In order to emuate upmain / downmain / uptrib / downdiv navigation we need a crude implementation of network traversal that follows a least-cost path at every node.
Using nhdplus attributes, we need to follow the lowest divergence value at every downstream junction for down main and the lowest stream level in the upstream direction for upmain navigation. The 3DHP flownetwork simplifies this with the upmain / downmain logical values.
In order to emuate upmain / downmain / uptrib / downdiv navigation we need a crude implementation of network traversal that follows a least-cost path at every node.
Using nhdplus attributes, we need to follow the lowest divergence value at every downstream junction for down main and the lowest stream level in the upstream direction for upmain navigation. The 3DHP flownetwork simplifies this with the upmain / downmain logical values.