Mini tutorial ArcGIS 10 on how to perform automatic editing of the overshoot and undershoot polyline in ArcGIS 10 using topology rules (Rule of Topology) was written by Irwan, ST as a guest writer on iniGIS.com. Irwan is ir1gisplan.wordpress.com blog owners who live in Gowa, South Sulawesi, alumni of the University of Hasanuddin, Regional Development Studies Program and the City.
What is overshoot and undershoot?Overshoot and undershoot is one of the problems found by users who are involved in the analysis and route networks that utilize GIS technology. Overshoot and undershoot can result in network analysis does not run normally due to a broken line or cause excessive network analysis tools (network analysis) in ArcGIS considers polyline polyline is not connected with others who are in the vicinity. This resulted in the determination of direction, best route, Closest facility, OD matrix and form the output to a network analyzer (Network Analysis) its accuracy can not be responsible for.Definition of TopologyTopology is a mathematical definition that describes the relationship between objects relative to one object to another. In GIS, topology is defined by the user according to the characteristics of data such as polyline, polygon and point / point. Every rule has the characteristics specified data / rulecertain. Rule or the rule by default has been provided by the GIS software. (Sudomo Ostip, S. Si - PT. Duta Informatics)Topology Rules (Rule of Topology)To produce the correct data in accordance with the concept of GIS, ArcGIS provides the facility to perform checking filtering (query) errors automatically and do the editing (validation) spatial and attribute. Can imagine how long it would take if we make an error checking manually. Editing topology can be conducted simultaneously or one by one according to the type of rule that we apply and appropriate to the type of correction is done. (Sudomo Ostip, S. Si - PT. Duta Informatics)To make corrections to the undershoot and overshoot topology rules that we use is a "must not have dangles"Creating topology and topology rules
To create a topology, data formats that are used but not the data shapefile data in geodatabase format, so you have to process the data conversion to shapefile to the geodatabase format.Here are the steps to create a topology and topology rules in ArcGIS 10. The first step open feature dataset in ArcCatalog then right-click and choose New and select a topology as shown in the image above.
After that will appear like the picture above, click Next and then select the feature class that will be in the correction (in this example its class feature is the way), because the only way we will do so only correction feature class road course that we check.
The next stage is to add rules or additional rules topology, as shown in the image above, click Add Rule select the rule / rules to be used in this tutorial are minutes away "must not have dangle" do not forget to specify its class features (roads).
The result as shown in the image above. You can make a rule or other rules of good topology feature class with the same or a different feature classes. Click next then the result is as shown below.
Editing of data error checking results of topology
Add / append data to the geodatabase feature class and also topologynya it will appear like the picture above, pink is a data error either undershoot or overshot, but we need to know not all of the data error. End of line vertices will also be red because the think is not connected with other lines.
Start editing and switch on the Topology toolbar as shown in the picture above.Topology toolbar as shown in the picture below, click on "Error Inspector" (far right button menu).
In this example the visible appearance of Inspector Error 1516 errors exist, and then click the Search Now button menu then all the data errors will appear as shown below.
Select all all the data errors that appear on the Error Inspector window is. Right-click it will be available several options for editing existing data error is a snap, extend or trim. In this mini tutorial I chose the option Extend to perform editing on existing undershoot.
After determining the choice of editing that will be used, the next is to determine the value of Maximum Distance, a suggestion not to fill the maximum distance that is too big because it can cause lines to be edited to change shape and direction.
Note:Topology can only process Geodatabase format, while the shapefile format is not supported.To rule "must not have dangle" not all point error that appears is but the tip of a vertex or dangle down the road will also be considered errors occurred dangles so not everything should be resolved.Back to cross check to see ternjadinya errors, change the direction of the line, and line shape changes due to topology correction
