I need to draw and merge multiple vectors into a polygon

[TimBranan]

I have to draw a polygon around a very large area of water consisting of many islands and shoreline.

its far too large to draw in one shot, so I figured I'd have to draw many vectors as I go, then merge the vectors into a single one and fuse the endpoints of the lines into a single continuous line, that would eventually consist of a single polygon enclosing the body of water.

the problem is I don't know enough about the tools in this regard to actually do it.

I tried drawing a couple of shapefiles, then merged them together, but the attribute table still treats them as two separate lines, rather than one, and digging around in the help files and knowledge base hasn't shown me how to do that, probably because I don't know the right wording.

so to break it down, I need to:

1. draw many vector lines

2. merge them into a single vector line

3. make sure there are no breaks in the lines where the multiple lines were merged together.

4. turn the line into a polygon, accounting for negative spaces where there are islands. I assume I can draw a polygon around the islands and merge multiple polygons together and flag them as empty space, somehow.

thanks for any help.

Tim

[DarrenWiens2]

The main tool you're missing is Dissolve, or Editor Merge, both of which may combine multiple features into a single feature.

I'll draw your attention to the Unsplit option in Dissolve - if checked this will only dissolve lines with an end point in common, which will aid you in finding those that may not have snapped during digitization.

[TimBranan]

I tried the dissolve tool on my test data and it just deleted one of the two segments, rather than merging them. I used the objectid to merge on.

[DarrenWiens2]

Dissolve should never delete a feature. Run Dissolve with no feature selection, otherwise it will only consider the selected features. Make sure you've saved your edits before running the tool, otherwise it may only consider the saved features. Also, you select attributes if you want to group the output. Since you want everything dissolved into a single feature, do not select an attribute to dissolve upon.

[TimBranan]

I left everything unchecked and it did as directed, so that's one step down.

[LukeSturtevant]

Do you have a shapefile of the islands or are you just trying to draw a polygon around the islands as seen on aerial imagery? Is there a reason why zooming way out and drawing a single polygon isn't working?

There are several standard tools in the editor toolbar for this. There is a merge tool and an explode​ tool that allows you to merge multiple features. You can then use the explode tool to see if more than one segment exists and fill in any missing segments. You could then use the feature to polygon tool.

Another way to do it is once you are done drawing your lines you could use the dissolve tool. To make sure you didn't miss any sections you could use the multipart to single part​. If that tool turns out more than one row then you know you have a section that you need to fill in. After you get a closed polyline feature you can run the feature to polygon tool mentioned earlier.

[TimBranan]

I'm drawing the shoreline based on imagery.

I can't zoom way out because there would be too much loss of detail. I'm talking about thousands of miles of shoreline. it needs to match the shoreline pretty closely, not just an approximation, so I have to get in pretty close, which is going to mean hundreds of segments.

[LukeSturtevant]

Ahh okay yeah I've had to do that before it's a pain. I would just make sure you have snapping on specifically end point snapping and then select the lines and merge them periodically using the editor toolbar.

[TimBranan]

how do I merge the two endpoint verticies into a single vertex to assure there is no break in the line?

the dissolve joined the two lines, but doesn't do anything about the break, even with one snapped to the other beforehand, as best I can tell.

[LukeSturtevant]

I'm not sure what you mean by a "break". Is there a visible break? If it appears to be snapped correctly have you tried to run feature to polygon to see if it generates a correct polygon?