GPSFileDepot Forums

General Category => Map Making Support => Topic started by: Montwalleye on January 26, 2010, 03:10:43 PM

Title: lake maps
Post by: Montwalleye on January 26, 2010, 03:10:43 PM
 :) Okay thank you for explaining the difference between a segment and a map I tried a google search and looked on the Garmin site but couldn't figure it out. This might not be the correct forum but does anyone know of any water contour map sources, other than the Garmin ones, for my GPS, theirs doesn't cover several of the lakes I fish?
Title: lake maps
Post by: -Oz- on January 26, 2010, 03:12:17 PM
your best bet would be to google search for
lake name bathymetric data

and if you find any shapefiles let us know and we can put one together for you.  The data is hard to come by.
Title: lake maps
Post by: Montwalleye on February 12, 2010, 02:19:06 PM
You are right about the data being hard to find. I found one paper map that could be fit into a * 1/2" X 11" copy and I scanned it and saved it as a bitmap document, the lake has the same basic shape as on the GPS map but i can't see the lat. & long.. I was wondering if this has any use? I am also working with the Bureau of Reclamation and the Corps on Engineers to see if they have the data. The Bureau Rec has paper that they say they are going to convert to digital later this year will that be of any use?
Title: lake maps
Post by: maps4gps on February 12, 2010, 03:26:21 PM
To be of much use the data needs to be georectified.  With 4 + lat/long intersections on the image, this process will take a few minutes per image/lake; without them it could take considerable longer, or be next to imposible if the shape does not closely match another source with lat/longs.

How usable the Bureau of Rec digital files would be depends on what they mean by a digital file. 
If they georeferenced them, the image could be easily used on the CO, OR & DK units.
If they included vectorized bathymetry, it could be easily added in building a topo map, or an overlay/transparent mapset could be made from all the data they made available.

If they were non-georeferenced images, to digitize the bathymetry would take some time for a large reservoir; probably more time than anyone would care to do more than one or two.

Keep us informed.