I started playing around with OziExplorer and my newly-repaired Garmin Etrex Vista this evening. I went on a bike ride through some less-manicured areas of Singapore yesterday and wanted to work out a trail map.
Since there wasn't heavy jungle canopy, the GPS worked fine and I got a good track and set pertinent waypoints.
With only a few moments of twiddling (well-guided by the OziExplorer help file) I had downloaded the tracks and waypoints from my Garmin into OziExplorer.
I don't have a base map of Singapore (where can I find a digital base map of Singapore?) so I just called OziExplorer to create a blank map. Simple.
[My user experience so far suggests that OziExplorer was written by a GPS-Navigation enthusiast who added functions as he thought, "Gee, it would be useful to have function X." So far he's thought of everything that I want to do. The downer is, it's all organized in a somewhat non-traditional menuing and icon structure. It's idiosyncratic, but I am sure I can get used to it. (The icons are real eyesores, though -- way, way too busy) ]
I pulled up the base map and the map size was way too big. It had world map Lat/Long proportions. I started throwing away a few left-over waypoints from Canada, USA, Taiwan and Europe and reduced the map info to just local Singapore geodata. Then used the button called, "Rescale Map." It pruned the size, but still the few waypoints and tracks I had (a meandering, short 9 mile bike ride that probably was 3 miles diameter max) were still too small in scale to the map. They were piled right on top of each other.
Repeated rescans wouldn't make it any smaller, and my zoom was maxed-out at 750%. What am I supposed to do?
Consulting the help file, I found this troubling (?) explanation:
OziExplorer is Raster software (that is it uses images for the map, even the blank map is just an image). Zooming in on a raster image does not improve accuracy. The best a raster map can be calibrated to is +or - 1 pixel, when you zoom in at say 500% (x5 times) each pixel in the map image is increased 5 times, the accuracy of a position is now +or - 5 screen pixels. There seems little point in adding more zoom levels, as the calculations cause pixel rounding the liklehood of causing positional errors (on the zoomed screen that is) increases as the zoom level increases.
I do agree the blank map zooming could be improved as an image need not be used for that but to do that I have to rewrite quite a bit of the code and am saving that for a while.
So I don't know... Am I stuck from ever displaying a 3-mile diameter set of tracks in size large enough to read comfortably? It is sounding like I'm stuck.
Let's put it this way, I would be happy to sacrifice some accuracy in an image of my mapping data if I could zoom it enough to nicely fill a 8x12" paper map. It feels like OziExplorer is assuming that I demand absolute cartographic precision or nothing else. All I really want in this case is a trail map I can refer to now and then -- not a rigorous map.
If I'm forced to, I can always just save the map to an image, and then inflate it with Photoshop, but this is such a gross solution, and I'd prefer to do all my work inside OziExplorer.
Ideas?
Posted by Nils Blutig at April 7, 2003 09:54 PM | TrackBack