Data conversion issues: GPX to shapefiles (episode 5)
So, i spent a little time this weekend remembering how to use Illustrator. MacGPS Pro will make a chart of elevations: i want the look and feel to match the other maps and diagrams i imagine (fantasize) making.
In all that exploring, i found:
1) The pdf export’s elevation line is actually many line segments, too small for using the “text on a path” function.
2) The auto trace function, when applied to a graph, traces the cells of the graph and does not make one continuous trace of the plotted elevation line.
3) When one uses the “text on a path” function, the styling previously applied to the path (a stroke, for example) disappears.
This does count as progress!
I then went to MacGPS Pro and cleaned up a track to document Lassen’s Main Park Road in order to get the elevation profile.
The 29 mile Main Park Road was constructed between 1925 and 1931, just 10 years after Lassen Peak erupted. Near Lassen Peak the road reaches 8512 feet, making it the highest road in the Cascade Mountains. It is not unusual for 40 feet of snow to accumulate on the road near Lake Helen. — NPS
That done, i extracted it and a collection of waymarks in kml and gpx format, in order to look at them in uDIG.
No chance. One can convert the KML (used by Google Earth) to GML (Geography Markup Language, presumably easy, albeit i’d prefer to find someone else’s stylesheet. However, kml export does not include the timestamps. That’s fine for this trip, since i lost the timestamps, but i’d prefer to find a conversion for the GPS exchange format, GPX.
It would be lovely if GPSBabel could help, but it handles the same formats i can export from MacGPS Pro and none that uDig can consume.
One possible solution was based on finding a question in a Quantum GIS (QGIS) forum: i have an old version of QGIS (”Io”) still on the laptop. The GPX files did not display in QGIS, but Google Earth loads the files, just fine. Christine and i suspected that some XML element for standard metadata may be missing and Google Earth just forgives and assumes a standard (like WGS84). Skimming the schema it doesn’t seem like that’s the problem: MacGPS Pro’s export seems to meet the spec. I would submit a QGIS bug report, but i’m using an antique version of the software.
Other solutions i’ve found tonight seem to be windows or linux based. If it truly hacked the open stack, i could possibly hack a solution.
A final side note: Google Earth is one of the applications that stores the user name as part of the path to the configuration files.
Dead end explorations after the cut:gpx2shp is promising, but i’d need to compile it for the Mac. This may be a good gift to give to the community, but i don’t have the time this week.
GDAL is raster, not vector. And i don’t really “Hack the Open Stack” even if i have a t-shirt from Where Camp that makes that claim.
OGR looks right — it’s vector and the right formats are listed.
The way to use OGR is FWtools – -which is just windows and linux.
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Tags: Illustrator, MacGPS Pro, uDig
