Home | Trees | Indices | Help |
---|
|
object --+ | GPSString
A GPSString is any string that contains a complete NMEA string someplace within it. The string must start with the leading $ and end with the *hh where hh is the checksum.
|
|||
FailedChecksum A class creating the exception FailedChecksum, which is derived from the standard exception.Warning. |
|
|||
|
|||
|
|||
|
|||
|
|||
|
|||
|
|||
|
|||
|
|||
|
|||
Inherited from |
|
|||
GPS_IDs =
|
|
|||
msg The message containing the gps string. |
|||
debug A flag for writing debugging information |
|
|||
Inherited from |
|
Initializes the class with any string containing a single NMEA data string.
|
This method identifies the string within gps_string, returning an ID index which is required to parse the string. Currently the following message types are supported: GGA, ZDA, RMC, GST, GSV, VTG, HDT, PASHR |
This method pareses a GPSString, defining a set of attributes for the class with the parsing results. How each string is parsed is dependent on the type of string. In any case, the fields returned are defined in "self.fieldnames". Before parsing the string's checksum if verified. The GPSString.FailedChecksum exception is raised if the checksum fails. [NOTE: The checksum verification may cause problems for some gps systems which do not calculate the checksum on the proper portion of the string. The NMEA standard specifies calculation on the portions of the string __between__ the leading "$" and "*", but not to include either. ] A few general rules are in order. Time stamps are converted to datetime objects. Several GPS strings contain only time fields with no year, month, or day. If gps_string.date is defined with a datetime.date object (i.e. mygpsstring.date = datetime.date(2008,12,1) ) prior to calling the parse() method, the final datetime object will combine the pre-set date with the gps parsed time value. If gps_string.date is not defined the returned datetime object returned from the parse() method will reflect the gps time as a datetime.time() object. Latitude and Longitude are converted to decimal degrees with negative values for the Southern and Western hemispheres. They are reported to 8 decimal places which equates to just over 1 mm precision. Some fields are not parsed because they do not typically change. The units fields of meters for geoid separation in the GGA string is a classic example. |
An internal method to convert gps time strings to datetime.time objects (default) or datetime.datetime objects when GPSString.date is pre-defined with a datetime.date object.
|
Converts latitude strings of arbitrary precision to decimal degrees to 10 decimal places of precision (about .000001 meters).
|
Converts longitude strings of arbitrary precision to decimal degrees to 10 decimal places of precision (about .000001 meters at the equator).
|
Strips and ISO 8601 time stamp from the GPSString and returns a datetime object. For many scientific applications GPS strings are logged with the logging computer's date-time stamp. When these time stamps are in ISO 8601 format, this method will extract and parse them, returning a datetime object. |
Converts a datetime stamp in the form of a datetime object to a tab-delimited vector of numeric values.
|
A function to calculate and return a checksum of a NMEA string.
|
|
GPS_IDs
|
Home | Trees | Indices | Help |
---|
Generated by Epydoc 3.0.1 on Mon Dec 8 18:05:06 2008 | http://epydoc.sourceforge.net |