[Qgis-user] Newbie

[Bernd Vogelgesang]

In short:
Metric Coordinate System
Buffers
Polygons to lines
Save as GPX with CRS WGS84

I assume that you already use a metric coordinate system (DHD Gauss Krüger  
4 or ERTS89 UTM 32N ?), cause you wrote that you digitize your waypoints  
and I assume you have some background map for this.
Working in metric system is crucial, otherwise your buffer units wont be  
meters but degree and your buffers would go all around the planet.

Usually I use the Processing toolbox (Verarbeitung -> Werkzeugkiste) for  
this kind of works and not the default vector tools, cause there you only  
produce temporary layers which frees you from saving each step as a real  
file until you figured out what and how to achieve things.
First, switch the toolbox interface from simplified to advanced (bottom of  
the box)

Search for "buffer" in the toolbox.
Pick "Fixed distance buffer" and in the dialog select your waypoints  
layer, set your radius and decide whether the buffers should be dissolved  
or be individual circles. For nicely curved circles, rise the number of  
segments to e.g. 15 (more points!), if it doesn't matter leave the default  
5.
What you get now is a polygon layer with your buffers, but to be able to  
convert them to a GPX file, you need lines (GPX can't handle polygons)

So again in the toolbox search for "polygons to" and pick the tool  
"polygons to lines" from the SAGA functions.
Hopefully, SAGA is activated and functional in your install (check under  
Processing -> Options -> Providers -> SAGA)
You could also pick the QGIS function with the same name ( a lot of  
functions here have multiple implementations by several providers)

Right-click your lines layer in the Layers List and choose "Save As .."

Format: Choose GPS eXchange Format [GPX]

CRS: click "Change ...) and set the CRS to WGS84 (EPSG 4326)

In case you use a recent version of QGIS (recommended) the other settings  
should be ok.

Click "Browse" to select the destination path and file name for your GPX  
file.

Now it's up to your GPS-device to eat this file or not ... newer Garmins  
directly process gpx files, for older ones you probably need to connect  
the device with GPS plugin.

Hope this works


Cheers
Bernd


Am 18.11.2014, 22:06 Uhr, schrieb Randal Hale  
<rjhale at northrivergeographic.com>:

> Hello - So to get a circle which we call a buffer: Vector Tools ->  
> Geoprocessing Tools -> Buffer Of course you need to know what projection  
> your original data is in - if it is in WGS84 the buffer tool won't give  
> you the desired results (but will still create a buffer).
>
> QGIS has GPS tools - but I haven't used them very much (PLugins -> GPS  
> Tools after checking it look for GPS Tools under the vector menu). I  
> have used DNR GPS to upload GPX files into a GPS Unit....of course that  
> also depends on your GPS unit (but it is possible).
>
> I hope this starts you in the right direrction.
>
> Keep asking questions!
>
> Randy
>




>
>
>
>
>
> On 11/18/2014 03:24 PM, Philipp Pfeiffer wrote:
>> Hello together,
>>
>> I´m working as a biologist in Germany and therefore I just startet to  
>> get to know QGis and I really think it´s an excellent tool. But of  
>> course there will be always things that I just can´t figure out by  
>> myself.
>>
>> I have a couple of waypoints and it´s no problem to digitize them or  
>> upload these to my GPS device. But before I want to upload I have to  
>> create a specific area around these waypoints (in form of a circle)  
>> with a certain radius (500m). How do I start to create this circle and  
>> secondly how do I convert this circle to a track that can read my GPS  
>> device ?
>>
>> I hope you understand my question and can give me an answer.
>>
>> All the best and many thanks.
>>
>> Kind regards
>>
>> P.Pfeiffer
>> _______________________________________________
>> Qgis-user mailing list
>> Qgis-user at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/qgis-user
>


-- 
Bernd Vogelgesang
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91083 Baiersdorf/Igelsdorf
Tel: 09133-825374