[Qgis-user] GPX data in QGIS.
J. M
jimimckay at gmail.com
Tue Nov 3 07:36:44 PST 2020
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.vogelgesang at 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 <garth at 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 <jimimckay at gmail.com
> >>> <mailto:jimimckay at 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
> >>> <garth at jacqcad.com <mailto:garth at jacqcad.com>> wrote:
> >>>
> >>> On 10 Sep 2020 at 20:12, J. M <jimimckay at gmail.com
> >>> <mailto:jimimckay at 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
> >
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