There is one more functionality I would like to add in this control, trace polygon in another direction by pressing shift/ctrl. If any more suggestion please let me know.

GeometricNet is still in nascent stage, many more concepts and functionality need to be incorporated. My purpose of hosting the alpha code was that I would be getting the feedback from developers on this project. So that improvements can be done. I am getting a good feedback and improving the same. Still the project is not in the state to be directly used by the users, but developers can use this or part of this project for any network related project.

Here is a sampel code how rtree can be utilized to index all of your POIs

from rtree import index
# locations=array of {id:1,coordinate:(x1,y1),name:"htel abc"}
def create_index(locations,index_name):
	idx=index.Index(index_name)
	for location in locations:
		id = location['id']
		x = location['coordinate'][0]
		y = location['coordinate'][1]
	idx.insert(id,(x,y))
	del idx

In this sample a function create_index just loop through all of POIs and create a rtree index. It creates index files with index_name (index_name.idx and index_name.dat). So when you want to search the nearby location you load index with these files. The next sample code shows how easily one can find the near locations.

# returns list of ids
#coordinate - (x1,y1), count - no of ids to be returned
def find_nearby(coordinate,count,index_name):
    idx = index.Index(index_name)
    x = coordinate[0]
    y = coordinate[1]
    return idx.nearest((x,y),count)

So keep indexing your locations and find nearby very easily.

In this implementation i.e UndoRedo class has two stacks for undo features and redo features. On any edit of vector feature I insert the feature in undo stack. Like if there is a update of the feature the old feature get inserted into undo stack. So on undo action the updated  feature is  moved out to redo stack and old feature is moved to layer. The only issue here is with delete feature, openlayers library on delete action does not remove the feature (as it is required to send that info to server on commit) but change the state to “Delete”. I have done a little modification on delete, I remove the feature from layer to undo stack. So at this stage if somebody commits, the deleted features would not be deleted from server. To over come this issue I’ll write a function that will move back the deleted features to layer with state  “Delete” and style {display:”none”}  so that deleted features could also be removed from server.  This function has to be triggered before commit i.e. on start event of save strategy. I’ll update this control with this function by that time please test undo redo control example and in case of any bug let me know.

Please check the example – modify network where user can select a tool “Move Node” from tool panel and select any existing node and move it to the required position. The connecting edges to this node are also moved simultaneously with node movement. After modification you can save your modification with save tool.

Some more examples of Geometric Network (GeometricNet)

Basically I create a point feature and set the angle attribute of this feature same as of the line at that position. And position of point/direction-arrow could be start, end or middle of the LineString or segment. For each segment of linestring  a arrow can be added. Not shown in the  example but the position can be set any where on the linestring by giving the measure value (between 0-1) to the function “getPointOnLine( )” in Direction.js

Now I have created a example for electrical network. Here a existing network of power distribution is loaded in the window along with many network creation tools. Functionality of utility network are simulated here with this examples. Like a distribution  line can not start from substation, only high voltage line can start.  Another constraint is  from a pole one can take fixed number connections, so I have consider four and only four line can be drawn ‘to’ connection points. As electrical network is directed network, so a line can not be drawn ‘from‘  connection point to pole. There are many other Utility GIS functionalities are implemented like while drawing edge (electrical line /wire ) default end node (poles / network element ) , splitting the edge if another edge touch the same and check the edge to edge snapping rule. Please explore the more in the example.

I am not electrical engineer so all rules are with my basic understanding of electric network / power distribution. So to tackle this issue is very essential, like all GIS software, utility GIS  or AM/FM/GIS software are developed by software engineer or non domain expert. Here I have designed a configuration file that contains all the network behavior.  So by using this configuration file, I separate the domain expertise from GeometricNet library.  This  configuration file tags are self explanatory and simple.  Further to this, I am working on feature modification of  the network.

By drawing  a edge network with draw edge tool, it will create network topology itself.  The graph is implemented with modified adjacency list data structure. By drawing the flags near any two nodes initiate the process to find the shortest path between these nodes. The shortest path is shown by selecting the edges of the path.

Right now project is in alpha stage. But developers familiar with OpenLayers can use this project easily.

Network topology or geometric network is a set of connected edges and junctions, along with connectivity rules that are used to represent and model the behavior of a common network infrastructure in the real world. Water distribution, road network, electrical lines, gas pipelines, telephone services, and water flow in a stream are all examples of resource flows that can be modeled and analyzed using a geometric network.(Source ESRI read more …)

My idea is to create geometric network with OpenLayers.How i have done, basicaly there are two layers Edge and Node extended from Vector Layer class of OpenLayers. Vector layer can draw the edge feature that inherits from Feature.Vector class of OpenLayers. If a edge is drawn associated nodes are created automatically and if node is added edge is splited. The association between edges and nodes are maintained any time. In a network connecting edges to a node or vice-versa can be found easily.

Here is the demo to show the network creation with OpenLayers

This demonstrats drawing of the network with correct topology. For example to draw the road network with edges and node that are associated to each other. The following abilities are shown here:
- draw edge; draw node only if it intersects with network
- draw node on edge and split the edge at that point
- draw edge intersecting the existing edge(s), create a node at intersection as well as split the edges
- maintains the edge-node network topology, while splitting the edges or adding the node.
Move mouse over the feature to see the network properties in text box.

I would  expand this work in following direction
- serializing and serializing of this data (or objects)
- how this network data can be utilized to create graph  and to find shortest path