[gdal-dev] creating graph for single line shape layer using gdal gnm

[Mikhail Gusev]

Hello, hema.
The current default implementation of GNMNetwork::AutoConnect() can work
only if the passing array of layers contains at least one point and one
line layer (i.e. GetGeomType() for the layers equals wkbPoint and
wkbLineString accordingly). For each line feature the algorithm takes the
start and end snapping area formed around the start and end point of the
line and searches the points from point layers which are situated inside
these two areas. So there is no way for now to connect features of only one
line layer automatically. You can use ConnectFeatures() to connect
manually, but you will need the features (with any geometry!) to be the
source and the target for the connection, while the gnm_roads_line feature
will be the connector.

2014-11-11 11:26 GMT+04:00 yhema <hema.yeedunuri at amigooptima.in>:

> Hello all,
>
> I am trying to create a graph for network analysis using gdalgnm.The
> feature
> auto connect is working if we provide more than one layer.How can we
> connect
> features of a single layer so that graph is created automatically. We can
> connect features using connect features but automatically it is not
> conncting using auto connect .Here is the code.
>
>  char **options = NULL;
>     options = CSLAddNameValue(options,GNM_INIT_OPTIONPAIR_NAME,
> "roads_network");
>
>
>     GNMGdalNetwork *poNet;
>
>     poNet =
> GNMManager::GdalCreateNetwork("/home/shiva/Desktop/network/network_data",
> "ESRI Shapefile", "EPSG:4326", options);
>     CSLDestroy(options);
>     if (poNet == NULL)
>     {
>         printf("Failed to create network\n");
>         exit(1);
>     }
>
>     GDALDataset *poSrcDS = (GDALDataset*)
> GDALOpenEx("/home/shiva/Desktop/network/data",
>                                                      GDAL_OF_VECTOR |
> GDAL_OF_READONLY, NULL, NULL, NULL );
>     if(poSrcDS == NULL)
>     {
>         printf("Can not open source dataset at\n");
>         exit(1);
>     }
>
>     OGRLayer *poSrcLayer2 = poSrcDS->GetLayerByName("roads");
>     if (poSrcLayer2 == NULL)
>     {
>         printf("layer is null\n");
>         printf("Can not process layers of source dataset\n");
>         exit(1);
>     }
>
>     GNMErr err2 = poNet->CopyLayer(poSrcLayer2, "roads");
>     if (err2 != GNMERR_NONE)
>     {
>         printf("Can not import layers from source dataset\n");
>         exit(1);
>     }
>
>     GDALClose(poSrcDS);
>
>
>     if (poNet->CreateRule("CLASS gnm_roads_line COSTS TIGER_ID") !=
> GNMERR_NONE)
>     {
>         printf("Can not create rule\n");
>     }
>
>     if (poNet->CreateRule("NETWORK CONNECTS gnm_roads_line WITH
> gnm_roads_line  ") != GNMERR_NONE)
>     {
>         printf("Can not create rule\n");
>     }
>
>
>     printf("\nBuilding network topology ...\n");
>     GDALDataset *poNetDS = poNet->GetDataset();
>     OGRLayer **layers = new OGRLayer*[3];
>
>     layers[0] = poNetDS->GetLayerByName("gnm_roads_line");
>     layers[2] = NULL;
>     layers[1] = NULL;
>
>
>     if (poNet->AutoConnect(layers,0.05, NULL) != GNMERR_NONE)
>     {
>         printf("Building topology failed\n");
>         exit(1);
>     }
>     else
>     {
>         printf("Topology has been built successfully\n");
>     }
>
>     delete[] layers;
>
>
>         GNMManager::GdalCloseNetwork(poNet);
>
>
>
>
> thanks,
> hema
>
>
>
> --
> View this message in context:
> http://osgeo-org.1560.x6.nabble.com/creating-graph-for-single-line-shape-layer-using-gdal-gnm-tp5172326.html
> Sent from the GDAL - Dev mailing list archive at Nabble.com.
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