Quality Control Your River Network
IT IS STRONGLY RECOMMENDED THAT YOU READ ALL OF THIS WEB PAGE BEFORE CONTINUING!
- RivEX will fail to process a network which is not topologically correct, thus quality controlling your river network is an important step and should not be ignored!
- If you have read the File Structure section of this manual you will know that output of a quality control is a dBase file identifying polylines that have failed the specific quality control.
- This section of the manual gives instructions on how to use the quality control tools and provides advice on how to deal with various errors. The more unusual errors (e.g. a multi-part polyline pointing in on itself) will be identified by the RivEX data dictionary building process before the main interface displays. If this is the case you will not have access to the quality control tools as this is a bizarre error needing manual intervention!
- RivEX does not attempt to automatically fix problems, it only identifies them. The reason is simple, a problem can have more than one solution and the solution depends upon seeing the "bigger picture" which only you the user has. To allow the GIS to automatically fix errors can sometimes lead to even more problems!
Check your network for:
Check your MEASURED network for:
The ramifications of editing a network. . .
- If you have identified various errors and tweaked the shape of the polylines, moved polylines, split polylines, exploded multi-part shapes and snapped everything correctly, then you will have a network ready for RivEX to process.
- But . . . the problems start when other information references your old uncorrected network!
- For example, you have identified a short, 2 vertex polyline and deleted it. You will have snapped the other polylines to a single node to ensure network connectivity. By snapping the lines you have moved them. Other aligned data (which could be points, lines or polygons) representing sampling sites, GPS locations, or administrative boundaries will now either intersect or not.
- Information encoded into the polyline may not be valid anymore. PolylineM values will require recalibration if you have shortened a polyline by removing a vertex that was causing self-intersection.
Always work from a backed up copy!
You have identified many errors, how do you visualise them?
- You have identified many errors (e.g. 50+) and need to visualise them so you can edit them. You can achieve this in several ways. One such method is to join the tables.
- This is a temporary link between tables whilst ArcMap is running. To see how to create a join click here.
