Hi there everyone, Thanks again for all your suggestions and patience! I'll sit down and take a look at it soon and report back on whether or not I can make it work.
Kind regards, Jimi. On Mon, Nov 2, 2020 at 3:03 PM Bernd Vogelgesang <bernd.vogelges...@gmx.de> wrote: > > On 02.11.20 13:57, Fernando M. Roxo da Motta wrote: > > On Sun, 1 Nov 2020 17:26:46 -0500, Garth Fletcher <ga...@jacqcad.com> > > wrote: > > > > Just a side note. > > > > If I understand it correct, this procedure will store in attribute > > table (as a temporary or permanent attribute) the coordinates as they > > are at the time it is stored. If a point is moved through edition that > > value will not be updated automatically. It will be necessary to store > > the new value in the table with the described procedure. > > Yes and no: Since a while, it is possible to update values based on such > a function after doing some configurations. > > First create your x and y fields and apply the $x and $y functions on > them through the field calculator. > > When you now want them to automatically update on changes, go to > > Layer Properties -> Attributes Form -> Pick the field in question -> > Section "Default Values" -> enter the function into the "Default value" > and tick the "Apply default value on update" > > Done ;) > > > > >> My experience is with .gpx files generated by a Garmin eTrex-20. > >> > >> When I use QGIS's Data Source Manager to open a and Add a .gxp file I > >> see several different layers: > >> Tracks > >> Track Points > >> Routes > >> Route Points > >> Waypoints > >> > >> The one you want is "Track Points" because it contains all the > >> individual points which collectively make up the tracks. "Tracks" > >> only contains link(s) to the various tracks that have been recorded - > >> it usually only contains one item unless you have saved multiple > >> tracks. > >> > >> You may also be interested in "Waypoints" if you've recorded specific > >> waypoints on your GPS. > >> > >> So Add the layers of interest (Track Points and maybe Waypoints) > >> > >> Because a .gpx file is "input only", your first step needs to be to > >> to right-click on the layer, select Export > Save Features As... > >> > >> This will let you save the layer in a form that can be edited. Keep > >> this new layer (you can remove the original .gpx layer) > >> > >> The layer's Attribute Table contains fields for all sorts of > >> attributes, but NOT including the location (Lat,Long) data which is > >> stored separately. > >> > >> So to be able to make your own location based calculations you want to > >> copy the point locations into new fields in the Attribute Table. > >> > >> With the layer selected, select the Field Calculator (Abaccus icon in > >> toolbar) > >> check Create a new field > >> enter a name, e.g., "Latid" > >> set Output field type to Decimal number (real) > >> set Output field length to 10, Precision to 6 > >> type "$y" in the Expression window below > >> {$y is the location's Y axis, i.e., its latitude} > >> click OK > >> the first time it may warn you that the layer is not in edit mode and > >> than proceding will turn on edit mode - this is fine > >> > >> Now repeat for a 2nd field, using a different field name and > >> expression "Longid" and $x > >> > >> Now when you open the layer's Attribute Table you will see 2 new > >> fields at the right which contain the point's Latid and Longid > >> values... > >> > >> Save the layer if you want to keep these additions. > >> > >> > >> On 11/1/20 2:17 PM, J. M wrote: > >>> Hi again Garth, > >>> > >>> Well I parked this problem and only just came back to it. I may > >>> have missed something, but when I create the new fields you > >>> suggested in the Track they contain no information. Is this a very > >>> advanced procedure? It seems like something quite basic, but > >>> perhaps I've underestimated it (as I usually do with QGIS!). > >>> > >>> Kind regards, > >>> Jimi. > >>> > >>> On Fri, Sep 11, 2020 at 11:51 AM J. M <jimimc...@gmail.com > >>> <mailto:jimimc...@gmail.com>> wrote: > >>> > >>> Hi Garth, > >>> > >>> Thanks a lot for the very complete answer! I'll give it a go as > >>> soon as I resolve an unrelated Ubuntu problem. I hadn't realised > >>> that GPX data wasn't automatically visible in Properties, and that > >>> fields had to be created. > >>> > >>> Kind regards, > >>> Jimi. > >>> > >>> On Fri, Sep 11, 2020 at 4:26 AM Garth Fletcher > >>> <ga...@jacqcad.com <mailto:ga...@jacqcad.com>> wrote: > >>> > >>> On 10 Sep 2020 at 20:12, J. M <jimimc...@gmail.com > >>> <mailto:jimimc...@gmail.com>> wrote: > >>> > I can successfully import .gpx files into QGIS, and they > >>> > are > >>> visible and > >>> > can be clustered in new groups (waypoints, tracks and > >>> > routes > >>> appear as > >>> > independent layers). The problem I'm having is that I > >>> > can't > >>> seem to find > >>> > any way to access the data about the routes (distance, > >>> > time, > >>> etc) which is > >>> > clearly visible in the app I used to create the tracks > >>> > >>> The GPX file contains a number of fields whose contents you > >>> can see / > >>> access in the layer's Attribute Table > >>> right-click on layer and choose Open Attribute Table > >>> > >>> However, these are only the extra fields in the GPX records > >>> but NOT including the x,y coordinates (Long,Lat) > >>> > >>> To access the later, use the Field Calculator > >>> select the layer > >>> click on Open Field Calculator icon (Abaccus) in the > >>> menu bar which is next to the Open Attribute Table icon in menu, or > >>> in Processing > GDAL > Vector Table > Field Calculator > >>> > >>> create new fields, called Lat and Long, as decimal numbers > >>> and enter the expression $X or $Y (see Geometry > for > >>> details) When you click OK, the new fields will be appended and > >>> filled in with the right values. > >>> > >>> You can then access them in the layer's Attribute Table. > >>> > >>> With those 2 extra fields you essentially have access to > >>> everything that was recorded in the GPX file. > >>> > >>> You can also use Field Calculator to add more fields and > >>> populate them with calculation results. > >>> > >>> As an aside, Field Calculator cannot create new fields in > >>> the GPX file; instead it creates them as temporary virtual fields. > >>> > >>> A better approach is to first save the data in a shape file > >>> right-click on layer, choose Export > Save selected > >>> features then open that file instead of the original GPX. > >>> Field Calculator will add new fields to that format. > >>> > >>> Cordially, > >>> -- > >>> Garth Fletcher > > > > > > > > > > > > > > > > Roxo > > > _______________________________________________ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
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