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
<rjh...@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
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