American users can take advantage of the free data available at the US Geological Survey website as part of the National Hydrography Dataset.

Data is available for thousands (if not millions) of lakes in the US, in the form of shapefiles. These files can be selected on the website, downloaded and imported directly into ReefMaster for use as shorelines in map projects. We don't make any claims as to the quality of the data (and nor to the USGS), but the high-resolution shapefiles available seem to be a generally reasonable quality, and would certainly make a good starting point for many map projects.

Be warned - the website is a bit clunky, and the download process is a bit tedious - you have to submit your email, and wait for a download link to be sent to you.

Here's a brief overview of how to do it:

• Go to the NHD Viewer webpage. Note that I have had some troubles using Chrome on this site - Firefox seems to work OK.
• Pan and zoom the map until you find the lake you are interested in.
• Check the Hydrography layer in the layers panel, and put the mouse mode into identify mode (circled).
• Draw a region around your lake.

• After the application does a bit of work, the features within the region should be identified.
• Open the Selection tab at the left, and expand the Hydrography section.
• Find your lake, with a feature-type of Water Body and click download.
• Choose Hydrography and the shapefile option (the one without Flow) in the next two windows.

• Click Check Out and enter your email. Once the download link arrives, cut and paste this link into your browser to download the zip file. Extract the files from the zip and store them somewhere on your hard drive.[/i]
  
• Create a new project in ReefMaster, and click the Import Boundaries button in the Boundaries panel. The file you want is in the hydrography sub-folder of the zip-file you downloaded.
• The boundaries will be imported. There might be a bunch of other lakes etc around the lake you wanted - these can be deleted within ReefMaster. Make sure to set the boundary type of the main shoreline to Shore.

Is it possible to use this to download creek or river channel paths?
I've got a lake that, when I zoom in on it, isn't visible outside of an aerial photo. (DMS: 40° 41' 10.297" N, 91° 59' 42.315" W)

There are just so many download and file options here that it's kind of a needle in a haystack situation for a novice like myself.

I uploaded a boundary for another lake and the shoreline file also included boundaries a lot of little nearby ponds.
Figuring out which one to keep and which 159 to delete was a bit of a time eater.
Is there a quick way to identify which boundary is which when you have multiples?

Probably the easiest way is to load your downloaded Shapefile into QGis and then select the shoreline(s) you want. You can then save them again in a file with only those. It can also be useful if you need to modify very large polygons (e.g. a river outline) - then you can cut it to the size you need in ReefMaster and re-save it.

This data can also be found on the USDA Geospatial Gateway. Pick your state and county of interest, then download the 12-digit watershed boundary data set under the "Hydrologic Units" section. It's by county though, so other bodies of water are included as well. Besides having multiple bodies of water in the same file, an additional issue I ran into was the data for my lake had both shoreline boundary and island data in one file. This confused RM and the results were messed up.

To get around this, I loaded the shapefile in QGIS, exported to KML, opened the KML in Google Earth and zoomed into the body of water of interest. I right clicked on the shoreline boundary and selected properties. The associated entry (out of hundreds in that county's folder entry) is then highlighted in the left menu. I then closed the properties window, right clicked on the highlighted entry in the left menu and selected "Save As" and saved to KML.

Using notepad++, I then edited the KML directly. The longest set of points was the boundary, which I copied to a separate polygon KML file. Then I took all the island boundaries and combined them into another separate "folder of polygons" KML file. I had to edit the KML code a bit, as the islands were originally designated as "inner boundaries", and they had to be changed to polygons. I used the "Search" and "Replace All" functions in notepad++ to do this fairly easily.

Then in RM, load the boundary file first, go back into the edit menu, and set it to "boundary", then import the islands file. My island file was 97 boundaries, and RM took about 15 seconds to load them all. The default setting is "island" in RM, so I didn't have to make any further changes under the "Edit" menu.

What if we draw a map which an polyline that is not closed as shoreline? How to deal with it?

ReefMaster will close it for you, which may or may not be what you want.

Hi matt
Have you found anything like this for Australia?

@Norton79


This only works for Navico plotters (at5 files).

I have a Simrad plotter and use files from this site to give me an Aussie background map. It has some navigation aids (but NOT all) so would still need to refer to a more accurate source for navigation. It will not give you a "shoreline" as discussed above but I find it is enough for me.

wiki.openstreetmap.org/wiki/AT5-OpenSeaM...owrance_Simrad_B%26G

Australia map

I finished up using Open Street/ Open Sea map in combination with a hand drawn coastline from Google Earth. I've only drawn the parts of the coast that are adjacent to the areas I map as the whole coast is over 4000 km long....

Here's the wiki entry containing the links to the downloadable ocean files - wiki.openstreetmap.org/wiki/Coastline.

Explanations about geometric objects below are simplified to describe the spirit of the structures. OSM's data organization is contextual.

The IMC's ocean extract can be hit or miss for a couple reasons.
* When Geofabrik clips, they cull all polyline features by the poly file.
* In unusual cases, there isn't any shoreline in the file.

Ocean does not exist as a polygon within OSM. Ocean is generated by combining all the shoreline polylines. The IMC is capable of creating an ocean but only if a shoreline feature exists and the shoreline features is a closed polygon or extends all the way to the edge of the rectangular extents that are identified in the file. Even in cases where ocean is generated, areas outside the poly file may be misidentified due to shoreline exclusion. For these reasons, ocean generation is optional within the IMC.

Edit - OpenSeaMap also generates At5 files - wiki.openstreetmap.org/wiki/AT5-OpenSeaM...owrance_Simrad_B%26G