Wednesday, October 21, 2009

Raster pictures on my Oregon

A couple of days ago, we had a search in Highland Forest Park, NY. Stryder, my dog never got out of the truck, as the victim was found by the Sheriff's department trailing bloodhound, but since I had the time, I started making a raster map of the park fr my Oregon. I quickly took a couple of digital pictures of the park's trail map, two maps, one for snowshoeing trails and the other for x-country ski trails (they are getting ready for winter fun).

I did not change the camera's settings (6 megapixel camera) when I took the pictures. That gave me files of about +/-2.5Mb. Georeferencing with Google Earth was ok, but I really prefer the quick method that Topofusion has, just click on 3 points on the layer and the base map/aerial. Much simpler, quick and easy. I talked to Scott of Topofusion about making kmz layers with TF, especially as if I download the maps prior to leaving home, I can then use TF even without internet access.

The screen dump below is of the 2.5 Mb file

This screen dump is with a jpg taken at 2 megapixels resolution giving a kmz file of +/-950Kb. The map is a 24K topo map in both these pictures.

This last picture is the same as above the only change being the map, this time it is the Garmin Topo 2008.

I noticed that the re-draw of the screen is faster with the smaller kmz files, but still the 2.5 Mb files were quite usable. That means that if I have to do some hasty work and don't reset the camera back to 2 megapixels, the results are not going to bite me back. Actually the lesser trails show better on the larger files and since I would be moving at pedestrian speed, screen redraw speed is of lesser importance and it is more important to me to better see the secondary trails too. I also have ample room on my 8GB uSD card.

Another lesson learned is that when you have two kmz files of the same area, only one shows on screen. I have not managed to find out the reason why  one has precedence. The only solutions I see for now are either move one file off my uSD card (needing a computer -which I have in my truck) or putting them on two different uSD cards (and try not to lose/misplace those - good luck).