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Author Topic: Navigation Charts  (Read 4429 times)

truckie

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Navigation Charts
« on: December 26, 2010, 07:26:12 AM »
Are there any plans to include coastal Nav charts to the list of available downloads?

Thanks

jbensman

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Re: Navigation Charts
« Reply #1 on: December 26, 2010, 11:12:40 AM »
My Trails have tens of thousands of NavAids along some parts of the coast.  It also has boat ramps and marinias and some wrecks.  Anything I can find, I add.

A while back I looked at the ACOE's Inland Charts and tried to convert them into a map.  I did not know or understand what the vast majority of the shapefiles where and lots of stuff overlapped.  I was never able to get it figured out.  Some of the stuff on the charts I was able to figure out and I added it to My Trails.  Someone who understood water navigation could probably figure it out.

truckie

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Re: Navigation Charts
« Reply #2 on: December 26, 2010, 01:15:16 PM »
Thanks, I'll check that out.  Do you know if they include bathymetry (depth scale) gradients?


jbensman

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Re: Navigation Charts
« Reply #3 on: December 26, 2010, 02:21:52 PM »
No My Trails does not have the dept contours.  But when looking for data for my trails I have come across bathymety data many times.  Dept contours never seemed appropraite for My Trails (and I tried a few times and I got way too big files).  It seems more appropriate for the state/regional topo maps.  Where are you from?  Maybe you could talk somone into adding it to a state topo map. 

Since I was finding so much bathmyetric data and none of the maps I am aware of have it, a couple of times I have thought about creating a bathymetric overlay map.  But being from the midwest, it has never risen very high on my to do list.  Many state GIS sites have bathmetry data on them.

maps4gps

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Re: Navigation Charts
« Reply #4 on: December 27, 2010, 08:11:03 AM »
What specifically are you looking for?

NOAA makes most (all) of their charts available in both raster and vector format.

Garmin size limit on 'Custom (raster) Maps' is very limited.  Many charts would need two files and you need a computer, etc. to rename them on the GPSr.  Also one of the newer GPSr models which can display raster data.

Be aware that marine and land maps use a different base for sea level.  Bathymetry can be quite different for the same area on charts of a different scale.  I have seen areas where the coast on a detailed NOAA chart is located a 100+ feet above sea level on the NED elevation from USGS.  Contouring one of NOAA's gridded bathy data sets will add more uncertainty.

From NOAA's website: '... much of the depth information found on NOAA charts is based on surveys conducted before 1940, the shoreline is more than 20 years old ...'  

« Last Edit: December 27, 2010, 09:19:19 AM by maps4gps »

-Oz-

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Re: Navigation Charts
« Reply #5 on: January 08, 2011, 10:20:44 PM »
These maps are very difficult to make because of what maps4gps is saying; accurate data is hard to come by... data for lakes is nearly impossible in a lot of cases.
Dan Blomberg
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