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Humminbird branded locators in combination with Lakemaster/Humminbird map chips give you the option of adjusting depth contours relative to water levels, thus changing the safety shading.  This feature only works for the surveyed lakes on the mapping chips though.

Good stuff.  I have downloaded the files and information to begin working with them.

I downloaded and registered G-Raster, then converted the entire GeoPDF file into GeoTIFF, then .kmz.  Checked the accuracy of the .kmz with Google Earth and it was excellent.

Basemap loaded the .kmz and I created the river, creek, and roadbed trails easily; then exported them in the desired .gpx format.  Worked perfect on the Lowrance HDS and the trails aligned very well with previous know waypoints.  Mission accomplished.

Thanks for the help and the cost saving leads on Global Mapper.  Sounds like my next investment.  I really like G-Raster.  What a great program.

Thanks for the help and quick reply.  I downloaded a 1949 topo map from USGS's National Map Viewer and it was delivered in the GeoPDF format.  This is the first time I have worked with GeoPDF's.  Nothing I have will import them, including Fugawi.

I have manually created several trails in ExpertGPS and OziExplorer by tracing river channels on the topo map downloads built into those programs.  It takes a little time but works fine as long as the trail file can be exported as a .gpx.  Most marine locators will read this format.

If Global Mapper will open a GeoPDF, maintain the georeferencing, and allow the creation of a manual trail for .gpx export that would be perfect.

Being a new member, I first want to say hello and thanks for all the great information posted in this forum.  Wow!  I have worked with GPS units (many brands) for several years now, mostly gathering, editing and converting data (wpts, routes, trails). In the last couple of years I began working with custom mapping and I have a lot to learn.  I spend a lot of time on the water and in the woods hunting, fishing, camping and horseback riding.

My question relates to data extraction from GeoPDF files.  I have downloaded some vintage topo maps from the USGS for some areas that are now covered by lakes.  I would like to create a trail along the river and creek channels of the GeoPDF topo map then export it as a.gpx file for use on my Lowrance locators.  Ultimately, I would like to be able to view the entire contour map while on the lake.

I typically use ExpertGPS or OziExplorer to create trails, but I am not sure how to convert the GeoPDF file for use in these programs.  I also use Mapsource and Fugawi.  If it would be beneficial, I could purchase Global Mapper.

Any thoughts on how to create trails from the GeoPDF's would be greatly appreciated.  I also have a Panasonic Toughbook that I am setting up with GPS capability to use on the water.  This should be a better option than the Lowrance locator for viewing the entire topo map.