[GRASS-user] Stream order for vector networks

[Johannes Radinger]

Hi,

I am interested in calculating stream order (Strahler, Shreve) for stream
networks based on GRASS vector networks (e.g. created by v.net) without
using the raster approach of the GRASS add-on r.stream.order. Therefore, I
came across following paper:

Gleyzer, A., Denisyuk, M., Rimmer, A. and Salingar, Y. (2004), A FAST
RECURSIVE GIS ALGORITHM FOR COMPUTING STRAHLER STREAM ORDER IN BRAIDED AND
NONBRAIDED NETWORKS. JAWRA Journal of the American Water Resources
Association, 40: 937–946. doi: 10.1111/j.1752-1688.2004.tb01057.x

which also provides pseudocode to calculate Strahler order for non-braided
and braided vector networks defined by arcs and nodes. Thus, I am wondering
if it is possible to get the information from which node a specific arc
starts (from_node) and where it drains to (to_node). BTW, I seems some kind
of this information is already provided with the NC-dataset (FNODE_ and
TNODE column) in the streams attribute table, however I don't know where
this information comes from. Of course to extract this information the
network needs to be directed to define what is the upstream and what the
downstream node of each arc. However, having this information available, it
should not be to complicated to apply the algorithm proposed by Gleyzer et
al 2004. Thus I am interested to get 'from_node' and 'to_node' information
e.g. stored in the attribute table of v.net output?

Here the pseudocode provided by Gleyzer et al 2004:

########################################################################
MakeDictionaries(Network)
1 for each Arc ∈ Network
2 do FromNodesPerArc[Arc's ID] ← Arc’s FromNodeID
3 InflowingArcsPerNode[Arc's ToNodeID] ← InflowingArcsPerNode[Arc’s
ToNodeID] ∪ Arc’s ID
4 OriginatingNode[Arc's ID] ← Arc’s FromNodeID

StreamOrdering(ArcID)
1 Visited[ArcID] ← true
2 if | InflowingArcsPerNode[ FromNodesPerArc[ArcID] ] | = 0
3 then StreamOrders[ArcID] ← 1
4 else
5 for each Arc ∈ InflowingArcsPerNode[ FromNodesPerArc[ArcID] ]
6 do if not Visited[Arc]
7 then UpstreamOrders[Arc] ← (StreamOrdering(Arc), OriginatingNode[Arc])
8 else UpstreamOrders[Arc] ← (StreamOrders[Arc], OriginatingNode[Arc])
9 MaxOrder ← 0
10 MaxOrderCount ← 0
11 for each (Order, Origin) ∈ UpstreamOrders
12 do if Order > MaxOrder
13 then MaxOrder ← Order
14 MaxOrderCount ← 1
15 MaxOrderOrigin ← Origin
16 else if Order = MaxOrder
17 then if Origin ≠ MaxOrderOrigin
18 then MaxOrderCount ← MaxOrderCount + 1
19 if MaxOrderCount > 1
20 then StreamOrders[ArcID] ← MaxOrder + 1
21 OriginatingNode[ArcID] ← FromNodesPerArc[ArcID]
22 else StreamOrders[ArcID] ← MaxOrder
23 OriginatingNode[ArcID] ← MaxOrderOrigin
24 if SegmentIDsPerOriginatingNode[ OriginatingNode[ArcID] ] = nil
25 then SegmentIDs[ StreamOrders[ArcID] ] ← SegmentIDs[ StreamOrders[ArcID]
] + 1
26 SegmentIDsPerOriginatingNode[ OriginatingNode[ArcID] ] ← SegmentIDs[
StreamOrders[ArcID] ]
27 Segments[ArcID] ← SegmentIDsPerOriginatingNode[ OriginatingNode[ArcID] ]
28 return StreamOrders[ArcID]
########################################################################

Is there anyone having experience with that, or has already tried to
implement a vector-stream order approach in GRASS GIS. Specifically I am
interested
in Shreve stream order for simple (non-braided) stream networks and
Strahler stream order for braided river networks (Gleyzer et al 2004).

Best regards,
Johannes
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