[pct-l] computer/droid help

[AsABat]

Backcountry Navigator can download USGS and My Topo maps free within the app. With this and Halfmiles gpx files all you'd be missing is the PCT trace where the USGS maps don't show the trail.	The waypoints every half mile mitigate this to some extent. 

If Halfmile didn't go and get and Windows phone we'd have it made!

AsABat
PCT Water Reports SoCal http://pct.4jeffrey.net
Send water updates to water at 4jeffrey.net

lancem at wvi.com wrote:

>Scott,
>
>>From my little bit of experience I can share this,
>
>For a map image to be used by GPS software, calibration data must
>accompany
>the image so the software knows the latitudes and longitudes
>represented on
>the map.
>
>Calibration data for raster images (jpg, bmp, png, tif, and others)
>assigns
>specific latitudes and longitudes to a few spread out pixels in the
>image. (A
>digital camera generates jpg images.)
>
>The GPS software uses mathematical algorithms to interpolate the
>lat/lon of
>all the other pixels.  This is how the software is able to place
>waypoints and
>display moving maps.
>
>Another issue is file size.  Often GPS software will chop images into
>smaller
>pieces (tiling) for better memory management.  For instance, a small
>map of
>1275x1650 pixels may be tiled into 300x400 pieces.  Halfmile’s maps are
>about
>this size.  A 7-1/2minute USGS topo might be 3200x4050 pixels.
>
>I assume all this applies to vector image files as well, but takes
>different
>software.
>
>The BackCountry Navigator home page article "Using Calibrated Digital
>Maps for
>Android Navigation" describes a way to calibrate and use your own map
>images.
>It looks like you would have to convert Halfmile’s maps from pdf to
>another
>format such as jpg or bmp then calibrate and tile each map using
>MAPC2MAPC.
>
>
>I've converted, calibrated, and tiled some of Halfmile’s maps for a
>Blackberry
>GPS application.  I used Omniformat to convert the pdf files to bmp
>files, Oziexplorer
>to calibrate and TBcutter to tile the images.  It takes 10-15 minutes
>per map
>after a bit of practice.  To do all of Halfmile's maps would take days.
>
>An easier solution is to simply load Halfmile's gpx waypoint files to
>your droid
>and carry paper copies of the map images.  If you need to know exactly
>where
>you are or where to go, many GPS apps can use the gpx files to tell you
>how
>far and in what direction it is to the nearest waypoint.  Then look at
>your
>map for that waypoint and follow your compass.  
>
>-Lance 
>
>
>
>
>
>WVI WEBMAIL - http://www.wvi.com
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