Hmmm. Let me describe the whole reason I became interested in GPX. Then perhaps you will see how things fit together.
I am interested in putting together a tool chain to help improve Open Street Map. This is an area of interest to me because I think Open Street Map demonstrates the power of collaborative mapping with low-cost tools. In order to understand how the mapping process could be improved, I started to collect my own data for OSM. This sounds pretty simple. You just go out with your GPS data collector, collect some waypoints at road intersections and then...now what? I started copying waypoint coordinates by hand and using this to construct map features in OpenJUMP. Then I thought to myself, "This is nuts. There has got to be a better (faster) faster way to convert waypoints into features." That's when I found out about GPX. I've got a free (not open source) program that can download waypoints and tracks from my Garmin GPS receiver and output them in GPX format. What I've got now is a module that will allow me to import waypoints and tracks into OpenJUMP. I'll do some data manipulation and cleaning in OpenJUMP, and then I'll export the features I've created from my GPS data in the OSM XML format. (Here is an example of the processing I'm talking about: Adding standard feature attributes with default values. These will later be converted to OSM "tags". Here is another example: Taking a GPX track with a node every 25 feet and reducing the number of nodes based on the amount of direction change between segments, making the track "straighter".) I don't have any need for a map projection in this process. My input data is in lat/long, my output data will be in lat/long, and none of the processing that I will do requires calculations on the plane. I'm not computing areas, I'm not measuring the distance between buildings in meters, nothing like that. I'm simply creating features. Now, I may do some simple geometry editing. Things like trimming one feature based on the location of another feature, or creating a point feauture based on a start point, an azimuth, and a distance. But all of that can be done with a "geodetic calculator". Here is where the map projection fits in: When someone downloads my OSM data so they can produce a map of their neighborhood, they will want to select a map projection that fits their particular needs. Now, I suppose one could argue that I should convert my lat/long data to a projected plane system when I import it into OpenJUMP for processing, and unproject it before I export in OSM format. But I wonder if that is really going to be worth the effort. After all, I'm working with waypoint data. It's not exactly survey grade data to begin with. I think it might be more helpful to relate the coordinates I'm seeing on my OpenJUMP map view with the coordinates I'm reading from my GPS receiver. Landon On Thu, Nov 20, 2008 at 7:52 AM, Adrian Custer <[EMAIL PROTECTED]> wrote: > On Thu, 2008-11-20 at 07:39 -0800, Sunburned Surveyor wrote: >> >> In this particular scenario unprojected lat/long data is exactly what >> I need. I'm not producing any maps at this stage in the game. I'm just >> collecting position data using GPS. My data will be available for >> other people to make their maps. They can take my lat/long data and >> project it into whatever coordinate system works for them. >> >> ... JTS is just serving as a convenient >> coordinate holder at this point. >> >> The Sunburned Surveyor > > so I'm back to being confused, where does OpenJUMP come into the > picture? Are you not really using OpenJUMP either? > > --adrian > > ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Geotools-devel mailing list Geotools-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/geotools-devel
