What is it you exactly want to do with the gps data? About 18 months back I needed to work with gps data and obvioulsy chose LC for the project and logically the XML functions for the job. Like you, I had a great deal of trouble with XML but soon realised that the gpx files were so well 'worded' that LCs own word chunk expression was about 98% up to the task. I think I did a bit of pre-pruning and then simply used a repeat for each loop to go through every line of the file and place the data into an array. Your data looks smaller than what I was dealing with, mine had a time stamp every second and 8 data points associated with that time. I simply created the array using the time as the primary key and data headings as the secondary keys.
In my case I needed to transform gpx files into human readable data, so it was a simple case of read the files in then close, process in LC, then output the specific data. I know it took me one day to throw together the script which was able to process 100+ files totalling just over 1 million datapoints in a couple of seconds. If your task is to fiddle with the gpx file itself and still have a valid file format when done, then that may be more complex than what I was doing, but again, the format is very straight forward and I think would still be doable using LC's basic chunk expressions. HTH On Thu, Sep 19, 2013 at 12:19 AM, Graham Samuel <livf...@mac.com> wrote: > I have been asked to do some work on some GPX files: these files originate > from GPS devices, and are in XML format. I've never had to deal with XML > before, so I have been trying to learn how to do so from the LC user manual > - from about page 189. There is a sample XML file and a discussion of the > various 'revXML' functions which are on offer. There are a few typos, but > it doesn't **look** hard. > (I don't have any other source of information since my crazy ISP has cut > off my internet connection, and I am confined at present to emails sent & > received via a friend.) > > So far, so good: however, although I can create an XML tree and retrieve > the Root Node as per the documentation, I can't make any of the other > functions work on my data. I hope someone can explain the fundamentals of > what I'm doing wrong. > > My GPX file begins like this: > > <?xml version="1.0" encoding="UTF-8"?> > <gpx xmlns="http://www.topografix.com/GPX/1/1"; creator="Geolives" > version="1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; > xsi:schemaLocation="http://www.topografix.com/GPX/1/1 > http://www.topografix.com/GPX/1/1/gpx.xsd";> > <metadata /> > <trk> > <trkseg> > <trkpt lat="42.78981" lon="1.336446"> > <ele>750.5912</ele> > </trkpt> > <trkpt lat="42.78981" lon="1.336446"> > <ele>750.5912</ele> > </trkpt> > [etc etc etc] > > The file seems to be well-formed, apart from the fact that the first child > node is found by revXML to be "gpx/metadata", and I can't see the closure > for the metadata tag at the other end of the document. In fact the document > ends </gpx>f I try to stick in </metadata> before this last line, the LC > function refuses to form the table, so the original file must be right. I > don't understand this. > > Anyway, revXMLRootNode returns "gpx" (without the quotes) > > and revXMLFirstChild returns "/gpx/metadata" > > but after that nothing works. However closely I follow the example in the > manual, I can't get the revXMLContents or revXMLNodeContents functions to > return anything. For example (among many attempts), > revXMLNodeContents(1,"/gpx/metadata/trk/trkseg") returns > > "xmlerr, can't find element" > > I feel like I've tried everything, but it seems there's something basic I > haven't grasped. XML seems like a simple idea, but in practice it's > dreadfully easy to slip up. > > TIA for any advice, as long as it doesn't mean significant downloading. > > Graham > > > Sent from my iPad > _______________________________________________ > use-livecode mailing list > use-livecode@lists.runrev.com > Please visit this url to subscribe, unsubscribe and manage your > subscription preferences: > http://lists.runrev.com/mailman/listinfo/use-livecode > _______________________________________________ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
