputs.
- Units
- The unit of data this field's value is in
- Is Eligible Base Field
- A flag letting CFE know if this field should be selectable when generating calculated interfaces and equations.
- This flag will also block usage of this field in QA/QC.
- Calculated Interface References
- Will appear if this field is used by any calculated interfaces, hidden otherwise.
- Will show you all Calculated Interfaces using this field and provides a button to quickly navigate you to them.
- Data Field Position
- The index (0-based, but position 0 is the sentence label so all data fields should START at 1).
The Advanced tab consists of the following fields:
- Comment
- A general comment pertaining to this item
- Keywords
- Optional tags used to assist with text searches and metadata
- Precision
- The number of digits after the decimal point
- Include as Data Source for Category
- A flag letting SCS know if the field should be considered as a reference source for it's category.
- Priority of this field is relative to others in the same category based upon the installed Physical Device Reference Order
- Exclude from SAMOS calculations
- A flag letting SCS know if the field should be averaged and sent to SAMOS.
- Only applies to fields SAMOS are interested in (eg has no effect on data that wouldn't be going to SAMOS regardless, such as 'winch tension')
- Code Translations
- A table of data field values and their translations. It is used to translate coded data field values into a string meaningful to users. The translated string replaces the original code in the RAW file and in all data displays
Latitude / Longitude Categories
If you set the fields category to a Latitude or a Longitude you must also specify the format.
Default format for latitude and longitude data in NMEA is Degrees-Minutes. eg 4124.8963, N which maps to 41d 24.8963' N or 41d 24' 54" N
In the Advanced tab you must also specify the Lat/Lon Direction Field Position (the North/South East/West portion of the data).
Time / DateTime Categories
If you set the fields category to a Time or Date/Time you should specify the format of the timestamp string.
Default format for Time data in NMEA GPS is HHmmss.f. eg 170834 which maps to 17:08:34 Z
Geographic Point Category
The Geographic Point Category is used internally by SCS, you should not use it in your normal course of building out your configuration in CFE.